Panic in the North Atlantic
What are the Effects of Overfishing on Marine Ecosystems in the Northwest Atlantic Ocean?
Christopher D. Lampart
Community College of Vermont - Winooski
Abstract
This paper explores the negative effects that overfishing has had on marine ecosystems in the Northwest Atlantic Ocean. Overfishing is defined as “fishing with a sufficiently high intensity to reduce the breeding stock levels to such an extent that they will no longer support a sufficient quantity of fish for sport or commercial harvest” (as cited in Koster, What is Overfishing section, para. 5). The paper will provide a detailed history of overfishing in this region which will identify the causes of this problem. There will be a focus on the effects overfishing plays on marine habitat loss, bycatch, and marine food webs and biodiversity. Along with the environmental effects, the study will also examine the socioeconomic effects on humans, to help educate and bring relevant awareness to all people throughout New England, Eastern Canada and worldwide. The research gathered for this is drawn from government agencies, scientific papers, non-profit organizations, and previous studies; and will be analyzed through an ecosystem perspective. The goal of this study is to lay out the current impacts overfishing has on marine ecosystems so that new and improved solutions can be created and implemented in the near future; utilizing this research as its foundation. It should be noted that, for this paper, aside from mentioning specific fish species; fish will be described as to mean, “all organisms targeted and fished, all animals caught by humans, including fish, shellfish, and mollusks” (Pauly & Maclean, 2003, p. 4).
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Panic in the North Atlantic
What are the Effects of Overfishing on Marine Ecosystems in the Northwest Atlantic Ocean?
As it stands today, the global community faces a major problem with its oceanic ecosystems and fisheries (fishery is defined by Encyclopedia Britannica as, “the activity of harvesting fish, shellfish, and marine mammals as a commercial enterprise, or the location or season of commercial fishing”) in regards to the state of commercial fishing. The effects of overfishing are not only being felt by ocean-front populations; instead, international communities (including places like landlocked Vermont) of animals, plants, and humans are facing the consequences associated with this issue. Unfortunately, most humans are not aware of this problem and the scope of its impacts. Thanks to the high, readily available access to seafood and sea products, along with the glamorization of commercial fishing from Hollywood and television shows such as The Deadliest Catch and Wicked Tuna, it’s easy to see why the majority of the population has no idea of the crisis the planet is facing.
The question then arises, what are the effects of overfishing on marine ecosystems, specifically in the Northwest Atlantic Ocean? In order to thoroughly answer that question, this research will first examine and present in great detail the history of NW Atlantic commercial fishing, as well as identify the causes of overfishing in the region. Due to the complexity of the overfishing problem, this research will not examine the impacts on only one particular species, but instead will focus on marine ecosystems as a whole; presenting the effects through the lens of an interacting ecosystem (the ecosystem perspective). While this research will look at this problem from the ecosystem perspective, it is important to note that the codfish species will be discussed often throughout this research due to its high significance in this region and its role as the preferred global fish species of consumption for hundreds of years.
The following questions must then be analyzed and answered: What are the impacts of overfishing on marine habitats, what are the impacts in relation to bycatch, and what are the impacts on marine food webs and its role in biodiversity? While the environment suffers greatest from the negative effects; issues trickle down into humans’ social and economic realms, which further complicate the problem. Therefore, it must also be determined what the socioeconomic effects on humans are.
History and Causes of Overfishing
In order to fully understand the effects that overfishing has had on marine ecosystems in the NW Atlantic Ocean, one must first comprehend and visualize what this oceanic area looked like prior to its exploitation, along with the historical timeline of events that have contributed to the demise of these ecosystems. The physical, geologic make-up of the NW Atlantic sets the stage for these once lush marine ecosystems, filled with large populations of diverse animals and plant species.
Two significant, physical features helped contribute to the success of these ecosystems. The first, is the Mid-Atlantic Ridge, which is “an immense median mountain range extending throughout the length of the Atlantic, claiming the center third of the ocean bed” (Encyclopedia Britannica). This feature provides excellent life opportunities for species in the middle of the ocean. Greatly benefitting migratory species who utilize these areas as feeding grounds during their long voyage to and from the NW Atlantic.
The second notable feature is the continental shelf along the eastern seaboard of North America (particularly the coastlines of New England and Eastern Canada). “Continental shelves were formed in between glacial periods as the ocean flowed over the continents forming shallow areas along the coasts. They are an oasis in the ocean for plants and animals due to the abundance of sunlight, shallow waters, and nutrient packed sediment that washes in from rivers and wave action. The continental shelf in the NW Atlantic has provided 90 percent of the fisheries production in the region” (MarineBio Conservation Society, n.d.).
The exploitation of fisheries in this region begins at the time of Europeans arriving in the “New World.” For centuries prior to the Europeans’ arrival, coastal Native American tribes such as the Inuit, Mi’kmaq, Wampanoag, and Narragansett (among others), were the only people utilizing these fisheries. However, there is a stark contrast between the way the Natives and Europeans used and treated the marine resources. With Native American populations and population density relatively low compared to the numbers once Europeans arrived and eventually settled; “their impact on the marine resources of the vast area of New England and Canadian bays, inlets, and coastal seas was quite small, especially when compared with present practices. Not only were their numbers low, but also they took only what was necessary for the groups to make it through the winter each year” (Pauly & Maclean, 2003, p. 14).
The abundance of marine life in the NW Atlantic prior to European presence seem unfathomable when pictured today. “Snapshots from early navigators, fishers, and biographers, coupled with hard paleo-ecological evidence paint a vastly different portrait of marine life than what can be witnessed today. Turtles in inestimable numbers, an infinite number of them all over the sea; harbors writhing with the silver-sided splashing of striped bass; huge salmon in prodigious quantities; sturgeons in great plenty and so numerous that it is hazardous for canoes; large whale populations which were regularly reported to have hindered the movement of vessels” (Pauly & Maclean, 2003, p. 8). Even allowing for some exaggeration, this portrait is still vastly different from the one that can be seen today.
It is well-documented that as early as the 14th and 15th centuries, European fishermen began seeing the damaging effects on their local Northeast Atlantic fisheries from centuries of overfishing. The once highly abundant halibut and cod populations in those waters began to rapidly shrink in numbers; causing periods of time with substantially lower catch totals. This effect was a major driver behind the boom in the exploration of uncharted lands and waters in the western hemisphere, starting in the late 15th and early 16th century. It should be noted that new fishing grounds were not the sole factor for European exploration (other influences included new trade routes and the search for other natural resources, among other reasons).
In 1497, as navigator John Cabot returned to England from Newfoundland, he gave reports that “alleged the fish were so plentiful that they sometimes stopped the progress of his ships. The exploitation of the rich resource of the sea in the vicinity of Newfoundland began immediately after the return of the earliest journeys of discovery to the northeastern coasts of North America” (Lear, 1998, p. 44). With this information of the New World quickly becoming common knowledge to Europeans; in the 16th century, a race began between various European fishermen, navigators, and settlers (often subsidized by their governments) to lay claim to and begin profiting from this “new” valuable region.
In 1501, the Portuguese began fishing in Newfoundland waters. They were soon followed in large numbers by the French, English, Spanish, and Dutch. The 16th century marks the beginning of the exploitation of marine resources from the overfishing of these waters. As skirmishes and unofficial wars broke out amongst those countries for the most valuable areas, by the late 1500s, the English and French came to hold sway over most of these areas and dominate the fishing industry in the region for the next 200 years. The English and French gained massive profits during this time by controlling the supply of items such as cod, halibut, and whale oil to the Southern European markets.
The late 16th and early 17th centuries saw English and French populations increasing faster than ever before. This coincided with events such as “the growth of the English Navy and its military expeditions, which created a large and continuous demand for food in the form of fish” (Lear, 1998, p. 44). To put this high demand for cod (the most preferred species) into perspective, “by the 17th century, as much as 200,000 metric tons of cod per year (live weight) was leaving Newfoundland for Europe” (Bolster 2008).
Settlements began to spring up throughout the region and the 17th and 18th centuries saw enormous population growth in the New World. Both local and European economies were dominated by the fishing and whaling industry; especially during this period of time. As cod and halibut were being caught in increasing numbers in coastal NW Atlantic waters, whales were starting to see their populations decimated in this region. The whales’ blubber was highly valuable because of its use as a light and heat source. Although large scale whaling operations in these coastal waters started around 1530, the peak of the industry in these particular waters occurred from 1660 to 1701.
That period of time saw “coastal New Englanders and Canadians exploiting local stocks, along with Dutch and Basque whalers in the Western Arctic, harpooning 35,000 to 40,000 whales; depleting populations considerably and affecting the whales’ migration patterns” (Bolster 2008). By 1740, “the pursuit of whales near shore was no longer profitable due to the numbers of those frequenting these coasts very much depleted and which have never since recovered” (Allen, 1928, p. 341). This caused local whalers to have to venture far off-shore, crossing the equator, and eventually into the Pacific to find new, populated whaling grounds.
The region in the mid to late 18th century saw ever-expanding prosperity as a result of its fisheries becoming increasingly exploited. The massive hauls of cod, haddock, hake, pollock, halibut, and herring were critical components in a “three-cornered trade that is often called the Golden Triangle; which sent caught NW Atlantic fish to Europe (receiving the best quality) and the West Indies (receiving the refuse fish) and returned back across the Atlantic with African slaves” (Lear, 1998, p. 53). This highly lucrative operation further raised the demand for these NW Atlantic fisheries’ products, subsequently decreasing local fish populations (particularly cod) in these marine ecosystems.
During the early 19th century, the industry took its first hit due to a large surplus of cod in the market, resulting in large quantities of unsold fish. The consequence of oversupplying the market was felt in the coastal fisheries, which for the first time saw decreased catch totals of cod and halibut along with a decline in quality of those landed fish. During this time, to compensate for those issues, many fishermen ventured to the ice fields in Eastern Canada to profit from the seal fishery. This resulted in the number of seals being harvested rising exponentially. “By 1803, about 53,000 seals had been reported taken. By 1850 to 1860, Newfoundland annual production of seal skins was about 300,000 to 500,000” (Lear, 1998, p. 57).
The late 1800s saw the first significant changes to the region’s fishing industry. In Canada, “a select committee of inquiry heard, in 1862-1863, much evidence of failing cod fisheries, but the Canadian government failed to act on proposed fishery regulations, and instances of conflict followed over the years” (Pauly & Maclean, 2003, p. 15). Local, coastal New England governments also held various town hall meetings, discussing this problem; however, they met the same fate as the previously stated inquiry, and revenue from the industry trumped any significant action. As governmental fishing regulations lay unheard on the back burner, the end of the century saw numerous advancements in fishing equipment. Prior to this time, the most common method used to catch fish in the coastal, inshore fisheries was via hand lines from small boats, and to a degree, gill nets (nets with a small hole that allow only a fish’s head to pass while the fish becomes entrapped at its gills).
The introduction of the first intensive fishing equipment, starting in the 1870s and 1880s, began to replace the traditional methods and allowed for more fish to be caught at a faster pace. This equipment includes innovations such as: the seine net (defined by Merriam-Webster Dictionary as, “large net with sinkers on one edge and floats on the other that hangs vertically in the water and is used to enclose and catch fish when its ends are pulled together or are drawn ashore”); the trap (defined by Lear [1998] as, a “stationary, box-like trap that fish were led into by a leader of netting,” [p. 55], originally designed for cod, the concept was quickly modified to catch other marine species such as lobster); longlines (long fishing lines with hundreds of suspended, baited hooks); and lastly, the trawl-line method (which will be discussed later, but in its early use, it was a fishing method that involved a boat pulling a buoyed fishing line, with many short lines baited with hooks, through the water to catch large quantities of fish).
Along with the equipment innovations during this time, the introduction of steam power, beginning in the later 1860s and early 1870s, led to the use of steamships; which allowed fishermen to safely venture further north through icy winter waters. These areas were previously difficult and dangerous during the winter seasons. It also “enabled larger cargoes of fish to be carries to market than ever before” (Lear, 1998, p. 55).
“Despite the depletion of local cod populations from the mid-1800s, the overall catch increased with the entry (of new equipment and methods) in the late 1800s, rising to over 300,000 metric tons per year.” Lastly, “during the late 1800s, full-time fishers began to diversify and specialize (for example) with lobsters providing a substantial fishery in Maine” (Pauly & Maclean, 2003, p. 15).
Prior to the major technological advancements that started during the second half of the 19th century and continued into the 20th century, the increasing overall catch totals in the NW Atlantic fisheries was mainly resulting from the increase of fishermen and fishing vessels. However, the innovations in technology that started during this period greatly changed that situation and became the main catalyst for overfishing, in an era that saw catch totals increase exponentially, at a pace never before seen throughout its history.
Following World War II, numerous innovations greatly increased the efficiency of fishing fleets; resulting in the onset of industrialized fisheries. While coastal fisheries had started seeing periods of failure due to significant population loss of targeted fish, these new inventions forever changed commercial fishing and possibly, permanently changed marine ecosystems in these waters.
By this time, diesel engines replaced sailing and steam powered ships. Items such as: acoustic fish finders and radar; synthetic netting; midwater otter trawls (defined by Food and Agriculture Organization of the United Nations [FAO] as, “cone-shaped net with a horizontal opening maintained by otter boards to capture fish, and floats and weights providing a vertical opening to hold the fish as the net is towed in midwater” [2015]); bottom trawls (“a large gillnet with heavy weights is dragged across the seafloor, scooping up everything in its path” [Marine Conservation Biology Institute (MCBI), 2005, para. 1]); purse seine nets (defined by Merriam-Webster Dictionary as, “a large seine net designed to be set by two boats around a school of fish and so arranged that after the ends have been brought together, the bottom can be closed”); power blocks (hydraulic winch used to hoist nets onto fishing vessels); improved refrigeration; and huge factory ships with the ability for both catching and processing large quantities of fish (Pauly & Maclean, 2003, p. 18).
These inventions allowed the same number of vessels, with smaller crews, to catch substantially more fish than ever before. They also allowed access to more distant fishing grounds and fish populations, with the ability to stay at sea for even longer durations of time.
During the 1950s and 1960s, coinciding with the implementation of these innovations and expansion of fishing areas, the NW Atlantic fisheries as a whole were highly productive, and “the cod catch, for example, rose to and peaked at 1.7 million metric tons in 1968” (Lear, 1998, p. 67). However, these numbers were highly unsustainable, and cod fisheries in these waters were headed for disaster.
The early 1970s saw the first, partial collapse of all cod fisheries in Eastern Canada. By 1976, the total cod catch in the NW Atlantic fell to 425,000 metric tons. The Canadian government responded with introducing a quota system on total allowable catch limits, and along with the U.S., established the “200 mile limit”. This extended the distance foreign vessels can finish off the coast, from 12 to 200 miles. It proved to be futile because all it did was kick foreign vessels out of these waters and allow domestic vessels to pick up these catch totals. These new policies helped slightly recover catch totals to the 635,000 metric tons mark in the early 1980s. However, “the subsequent policy decisions were driven by flawed and biased scientific advice on the status of cod populations” (Pauly & Maclean, 2003, p. 16).
In 1992, the NW Atlantic suffered the second, and complete collapse of its cod fisheries. Cod catch in the NW Atlantic was the lowest in history, forcing the governments to close the cod fisheries. Canada issued a two year moratorium on cod fishing, but it was too late, and it became extended indefinitely (is still in place today). Currently, there are only a few places in the whole NW Atlantic where cod can be legally fished under tight and ever-changing guidelines.
Unfortunately, even though the once booming and most productive cod fishery in the world has totally collapsed in these waters, overfishing is still a huge problem. “The end of the Cold War made accessible high technologies previously restricted to military applications, for example: precise satellite navigation and positioning; high-resolution maps of the sea bottom; and sensors attached to trawls and other gear” (Pauly & Maclean, 2003, p. 18). Those innovations have “allowed finding and catching any fish concentration, anywhere, including under the ice and in deep, rugged areas and undersea canyons; which were previously impossible to fish and served as natural reserves for exploited species” (Pauly & Maclean, 2003, p. 18).
Along with those advancements, the industry has filled the previous demand for cod by employing the same, unsustainable fishing tactics in landing different fish species. As evidenced through the historical timeline, causes of overfishing in the NW Atlantic come from a variety of areas, such as: the lack of protected areas, the mismanagement of its fisheries (particularly the lack of regulations, enforcement, and incorporation of sound, unbiased scientific advice), and government subsidies creating fishing fleets too large in number. However, by looking at the history of commercial fishing over the past 130 years (particularly from 1950 to present day), it becomes obvious that advancements in technology and fishing equipment have been the greatest contributor to the overfishing problem in the NW Atlantic.
Now that the reader has a solid understanding of what the NW Atlantic looked like before the exploitation of its resources, along with the major historical events that have built up and caused the problem to become what it is today; this paper will now present the impacts that overfishing has had on the marine ecosystems of this region.
Effects
Impacts of Overfishing on Marine Habitat Loss
Marine habitats play a critical role in the health of a functioning ecosystem. Thus, it is important to understand what impacts overfishing has had on these vital marine environments when assessing the overall effects on marine ecosystems. Healthy habitats provide essential shelter, nursery grounds, feeding areas, and refuges for fish and organisms. Marine habitats can be separated into two main groups: coastal and open ocean. Furthermore, these habitats can be divided into two groups describing the depths in where organisms inhabit: pelagic (found towards the surface or in the open water column) and demersal habitats (close to, or on the bottom of the ocean). Specific organisms living in these habitats are often referred to as pelagic or demersal organisms.
Coastal habitats are located from the point where high tide comes into the shoreline of land, and extends to the edge of the continental shelf. Typical coastal habitats in the NW Atlantic include: intertidal zones (areas close to shore which are exposed and submerged by the changing of tides); sandy shores (beaches); rocky shores; mudflats (coastal wetlands formed by rivers or tides depositing mud and other sediments); estuaries (defined by National Oceanic and Atmospheric Administration [NOAA] as, “a partly enclosed body of water where rivers meet the sea, forming a transition zone between fresh and saltwater environments” [2015]); kelp forests; seagrass meadows; and coral reefs.
According to the FAO (n.d., Environmental Role section, para. 3), “coastal habitats (the shelf area) occupy only 7 percent of the total ocean area, however 90 percent of the world’s fish production is dependent on coastal areas at some time in their life cycle; along with supporting large numbers of migratory and non-migratory waterfowl and shorebirds, reptiles, and amphibians. These areas often benefit from flows of nutrients from the land and from ocean upwelling which brings nutrient-rich water to the surface, leading to high biological productivity and rich biodiversity.”
Although these habitat areas comprise such a small number of the total ocean area, they provide the most plentiful sources of nursery and feeding areas for coastal and oceanic aquatic species. This is attributed to: among other things, the abundance of sunlight penetrating the shallow seafloor which allows for high amounts of aquatic vegetation (the base of the food webs); the jagged underwater topography (referred to as bathymetry) creating copious amounts of shelter; and the aforementioned high nutrient levels.
Open ocean habitats are located in the deeper waters beyond the continental shelf. They can be divided into two areas: surface waters and deep sea. As previously stated, the coastal habitats are hot spots for marine life; however, the open ocean is hardly lifeless. Although there are large areas devoid of life in the vast open ocean, there is also very important habitats which are crucial for many species. Particularly, highly migratory species of: fish (i.e. bluefin tuna), marine mammals (i.e. whales and sharks), sea turtles, and seabirds.
The surface waters, referred to as the epipelagic zone, occupy the depth of approximately the first 200 meters of the open ocean. These waters receive enough sunlight to allow photosynthesis; which is mostly performed by microscopic floating algae called phytoplankton. While the epipelagic zone receives enough sunlight to facilitate plant life; in general, this area is low in nutrients due to organic materials sinking to great depths and decomposing far from this zone. This creates areas with little marine life. However, “in some areas, nutrients are brought up from the ocean depths by upwelling, storms, and ocean currents. These areas allow phytoplankton to grow rapidly, in large numbers, creating extremely productive areas capable of supporting billions of tons of life” (World Wildlife Fund [WWF], 2015a). That makes these areas of open ocean, highly critical for those migratory species, whose populations depend on to survive their voyages across the oceans.
While it may seem sparse when compared to the shelter in the coastal waters, the epipelagic zone does offer some shelter to marine life. “Driftwood, pieces of kelp, and other natural debris floating on the water provide valuable shelter where small fish can hide from predators” (WWF, 2015a). In an area of NW Atlantic open ocean where the Gulf Stream converges with the sub-polar gyre and the North Atlantic current, larger areas of floating shelter gather in the surface waters, trapped by the swirling convergence of currents.
Also found in the epipelagic zone of the NW Atlantic are so-called “islands of life.” These are “underwater mountains known as seamounts, which can come within meters of the ocean surface and even break the surface to form islands, which rise steeply from the ocean floor and create great shelter and life opportunities” (WWF, 2015a). Deep-water currents rush up their sides, carrying nutrient-rich water to the surface of these shallow seamounts. These create great conditions for plankton, cold-water corals, sponges, and sea anemones to form dense communities on its rocky slopes. These seamounts are utilized by “some fish species to periodically gather at to feed and spawn, along with marine turtles and whales to stop at for food and shelter during their long migrations” (WWF, 2015a).
The deep sea waters habitat start below the 200 meter mark and extends to the ocean floor, where little sunlight penetrates, causing no photosynthesis to occur. Here, only animals and bacteria who have adapted to the dark and high pressure waters can survive, along with some surface dwellers who can dive to great depths to hunt for food. Currently, little is known regarding life in these deepest and darkest waters. However, we do know that deep sea habitats are varied, including “vast plains, volcanoes, the largest mountain chain on Earth (the Mid-Oceanic Ridge), deep canyons, and sulphurous geysers” (WWF, 2015a).
In the past 30 years, new ecosystems have continued to be discovered in these habitats (i.e. cold-water coral reefs and marine communities living around chemical hot spots emitted from the Earth’s crust). However, only 1 percent of the actual sea floor in the deep sea has been discovered. “Scientists now think there may be more species in the deep sea than in all the other environments on Earth combined” (WWF, 2015a). While these discoveries are exciting, it comes with a feeling of trepidation. As witnessed through the commercial fishing history of the NW Atlantic, as current fisheries continue to be over-exploited and fishing technology continues to advance, it can be deduced that it is only a matter of time before these previously undiscovered and unfished habitats start to be fished in large, unsustainable numbers.
“Habitat alteration by the fishing activities themselves is perhaps the least understood of the important environmental effects of fishing” (National Research Council, Division on Earth and Life Studies, & Ocean Studies Board, 2002, p. 18). Numerous studies conducted over the past 25 years all agree that the single greatest cause of marine habitat loss is from the effects of bottom trawling; however, the full extent of these overall damages is largely unknown, other than from visual assessments of the evidence on the seafloor. The FAO states, “It is difficult to assess the development of bottom trawling on the high seas because reports to the FAO of marine catches make no distinction between where exactly they were landed during high seas bottom trawling. Without reliable data, it is impossible for scientists to provide sound advice, due to the extent of bottom trawling in international waters being poorly known” (as cited in Morgan, Norse, Rogers, Haedrich, & Maxwell, 2005, p. 11).
“The trawl net can stretch to over 40 feet in height and spread over 200 feet wide between the doors, with large, fully rigged nets weighing well over a ton, requiring one or two large powerful boats to drag the net” (MCBI, 2005, para. 2). These trawls are currently capable of fishing depths ranging from 50 to 6,000 feet. The bottom part of the net is held open by heavily weighted ground gear that is designed to drag across the seafloor, and in some cases, is rigged with “tickler chains” which are designed to disturb the seafloor and scare fish from bottom shelter into the net. It is easy to see why this invasive gear is so devastating to marine habitats.
“Habitat damage includes damage to living seafloor structures (i.e. corals, sponges, and sea grasses) as well as alterations to the geologic structures (i.e. boulders, cobbles, gravel, sand, mud) that serve as nursery areas, refuges, and shelters for fish and organisms living in, on, or near the seafloor” (Chuenpagdee, Morgan, Maxwell, Norse, & Pauly, 2003, p. 517). When these bottom trawls are dragged through the ocean, anything in its path is essentially ripped from the ground, flattened, destroyed, and subsequently caught. This includes plants, animals, and structures.
Along with the destruction of habitat structure, bottom trawling also causes the resuspension of toxins and pollutants that have settled into the ocean floor along with “the burying of biologically recyclable organic materials, changing the flow of nutrients through the food web” (as cited in National Research Council et al., 2002, p. 26). When the ocean is encountered with dangerous pollutants, overtime they settle beneath the seafloor and no longer significantly threaten the marine life. However, bottom trawling kicks back up these pollutants, causing its marine life to repeatedly suffer from its damage. These clouds of sediment and toxins are so enormous that they can be seen from satellite imagery in space.
Presently, there are over 30 coral species which have been identified in the NW Atlantic. However, from years of heavy bottom trawling and dredging, most coastal corals in this region have been destroyed; with the majority of remaining species being cold-water coral reefs, such as the predominant Lophelia Pertusa. These struggling populations are mostly found descending the deeper gullies, canyons, and seamounts.
These “reef building corals are very important in the deep sea environment, as they create and modify the surrounding habitat, producing many more places for other animals to live and hide” (Centre for Marine Biodiversity & Biotechnology, n.d.). These extensive coral reef colonies are difficult to replace after they are damaged or destroyed due to their characteristic of being slow-growing and having the longest lifespan on the planet. “Average estimates of growth range from 4 to 25 millimeters per year and are estimated to be over 8,000 years old” (Centre for Marine Biodiversity & Biotechnology, n.d.). By these vital habitat components taking long periods of time to heal or regrow, it leaves the species that rely on them for feeding and spawning grounds, and shelter, to go generations without these critical assets to their lives.
Along with the basic bathymetry and geologic sea floor structures, “aquatic forests,” and coral reef colonies that are destroyed, the other important habitats that are greatly impacted by this invasive gear are the seamounts. Seamounts are important because “they have an exceptionally high proportion of endemic species (species only found in one place and nowhere else). Endemism on seamounts may range as high as 30 to 50 percent, and because there are no sources of recolonization after a seamount is trawled, these areas are especially vulnerable to trawling” (Morgan et al., 2005, p. 10).
Bottom trawling is being witnessed as completely scalping these seamounts bald. “Little is completely known about the role played by coral structures in the life histories of deep sea fish; however, from what is known about corals in shallower regions, it is very likely that this role is substantial, especially during the younger life stages of the fish” (Morgan et al., 2005, p. 11). One can reasonably deduce that these lesser known open ocean habitats that are being destroyed is causing substantial damage to those marine ecosystems.
One can further argue that the open ocean habitat loss is equally feeling the significantly negative effects on its marine ecosystems as those in the more complex, coastal habitats. This is due to the importance of these remote aquatic oases for all the migratory species traveling across the ocean through vast areas of “dead zones.” With much less nutrients and sunlight, along with deeper depths, important habitats are much harder to come by in the open ocean than compared to the coastal waters. This would help explain one factor in why large, migratory species have seen their migratory patterns completely thrown off, along with their stocks decreasing by 90 percent since the 1950s. The inability of these migratory marine species to consistently reach the coastal waters during different seasons is causing problems for coastal ecosystems and their food webs and biodiversity (which will later be discussed in greater detail).
Impacts of Overfishing in Relation to Bycatch
As previously discussed, advancements in commercial fishing gear since 1950 has exponentially increased the efficiency in how fleets catch and harvest seafood. While this has greatly contributed to higher catch totals being brought to the market, it also yields high volumes of bycatch. “Bycatch is the incidental capture of non-target species” (WWF, 2015b). This includes species such as dolphins, whales, sea turtles, birds and among others, “fish that could not be brought to port because they were the wrong size, poor quality, low market value, or prohibited for conservation reasons” (Keledjian et al., 2014, p. 8). Landed catch that is determined as “bycatch,” is subsequently discarded. These discarded species, most of which are dying or dead upon landing, are thrown back into the water. Most scientists estimate that 90 percent of discards do not survive. This causes great harm to marine ecosystems and greatly hinders the ability of threatened species to bounce back.
“Global bycatch may amount to 40 percent of the world’s catch, totaling 63 billion pounds per year. In the U.S. alone, scientists estimate that 17 to 22 percent of U.S. catch, amounting to 2 billion pounds, is discarded every year” (Keledjian et al., 2014, p. 9-10). The most discerning aspect of those statistics is that overall, the severity of the issue is still relatively unknown. This is because, among other reasons, on-board, regulatory monitoring is not present on every vessel and are only accounting for a small percentage of a fleet’s total catch; as well as entire fleets having no monitoring presence at all. Along with insufficient monitoring, the effects of “ghost fishing” are largely unknown. “Due to modern fishing gear being constructed of long-lasting materials, many gear types can continue to function when lost at sea, making it difficult to accurately estimate the impact of ghost fishing on fisheries, since most mortality goes undetected” (Brown, Auster, Lauck, & Coyne, 1998, p. 7).
It should be noted that whenever, and wherever fishing takes place, there will be bycatch. However, these ever-increasing bycatch numbers are mostly the result of modern fishing gear, particularly longlines, trawling, and gillnets, being non-selective in what it catches. Just as some of this gear is destroying marine habitats, it is also having damaging effects on the populations of many different marine species. “Fisheries bycatch has been identified as a primary driver of population declines in several species of marine megafauna due to their interaction with various types of fishing gear because they occupy broad geographic ranges, spanning geopolitical boundaries and oceanographic regions that support many different fisheries” (Wallace et al., 2009, p. 131). To put these population decimations into perspective; globally, “it is estimated that over 300,000 small whales, dolphins, and porpoises (not even including other marine species) die from entanglement in fishing nets each year, making this the single largest cause of mortality for small cetaceans” (WWF, 2015b). Furthermore, statistics from Keledjian et al., (2014) of U.S. fisheries in the NW Atlantic show the following: the coastal bottom trawl, targeting ground-fish, has a discard rate of 35 percent of its total catch; along with the mid-Atlantic bottom trawl targeting scup, flounder, and sea bass having a 33 percent discard rate; Atlantic longline targeting swordfish and tuna having a 23 percent discard rate; and the New England/mid-Atlantic gillnet targeting ground-fish having a 16 percent discard rate.
So how do these population decreases affect the ecosystem as a whole? According to studies conducted by Brown et al. (1998, p. 9), “In the NW Atlantic, 55 percent of stocks of discarded fish species or species groups are having the health of their stock affected from discarding.” The most significant impacts of large bycatch numbers are felt on marine food webs (which will be discussed in greater detail in the following section). For example, when juvenile fish of a “valuable, overfished population” are captured as bycatch and discarded, it diminishes the opportunity for their species’ populations to recover from overfishing. Likewise, when other marine species regularly become bycatch, their populations rapidly decrease and subsequently create “holes” in their local food webs. Along with the impacts on the ecosystem, bycatch and its consequent discarding is also a great waste of oceanic resources. Often times, “target fish for one fishery are discarded as bycatch in a different fishery. For example, if New England trawl fishermen capture summer flounder but lack the permit to keep them, the fish are thrown overboard and wasted, often going undocumented.” Therefore, “discarding large quantities can lead to overfishing, prevent populations from recoveries after decades of overexploitation, and disrupt the natural balance of marine ecosystems” (Keledjian et al., 2014, p. 8).
Impacts of Overfishing on Marine Food Webs and its Biodiversity
The delicate composition of marine food webs are vital to the balance and overall health of marine ecosystems as a whole. “A healthy ecosystem is held together by its food webs” (Northwest Atlantic Marine Alliance [NAMA], 2015). Within a healthy ecosystem, there should exist a high level of biodiversity, which can be seen through the presence of both long and short food webs. Biodiversity is defined as, “the variety within and between all species of plants, animals, and micro-organisms and the ecosystems within which they live and interact” (WWF, 2015a). Therefore, when large numbers of different species’ populations are continually removed from the environment through commercial fishing, and harvested or discarded as bycatch, large gaps start to occupy their food webs.
This greatly alters the structure of the food web and leads to the decline, and eventual extinction, of some species, while simultaneously leading to the overpopulation of other species; thus disturbing the balance of the ecosystem and driving down biodiversity. To show the impacts overfishing is having on NW Atlantic food webs, this research will present the findings as it relates to each trophic level of average, healthy food webs. Trophic levels are defined by Encyclopedia Britannica as, “the steps in a nutritive series, or food web, of an ecosystem, with the organisms of a web classified into these levels on the basis of their feeding behavior” (which can change, as some organisms feed on several trophic levels).
The food webs in the NW Atlantic start at the first trophic level, which consists of the producers, such as tiny plants and algae comprising phytoplankton. This level fluctuates greatly each year and throughout different seasons, as natural, environmentally-driven factors (i.e. weather, sunlight, and oceanic currents) influence its size. This is normal, and in an ecosystem with healthy long and short food webs, the effects of these fluctuations are limited. Also, human factors such as water pollution and excessive nutrient run-off, along with impacts from invasive fishing gear, can have significant effects on the growth of these organisms.
The second trophic level consists of herbivorous (plant eating) consumers, such as zooplankton, krill, and forage fish like mackerel and herring. This is where the effects of overfishing start to significantly show. Due to larger, predatory fish species being the primarily targeted fish for centuries, their populations have decreased dramatically. This had resulted in the industry beginning to target smaller fish, lower in the food web. This has been come to be known as “fishing down the food web.”
Today, “forage fish typically account for more than 30 percent of the total fish caught annually” (Roney, 2013, para. 3). Most of these harvests are used for the extraction of their oil, along with the creation of fishmeal; which in turn, are used in various industries and products such as: fish farming, agriculture feed additive, pet food, fertilizers, and nutritional supplements for humans. Along with the threat of their populations from large catch totals, “forage fish stocks are highly sensitive to environmental change (due to their consumption of susceptible producers) and are prone to population crashes; so fishing levels considered safe in good years can be disastrous in bad ones” (Roney, 2013, para. 2).
The third trophic level consists of first level carnivorous consumers, such as: crustaceans (i.e. crabs, lobsters), juvenile stages of fish, and smaller fish (i.e. haddock, whiting). This is followed by the fourth trophic level, the second level carnivorous consumers, such as cod, saithe, and other predatory fish species. Next, the fifth trophic level, which is comprised of the third level carnivorous consumers, such as squid and seals. This is lastly followed by the sixth trophic level, which are top carnivores, often referred to as “apex predators.” These include species such as: bluefin tuna, shark, dolphin, and albatross.
Trophic levels three through six all share the similarity in which they are all carnivorous consumers; with the differences being in their status as prey for the levels above them, along with the available trophic levels below them in which they feed on. It should be noted that the previous examples of species in trophic levels three through six are subject to change based on the size and composition of the local food web. For example, in shorter, simpler food webs, a trophic level six species such as bluefin tuna may drop down to a level of 3 or 4, based upon length of prey between them and the primary producers.
The first effect of overfishing on these trophic levels is when their populations are decimated from high volumes of larger, mature individuals of these targeted species being caught. The second effect on these trophic levels relates back to bycatch. When juvenile fish of highly targeted species are accidentally caught and discarded, it greatly inhibits the species’ ability to recover to stable numbers. Along with the juvenile targeted species, the non-targeted species that become bycatch face population declines from not only their large bycatch numbers, but also from shortages of food from their prey facing overexploitation.
These overfishing effects have created a trophic cascade in the ecosystems of the NW Atlantic. This is defined as “an ecological phenomenon triggered by the addition or removal of top predators, and involving reciprocal changes in the relative populations of predator and prey through a food web” (Encyclopedia Britannica, n.d.). In some food webs, as upper level, predatory species are eliminated, the lower level prey become released from predation; which results in rising populations of lower level species. However, with the industry increasingly “fishing down the food web,” those released levels are actually now becoming exploited themselves, and are creating massive food shortages for the surviving, upper level species. This results in the large scale shrinking of food webs.
Overall, overfishing in the NW Atlantic has caused severe damage to its food webs, which is continually compromising the health of its marine ecosystems. “Interruptions in these food webs occurring when overfishing changes the balance of species, causing some species to decline or disappear; results in these ecosystems becoming biologically impoverished and less stable” (NAMA, 2015). As previously mentioned, healthy marine ecosystems are comprised of both long and short food webs. In some areas of open ocean, where there is little significant biomass, the simple food webs consist of only a few trophic levels at a given time. Biomass is defined as “the weight at a given time of all the animals and/or plants in a given ecosystem” (Pauly & Maclean, 2003, p. 47). This is in contrast to coastal areas which should often have ecosystems with longer, more complex food webs. To further show how overfishing has negatively impacted marine food webs and biodiversity, one can look at the mean trophic level of landed catch for all the fisheries in the entire NW Atlantic Ocean basin; which shows evidence of “fishing down the food web.”
Figure 1 of the trophic level trends, show an overall rapid decline of mean trophic levels in landings throughout the region since 1950. The sharp increase is explained by Pauly (2010, p. 39) as, “the fisheries were initially dominated by planktivorous menhaden and other, smaller pelagics (aside from cod) at low trophic levels, and as their landings decreased, the average trophic level of the fishery initially increased, then in the 1970s it reversed to a steep decline following increases in the targeting of forage fish.”
“Various studies have shown that such changes in catch composition indicate changes in relative abundance in the underlying ecosystems, and thus reflect the collapse of large populations (when trophic level declines are rapid) or the serial depletion of a number of smaller populations (when declines are gradual, but continuous over longer periods)” (Pauly & Maclean, 2003, p. 50).
This evidence shows that marine food webs in the NW Atlantic are shorter than ever and are overall, lacking the balance with larger food webs. This has driven down the biodiversity of these waters and created massive instability in its ecosystems. “Now in the NW Atlantic; the fishes that fisheries target tend to feed directly on a few species of plankton-feeding fishes, and thus are far more exposed than previously to seasonal and between-year changes of plankton abundance” (Pauly & Maclean, 2003, p. 56). This greatly impacts upper level consumers who are being faced with decreasing food sources. The biggest problem with these unstable ecosystems now consisting of mainly shorter food webs is that their decrease in biodiversity makes them more highly susceptible to succumb to other environmental pressures such as disease, pollution, and climate change; with less of a chance to bounce back and successfully recover.
Socioeconomic Impacts of Overfishing on Humans
While the effects of overfishing in the NW Atlantic are most severely felt on the environment, the impacts also impose negative effects on the social and economic pillars; not only in coastal communities, but for humans worldwide. “Currently, fish provides about 1.5 billion people with 20 percent of their animal protein, and provides another 3 billion people with at least 15 percent of such protein. However, as the demand for seafood increases, so will the price; resulting in billions of people unable to afford seafood due to increasing demand in wealthy nations, and vast commercial fleets that will out-compete local subsistence fishermen” (Jones, 2013, p. 2).
Along with other populations around the globe, seafood has long been a staple in meals for regional and coastal communities along the NW Atlantic coast. The past few hundred years have seen the cooking and consumption of seafood dishes grow into a tradition for these families. As the prices become unaffordable and the resources continue to diminish, a growing number of families will be forced to end these long-standing traditions and look for other options to fill this cultural void. Unfortunately, this end could be coming sooner than most think. “Overfishing is a time-sensitive issue, and if not addressed immediately, researchers and ecologists fear that the world could run out of seafood by 2048” (Jones, 2013, p. 3).
Not only does this directly impact the actual human consumption of seafood, but this will affect other products that consumers purchase. Sea products are now used by humans in a variety of ways, being an input in items such as: cosmetic products (i.e. make-ups and body washes); medical products (i.e. creams, nutritional supplements, and skin treatments); fertilizers; pet foods; and many other manufactured products. While prices for such items have already seen increases, the loss of a valuable input could threaten those industries as well.
Lastly, the loss of jobs in the commercial fishing industry has greatly impacted families in New England and Eastern Canada. In one example, “closures of the Canadian cod fisheries meant that by 1995, some 40,000 fishers and shore workers had been displaced, disrupting many coastal communities” (Pauly & Maclean, 2003, p. 16). This is particularly unfortunate because, although the local, inshore fishermen had long called for a bigger share of catch quotas, it was generally in response to the large, corporate fleets making their landings unprofitable and forcing them out of the market.
“The structure of the local, inshore fishery and the methods that were used in it meant that these fishermen did not have the capacity to greatly overfish the resource. They used fixed gear and small nets that could usually be manipulated by hand or with little mechanical assistance, never leading to anywhere near as high a catch as those taken by the corporate sector. As well, the crews tended to be composed of household and family members, and were usually not interested in running their operation as a business venture whose sole goal was the generation of profit. It was almost like a subsistence economy for many” (Mason, 2002, p. 3).
With the area continuing to be overfished, the overexploited stocks not recovering to commercial viability (or even environmental viability), and large corporate fleets with high-tech equipment and small crews dominating the inshore and offshore operations; most of the unemployed fishermen were forced to find new work outside the industry. Thus breaking years, and in some cases, centuries, of family tradition working in the fishing industry. In many places, such as Newfoundland, Labrador, coastal Maine, and Massachusetts, many of the displaced workers and their families have suffered greatly from a lack of work. This is because jobs are scarce in these places, where fishing had been the main economic industry for hundreds of years.
Conclusion
In conclusion, overfishing has negatively affected every aspect of marine ecosystems in the NW Atlantic. It has caused the large-scale destruction and loss of marine habitats; decimated populations of non-targeted species and unconsumed targeted species (wasting valuable resources); shortened food webs; extirpated species; and significantly decreased overall biodiversity. In turn, this has decreased the overall health of these ecosystems; making them fragile, unstable, and highly susceptible to other environmental and human-influenced factors.
While some may argue that the decline of marine ecosystems in the NW Atlantic (and globally) is attributed to these other factors; there is no denying the historical buildup of evidence that suggests overfishing as having the most damaging effects on marine ecosystems. “While it is often overlooked for other environmental issues, overfishing has historically caused more ecological extinction than any other human influence on coastal ecosystems, including water pollution. Unfortunately, due to a lack of data, the extent of this damage has only recently been recognized” (Dartmouth Undergraduate Journal of Science, 2012, para. 11).
Many species from these waters are gone forever, and many remaining species are overexploited to the point where their recovery is debated and largely unknown. While overfishing has greatly altered the ecological composition of these waters from the days of pre-European arrival; it is unknown whether these ecosystems can even rebound enough to hold healthy, sustainable, and biologically diverse populations of plant and animal species. However, one thing is certain amongst most scientists; if current practice is not quickly and drastically changed to more sustainable fishing and management methods, these important marine ecosystems and valuable resources will be lost forever.
As that time quickly approaches, humans will also continue to feel the increasing social and economic ramifications of this problem. As John Muir, the renowned environmentalist and founder of the Sierra Club once stated, “When we try to pick out anything by itself, we find it hitched to everything else in the universe” (as cited in Sierra Club, n.d.).
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What are the Effects of Overfishing on Marine Ecosystems in the Northwest Atlantic Ocean?
Christopher D. Lampart
Community College of Vermont - Winooski
Abstract
This paper explores the negative effects that overfishing has had on marine ecosystems in the Northwest Atlantic Ocean. Overfishing is defined as “fishing with a sufficiently high intensity to reduce the breeding stock levels to such an extent that they will no longer support a sufficient quantity of fish for sport or commercial harvest” (as cited in Koster, What is Overfishing section, para. 5). The paper will provide a detailed history of overfishing in this region which will identify the causes of this problem. There will be a focus on the effects overfishing plays on marine habitat loss, bycatch, and marine food webs and biodiversity. Along with the environmental effects, the study will also examine the socioeconomic effects on humans, to help educate and bring relevant awareness to all people throughout New England, Eastern Canada and worldwide. The research gathered for this is drawn from government agencies, scientific papers, non-profit organizations, and previous studies; and will be analyzed through an ecosystem perspective. The goal of this study is to lay out the current impacts overfishing has on marine ecosystems so that new and improved solutions can be created and implemented in the near future; utilizing this research as its foundation. It should be noted that, for this paper, aside from mentioning specific fish species; fish will be described as to mean, “all organisms targeted and fished, all animals caught by humans, including fish, shellfish, and mollusks” (Pauly & Maclean, 2003, p. 4).
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Panic in the North Atlantic
What are the Effects of Overfishing on Marine Ecosystems in the Northwest Atlantic Ocean?
As it stands today, the global community faces a major problem with its oceanic ecosystems and fisheries (fishery is defined by Encyclopedia Britannica as, “the activity of harvesting fish, shellfish, and marine mammals as a commercial enterprise, or the location or season of commercial fishing”) in regards to the state of commercial fishing. The effects of overfishing are not only being felt by ocean-front populations; instead, international communities (including places like landlocked Vermont) of animals, plants, and humans are facing the consequences associated with this issue. Unfortunately, most humans are not aware of this problem and the scope of its impacts. Thanks to the high, readily available access to seafood and sea products, along with the glamorization of commercial fishing from Hollywood and television shows such as The Deadliest Catch and Wicked Tuna, it’s easy to see why the majority of the population has no idea of the crisis the planet is facing.
The question then arises, what are the effects of overfishing on marine ecosystems, specifically in the Northwest Atlantic Ocean? In order to thoroughly answer that question, this research will first examine and present in great detail the history of NW Atlantic commercial fishing, as well as identify the causes of overfishing in the region. Due to the complexity of the overfishing problem, this research will not examine the impacts on only one particular species, but instead will focus on marine ecosystems as a whole; presenting the effects through the lens of an interacting ecosystem (the ecosystem perspective). While this research will look at this problem from the ecosystem perspective, it is important to note that the codfish species will be discussed often throughout this research due to its high significance in this region and its role as the preferred global fish species of consumption for hundreds of years.
The following questions must then be analyzed and answered: What are the impacts of overfishing on marine habitats, what are the impacts in relation to bycatch, and what are the impacts on marine food webs and its role in biodiversity? While the environment suffers greatest from the negative effects; issues trickle down into humans’ social and economic realms, which further complicate the problem. Therefore, it must also be determined what the socioeconomic effects on humans are.
History and Causes of Overfishing
In order to fully understand the effects that overfishing has had on marine ecosystems in the NW Atlantic Ocean, one must first comprehend and visualize what this oceanic area looked like prior to its exploitation, along with the historical timeline of events that have contributed to the demise of these ecosystems. The physical, geologic make-up of the NW Atlantic sets the stage for these once lush marine ecosystems, filled with large populations of diverse animals and plant species.
Two significant, physical features helped contribute to the success of these ecosystems. The first, is the Mid-Atlantic Ridge, which is “an immense median mountain range extending throughout the length of the Atlantic, claiming the center third of the ocean bed” (Encyclopedia Britannica). This feature provides excellent life opportunities for species in the middle of the ocean. Greatly benefitting migratory species who utilize these areas as feeding grounds during their long voyage to and from the NW Atlantic.
The second notable feature is the continental shelf along the eastern seaboard of North America (particularly the coastlines of New England and Eastern Canada). “Continental shelves were formed in between glacial periods as the ocean flowed over the continents forming shallow areas along the coasts. They are an oasis in the ocean for plants and animals due to the abundance of sunlight, shallow waters, and nutrient packed sediment that washes in from rivers and wave action. The continental shelf in the NW Atlantic has provided 90 percent of the fisheries production in the region” (MarineBio Conservation Society, n.d.).
The exploitation of fisheries in this region begins at the time of Europeans arriving in the “New World.” For centuries prior to the Europeans’ arrival, coastal Native American tribes such as the Inuit, Mi’kmaq, Wampanoag, and Narragansett (among others), were the only people utilizing these fisheries. However, there is a stark contrast between the way the Natives and Europeans used and treated the marine resources. With Native American populations and population density relatively low compared to the numbers once Europeans arrived and eventually settled; “their impact on the marine resources of the vast area of New England and Canadian bays, inlets, and coastal seas was quite small, especially when compared with present practices. Not only were their numbers low, but also they took only what was necessary for the groups to make it through the winter each year” (Pauly & Maclean, 2003, p. 14).
The abundance of marine life in the NW Atlantic prior to European presence seem unfathomable when pictured today. “Snapshots from early navigators, fishers, and biographers, coupled with hard paleo-ecological evidence paint a vastly different portrait of marine life than what can be witnessed today. Turtles in inestimable numbers, an infinite number of them all over the sea; harbors writhing with the silver-sided splashing of striped bass; huge salmon in prodigious quantities; sturgeons in great plenty and so numerous that it is hazardous for canoes; large whale populations which were regularly reported to have hindered the movement of vessels” (Pauly & Maclean, 2003, p. 8). Even allowing for some exaggeration, this portrait is still vastly different from the one that can be seen today.
It is well-documented that as early as the 14th and 15th centuries, European fishermen began seeing the damaging effects on their local Northeast Atlantic fisheries from centuries of overfishing. The once highly abundant halibut and cod populations in those waters began to rapidly shrink in numbers; causing periods of time with substantially lower catch totals. This effect was a major driver behind the boom in the exploration of uncharted lands and waters in the western hemisphere, starting in the late 15th and early 16th century. It should be noted that new fishing grounds were not the sole factor for European exploration (other influences included new trade routes and the search for other natural resources, among other reasons).
In 1497, as navigator John Cabot returned to England from Newfoundland, he gave reports that “alleged the fish were so plentiful that they sometimes stopped the progress of his ships. The exploitation of the rich resource of the sea in the vicinity of Newfoundland began immediately after the return of the earliest journeys of discovery to the northeastern coasts of North America” (Lear, 1998, p. 44). With this information of the New World quickly becoming common knowledge to Europeans; in the 16th century, a race began between various European fishermen, navigators, and settlers (often subsidized by their governments) to lay claim to and begin profiting from this “new” valuable region.
In 1501, the Portuguese began fishing in Newfoundland waters. They were soon followed in large numbers by the French, English, Spanish, and Dutch. The 16th century marks the beginning of the exploitation of marine resources from the overfishing of these waters. As skirmishes and unofficial wars broke out amongst those countries for the most valuable areas, by the late 1500s, the English and French came to hold sway over most of these areas and dominate the fishing industry in the region for the next 200 years. The English and French gained massive profits during this time by controlling the supply of items such as cod, halibut, and whale oil to the Southern European markets.
The late 16th and early 17th centuries saw English and French populations increasing faster than ever before. This coincided with events such as “the growth of the English Navy and its military expeditions, which created a large and continuous demand for food in the form of fish” (Lear, 1998, p. 44). To put this high demand for cod (the most preferred species) into perspective, “by the 17th century, as much as 200,000 metric tons of cod per year (live weight) was leaving Newfoundland for Europe” (Bolster 2008).
Settlements began to spring up throughout the region and the 17th and 18th centuries saw enormous population growth in the New World. Both local and European economies were dominated by the fishing and whaling industry; especially during this period of time. As cod and halibut were being caught in increasing numbers in coastal NW Atlantic waters, whales were starting to see their populations decimated in this region. The whales’ blubber was highly valuable because of its use as a light and heat source. Although large scale whaling operations in these coastal waters started around 1530, the peak of the industry in these particular waters occurred from 1660 to 1701.
That period of time saw “coastal New Englanders and Canadians exploiting local stocks, along with Dutch and Basque whalers in the Western Arctic, harpooning 35,000 to 40,000 whales; depleting populations considerably and affecting the whales’ migration patterns” (Bolster 2008). By 1740, “the pursuit of whales near shore was no longer profitable due to the numbers of those frequenting these coasts very much depleted and which have never since recovered” (Allen, 1928, p. 341). This caused local whalers to have to venture far off-shore, crossing the equator, and eventually into the Pacific to find new, populated whaling grounds.
The region in the mid to late 18th century saw ever-expanding prosperity as a result of its fisheries becoming increasingly exploited. The massive hauls of cod, haddock, hake, pollock, halibut, and herring were critical components in a “three-cornered trade that is often called the Golden Triangle; which sent caught NW Atlantic fish to Europe (receiving the best quality) and the West Indies (receiving the refuse fish) and returned back across the Atlantic with African slaves” (Lear, 1998, p. 53). This highly lucrative operation further raised the demand for these NW Atlantic fisheries’ products, subsequently decreasing local fish populations (particularly cod) in these marine ecosystems.
During the early 19th century, the industry took its first hit due to a large surplus of cod in the market, resulting in large quantities of unsold fish. The consequence of oversupplying the market was felt in the coastal fisheries, which for the first time saw decreased catch totals of cod and halibut along with a decline in quality of those landed fish. During this time, to compensate for those issues, many fishermen ventured to the ice fields in Eastern Canada to profit from the seal fishery. This resulted in the number of seals being harvested rising exponentially. “By 1803, about 53,000 seals had been reported taken. By 1850 to 1860, Newfoundland annual production of seal skins was about 300,000 to 500,000” (Lear, 1998, p. 57).
The late 1800s saw the first significant changes to the region’s fishing industry. In Canada, “a select committee of inquiry heard, in 1862-1863, much evidence of failing cod fisheries, but the Canadian government failed to act on proposed fishery regulations, and instances of conflict followed over the years” (Pauly & Maclean, 2003, p. 15). Local, coastal New England governments also held various town hall meetings, discussing this problem; however, they met the same fate as the previously stated inquiry, and revenue from the industry trumped any significant action. As governmental fishing regulations lay unheard on the back burner, the end of the century saw numerous advancements in fishing equipment. Prior to this time, the most common method used to catch fish in the coastal, inshore fisheries was via hand lines from small boats, and to a degree, gill nets (nets with a small hole that allow only a fish’s head to pass while the fish becomes entrapped at its gills).
The introduction of the first intensive fishing equipment, starting in the 1870s and 1880s, began to replace the traditional methods and allowed for more fish to be caught at a faster pace. This equipment includes innovations such as: the seine net (defined by Merriam-Webster Dictionary as, “large net with sinkers on one edge and floats on the other that hangs vertically in the water and is used to enclose and catch fish when its ends are pulled together or are drawn ashore”); the trap (defined by Lear [1998] as, a “stationary, box-like trap that fish were led into by a leader of netting,” [p. 55], originally designed for cod, the concept was quickly modified to catch other marine species such as lobster); longlines (long fishing lines with hundreds of suspended, baited hooks); and lastly, the trawl-line method (which will be discussed later, but in its early use, it was a fishing method that involved a boat pulling a buoyed fishing line, with many short lines baited with hooks, through the water to catch large quantities of fish).
Along with the equipment innovations during this time, the introduction of steam power, beginning in the later 1860s and early 1870s, led to the use of steamships; which allowed fishermen to safely venture further north through icy winter waters. These areas were previously difficult and dangerous during the winter seasons. It also “enabled larger cargoes of fish to be carries to market than ever before” (Lear, 1998, p. 55).
“Despite the depletion of local cod populations from the mid-1800s, the overall catch increased with the entry (of new equipment and methods) in the late 1800s, rising to over 300,000 metric tons per year.” Lastly, “during the late 1800s, full-time fishers began to diversify and specialize (for example) with lobsters providing a substantial fishery in Maine” (Pauly & Maclean, 2003, p. 15).
Prior to the major technological advancements that started during the second half of the 19th century and continued into the 20th century, the increasing overall catch totals in the NW Atlantic fisheries was mainly resulting from the increase of fishermen and fishing vessels. However, the innovations in technology that started during this period greatly changed that situation and became the main catalyst for overfishing, in an era that saw catch totals increase exponentially, at a pace never before seen throughout its history.
Following World War II, numerous innovations greatly increased the efficiency of fishing fleets; resulting in the onset of industrialized fisheries. While coastal fisheries had started seeing periods of failure due to significant population loss of targeted fish, these new inventions forever changed commercial fishing and possibly, permanently changed marine ecosystems in these waters.
By this time, diesel engines replaced sailing and steam powered ships. Items such as: acoustic fish finders and radar; synthetic netting; midwater otter trawls (defined by Food and Agriculture Organization of the United Nations [FAO] as, “cone-shaped net with a horizontal opening maintained by otter boards to capture fish, and floats and weights providing a vertical opening to hold the fish as the net is towed in midwater” [2015]); bottom trawls (“a large gillnet with heavy weights is dragged across the seafloor, scooping up everything in its path” [Marine Conservation Biology Institute (MCBI), 2005, para. 1]); purse seine nets (defined by Merriam-Webster Dictionary as, “a large seine net designed to be set by two boats around a school of fish and so arranged that after the ends have been brought together, the bottom can be closed”); power blocks (hydraulic winch used to hoist nets onto fishing vessels); improved refrigeration; and huge factory ships with the ability for both catching and processing large quantities of fish (Pauly & Maclean, 2003, p. 18).
These inventions allowed the same number of vessels, with smaller crews, to catch substantially more fish than ever before. They also allowed access to more distant fishing grounds and fish populations, with the ability to stay at sea for even longer durations of time.
During the 1950s and 1960s, coinciding with the implementation of these innovations and expansion of fishing areas, the NW Atlantic fisheries as a whole were highly productive, and “the cod catch, for example, rose to and peaked at 1.7 million metric tons in 1968” (Lear, 1998, p. 67). However, these numbers were highly unsustainable, and cod fisheries in these waters were headed for disaster.
The early 1970s saw the first, partial collapse of all cod fisheries in Eastern Canada. By 1976, the total cod catch in the NW Atlantic fell to 425,000 metric tons. The Canadian government responded with introducing a quota system on total allowable catch limits, and along with the U.S., established the “200 mile limit”. This extended the distance foreign vessels can finish off the coast, from 12 to 200 miles. It proved to be futile because all it did was kick foreign vessels out of these waters and allow domestic vessels to pick up these catch totals. These new policies helped slightly recover catch totals to the 635,000 metric tons mark in the early 1980s. However, “the subsequent policy decisions were driven by flawed and biased scientific advice on the status of cod populations” (Pauly & Maclean, 2003, p. 16).
In 1992, the NW Atlantic suffered the second, and complete collapse of its cod fisheries. Cod catch in the NW Atlantic was the lowest in history, forcing the governments to close the cod fisheries. Canada issued a two year moratorium on cod fishing, but it was too late, and it became extended indefinitely (is still in place today). Currently, there are only a few places in the whole NW Atlantic where cod can be legally fished under tight and ever-changing guidelines.
Unfortunately, even though the once booming and most productive cod fishery in the world has totally collapsed in these waters, overfishing is still a huge problem. “The end of the Cold War made accessible high technologies previously restricted to military applications, for example: precise satellite navigation and positioning; high-resolution maps of the sea bottom; and sensors attached to trawls and other gear” (Pauly & Maclean, 2003, p. 18). Those innovations have “allowed finding and catching any fish concentration, anywhere, including under the ice and in deep, rugged areas and undersea canyons; which were previously impossible to fish and served as natural reserves for exploited species” (Pauly & Maclean, 2003, p. 18).
Along with those advancements, the industry has filled the previous demand for cod by employing the same, unsustainable fishing tactics in landing different fish species. As evidenced through the historical timeline, causes of overfishing in the NW Atlantic come from a variety of areas, such as: the lack of protected areas, the mismanagement of its fisheries (particularly the lack of regulations, enforcement, and incorporation of sound, unbiased scientific advice), and government subsidies creating fishing fleets too large in number. However, by looking at the history of commercial fishing over the past 130 years (particularly from 1950 to present day), it becomes obvious that advancements in technology and fishing equipment have been the greatest contributor to the overfishing problem in the NW Atlantic.
Now that the reader has a solid understanding of what the NW Atlantic looked like before the exploitation of its resources, along with the major historical events that have built up and caused the problem to become what it is today; this paper will now present the impacts that overfishing has had on the marine ecosystems of this region.
Effects
Impacts of Overfishing on Marine Habitat Loss
Marine habitats play a critical role in the health of a functioning ecosystem. Thus, it is important to understand what impacts overfishing has had on these vital marine environments when assessing the overall effects on marine ecosystems. Healthy habitats provide essential shelter, nursery grounds, feeding areas, and refuges for fish and organisms. Marine habitats can be separated into two main groups: coastal and open ocean. Furthermore, these habitats can be divided into two groups describing the depths in where organisms inhabit: pelagic (found towards the surface or in the open water column) and demersal habitats (close to, or on the bottom of the ocean). Specific organisms living in these habitats are often referred to as pelagic or demersal organisms.
Coastal habitats are located from the point where high tide comes into the shoreline of land, and extends to the edge of the continental shelf. Typical coastal habitats in the NW Atlantic include: intertidal zones (areas close to shore which are exposed and submerged by the changing of tides); sandy shores (beaches); rocky shores; mudflats (coastal wetlands formed by rivers or tides depositing mud and other sediments); estuaries (defined by National Oceanic and Atmospheric Administration [NOAA] as, “a partly enclosed body of water where rivers meet the sea, forming a transition zone between fresh and saltwater environments” [2015]); kelp forests; seagrass meadows; and coral reefs.
According to the FAO (n.d., Environmental Role section, para. 3), “coastal habitats (the shelf area) occupy only 7 percent of the total ocean area, however 90 percent of the world’s fish production is dependent on coastal areas at some time in their life cycle; along with supporting large numbers of migratory and non-migratory waterfowl and shorebirds, reptiles, and amphibians. These areas often benefit from flows of nutrients from the land and from ocean upwelling which brings nutrient-rich water to the surface, leading to high biological productivity and rich biodiversity.”
Although these habitat areas comprise such a small number of the total ocean area, they provide the most plentiful sources of nursery and feeding areas for coastal and oceanic aquatic species. This is attributed to: among other things, the abundance of sunlight penetrating the shallow seafloor which allows for high amounts of aquatic vegetation (the base of the food webs); the jagged underwater topography (referred to as bathymetry) creating copious amounts of shelter; and the aforementioned high nutrient levels.
Open ocean habitats are located in the deeper waters beyond the continental shelf. They can be divided into two areas: surface waters and deep sea. As previously stated, the coastal habitats are hot spots for marine life; however, the open ocean is hardly lifeless. Although there are large areas devoid of life in the vast open ocean, there is also very important habitats which are crucial for many species. Particularly, highly migratory species of: fish (i.e. bluefin tuna), marine mammals (i.e. whales and sharks), sea turtles, and seabirds.
The surface waters, referred to as the epipelagic zone, occupy the depth of approximately the first 200 meters of the open ocean. These waters receive enough sunlight to allow photosynthesis; which is mostly performed by microscopic floating algae called phytoplankton. While the epipelagic zone receives enough sunlight to facilitate plant life; in general, this area is low in nutrients due to organic materials sinking to great depths and decomposing far from this zone. This creates areas with little marine life. However, “in some areas, nutrients are brought up from the ocean depths by upwelling, storms, and ocean currents. These areas allow phytoplankton to grow rapidly, in large numbers, creating extremely productive areas capable of supporting billions of tons of life” (World Wildlife Fund [WWF], 2015a). That makes these areas of open ocean, highly critical for those migratory species, whose populations depend on to survive their voyages across the oceans.
While it may seem sparse when compared to the shelter in the coastal waters, the epipelagic zone does offer some shelter to marine life. “Driftwood, pieces of kelp, and other natural debris floating on the water provide valuable shelter where small fish can hide from predators” (WWF, 2015a). In an area of NW Atlantic open ocean where the Gulf Stream converges with the sub-polar gyre and the North Atlantic current, larger areas of floating shelter gather in the surface waters, trapped by the swirling convergence of currents.
Also found in the epipelagic zone of the NW Atlantic are so-called “islands of life.” These are “underwater mountains known as seamounts, which can come within meters of the ocean surface and even break the surface to form islands, which rise steeply from the ocean floor and create great shelter and life opportunities” (WWF, 2015a). Deep-water currents rush up their sides, carrying nutrient-rich water to the surface of these shallow seamounts. These create great conditions for plankton, cold-water corals, sponges, and sea anemones to form dense communities on its rocky slopes. These seamounts are utilized by “some fish species to periodically gather at to feed and spawn, along with marine turtles and whales to stop at for food and shelter during their long migrations” (WWF, 2015a).
The deep sea waters habitat start below the 200 meter mark and extends to the ocean floor, where little sunlight penetrates, causing no photosynthesis to occur. Here, only animals and bacteria who have adapted to the dark and high pressure waters can survive, along with some surface dwellers who can dive to great depths to hunt for food. Currently, little is known regarding life in these deepest and darkest waters. However, we do know that deep sea habitats are varied, including “vast plains, volcanoes, the largest mountain chain on Earth (the Mid-Oceanic Ridge), deep canyons, and sulphurous geysers” (WWF, 2015a).
In the past 30 years, new ecosystems have continued to be discovered in these habitats (i.e. cold-water coral reefs and marine communities living around chemical hot spots emitted from the Earth’s crust). However, only 1 percent of the actual sea floor in the deep sea has been discovered. “Scientists now think there may be more species in the deep sea than in all the other environments on Earth combined” (WWF, 2015a). While these discoveries are exciting, it comes with a feeling of trepidation. As witnessed through the commercial fishing history of the NW Atlantic, as current fisheries continue to be over-exploited and fishing technology continues to advance, it can be deduced that it is only a matter of time before these previously undiscovered and unfished habitats start to be fished in large, unsustainable numbers.
“Habitat alteration by the fishing activities themselves is perhaps the least understood of the important environmental effects of fishing” (National Research Council, Division on Earth and Life Studies, & Ocean Studies Board, 2002, p. 18). Numerous studies conducted over the past 25 years all agree that the single greatest cause of marine habitat loss is from the effects of bottom trawling; however, the full extent of these overall damages is largely unknown, other than from visual assessments of the evidence on the seafloor. The FAO states, “It is difficult to assess the development of bottom trawling on the high seas because reports to the FAO of marine catches make no distinction between where exactly they were landed during high seas bottom trawling. Without reliable data, it is impossible for scientists to provide sound advice, due to the extent of bottom trawling in international waters being poorly known” (as cited in Morgan, Norse, Rogers, Haedrich, & Maxwell, 2005, p. 11).
“The trawl net can stretch to over 40 feet in height and spread over 200 feet wide between the doors, with large, fully rigged nets weighing well over a ton, requiring one or two large powerful boats to drag the net” (MCBI, 2005, para. 2). These trawls are currently capable of fishing depths ranging from 50 to 6,000 feet. The bottom part of the net is held open by heavily weighted ground gear that is designed to drag across the seafloor, and in some cases, is rigged with “tickler chains” which are designed to disturb the seafloor and scare fish from bottom shelter into the net. It is easy to see why this invasive gear is so devastating to marine habitats.
“Habitat damage includes damage to living seafloor structures (i.e. corals, sponges, and sea grasses) as well as alterations to the geologic structures (i.e. boulders, cobbles, gravel, sand, mud) that serve as nursery areas, refuges, and shelters for fish and organisms living in, on, or near the seafloor” (Chuenpagdee, Morgan, Maxwell, Norse, & Pauly, 2003, p. 517). When these bottom trawls are dragged through the ocean, anything in its path is essentially ripped from the ground, flattened, destroyed, and subsequently caught. This includes plants, animals, and structures.
Along with the destruction of habitat structure, bottom trawling also causes the resuspension of toxins and pollutants that have settled into the ocean floor along with “the burying of biologically recyclable organic materials, changing the flow of nutrients through the food web” (as cited in National Research Council et al., 2002, p. 26). When the ocean is encountered with dangerous pollutants, overtime they settle beneath the seafloor and no longer significantly threaten the marine life. However, bottom trawling kicks back up these pollutants, causing its marine life to repeatedly suffer from its damage. These clouds of sediment and toxins are so enormous that they can be seen from satellite imagery in space.
Presently, there are over 30 coral species which have been identified in the NW Atlantic. However, from years of heavy bottom trawling and dredging, most coastal corals in this region have been destroyed; with the majority of remaining species being cold-water coral reefs, such as the predominant Lophelia Pertusa. These struggling populations are mostly found descending the deeper gullies, canyons, and seamounts.
These “reef building corals are very important in the deep sea environment, as they create and modify the surrounding habitat, producing many more places for other animals to live and hide” (Centre for Marine Biodiversity & Biotechnology, n.d.). These extensive coral reef colonies are difficult to replace after they are damaged or destroyed due to their characteristic of being slow-growing and having the longest lifespan on the planet. “Average estimates of growth range from 4 to 25 millimeters per year and are estimated to be over 8,000 years old” (Centre for Marine Biodiversity & Biotechnology, n.d.). By these vital habitat components taking long periods of time to heal or regrow, it leaves the species that rely on them for feeding and spawning grounds, and shelter, to go generations without these critical assets to their lives.
Along with the basic bathymetry and geologic sea floor structures, “aquatic forests,” and coral reef colonies that are destroyed, the other important habitats that are greatly impacted by this invasive gear are the seamounts. Seamounts are important because “they have an exceptionally high proportion of endemic species (species only found in one place and nowhere else). Endemism on seamounts may range as high as 30 to 50 percent, and because there are no sources of recolonization after a seamount is trawled, these areas are especially vulnerable to trawling” (Morgan et al., 2005, p. 10).
Bottom trawling is being witnessed as completely scalping these seamounts bald. “Little is completely known about the role played by coral structures in the life histories of deep sea fish; however, from what is known about corals in shallower regions, it is very likely that this role is substantial, especially during the younger life stages of the fish” (Morgan et al., 2005, p. 11). One can reasonably deduce that these lesser known open ocean habitats that are being destroyed is causing substantial damage to those marine ecosystems.
One can further argue that the open ocean habitat loss is equally feeling the significantly negative effects on its marine ecosystems as those in the more complex, coastal habitats. This is due to the importance of these remote aquatic oases for all the migratory species traveling across the ocean through vast areas of “dead zones.” With much less nutrients and sunlight, along with deeper depths, important habitats are much harder to come by in the open ocean than compared to the coastal waters. This would help explain one factor in why large, migratory species have seen their migratory patterns completely thrown off, along with their stocks decreasing by 90 percent since the 1950s. The inability of these migratory marine species to consistently reach the coastal waters during different seasons is causing problems for coastal ecosystems and their food webs and biodiversity (which will later be discussed in greater detail).
Impacts of Overfishing in Relation to Bycatch
As previously discussed, advancements in commercial fishing gear since 1950 has exponentially increased the efficiency in how fleets catch and harvest seafood. While this has greatly contributed to higher catch totals being brought to the market, it also yields high volumes of bycatch. “Bycatch is the incidental capture of non-target species” (WWF, 2015b). This includes species such as dolphins, whales, sea turtles, birds and among others, “fish that could not be brought to port because they were the wrong size, poor quality, low market value, or prohibited for conservation reasons” (Keledjian et al., 2014, p. 8). Landed catch that is determined as “bycatch,” is subsequently discarded. These discarded species, most of which are dying or dead upon landing, are thrown back into the water. Most scientists estimate that 90 percent of discards do not survive. This causes great harm to marine ecosystems and greatly hinders the ability of threatened species to bounce back.
“Global bycatch may amount to 40 percent of the world’s catch, totaling 63 billion pounds per year. In the U.S. alone, scientists estimate that 17 to 22 percent of U.S. catch, amounting to 2 billion pounds, is discarded every year” (Keledjian et al., 2014, p. 9-10). The most discerning aspect of those statistics is that overall, the severity of the issue is still relatively unknown. This is because, among other reasons, on-board, regulatory monitoring is not present on every vessel and are only accounting for a small percentage of a fleet’s total catch; as well as entire fleets having no monitoring presence at all. Along with insufficient monitoring, the effects of “ghost fishing” are largely unknown. “Due to modern fishing gear being constructed of long-lasting materials, many gear types can continue to function when lost at sea, making it difficult to accurately estimate the impact of ghost fishing on fisheries, since most mortality goes undetected” (Brown, Auster, Lauck, & Coyne, 1998, p. 7).
It should be noted that whenever, and wherever fishing takes place, there will be bycatch. However, these ever-increasing bycatch numbers are mostly the result of modern fishing gear, particularly longlines, trawling, and gillnets, being non-selective in what it catches. Just as some of this gear is destroying marine habitats, it is also having damaging effects on the populations of many different marine species. “Fisheries bycatch has been identified as a primary driver of population declines in several species of marine megafauna due to their interaction with various types of fishing gear because they occupy broad geographic ranges, spanning geopolitical boundaries and oceanographic regions that support many different fisheries” (Wallace et al., 2009, p. 131). To put these population decimations into perspective; globally, “it is estimated that over 300,000 small whales, dolphins, and porpoises (not even including other marine species) die from entanglement in fishing nets each year, making this the single largest cause of mortality for small cetaceans” (WWF, 2015b). Furthermore, statistics from Keledjian et al., (2014) of U.S. fisheries in the NW Atlantic show the following: the coastal bottom trawl, targeting ground-fish, has a discard rate of 35 percent of its total catch; along with the mid-Atlantic bottom trawl targeting scup, flounder, and sea bass having a 33 percent discard rate; Atlantic longline targeting swordfish and tuna having a 23 percent discard rate; and the New England/mid-Atlantic gillnet targeting ground-fish having a 16 percent discard rate.
So how do these population decreases affect the ecosystem as a whole? According to studies conducted by Brown et al. (1998, p. 9), “In the NW Atlantic, 55 percent of stocks of discarded fish species or species groups are having the health of their stock affected from discarding.” The most significant impacts of large bycatch numbers are felt on marine food webs (which will be discussed in greater detail in the following section). For example, when juvenile fish of a “valuable, overfished population” are captured as bycatch and discarded, it diminishes the opportunity for their species’ populations to recover from overfishing. Likewise, when other marine species regularly become bycatch, their populations rapidly decrease and subsequently create “holes” in their local food webs. Along with the impacts on the ecosystem, bycatch and its consequent discarding is also a great waste of oceanic resources. Often times, “target fish for one fishery are discarded as bycatch in a different fishery. For example, if New England trawl fishermen capture summer flounder but lack the permit to keep them, the fish are thrown overboard and wasted, often going undocumented.” Therefore, “discarding large quantities can lead to overfishing, prevent populations from recoveries after decades of overexploitation, and disrupt the natural balance of marine ecosystems” (Keledjian et al., 2014, p. 8).
Impacts of Overfishing on Marine Food Webs and its Biodiversity
The delicate composition of marine food webs are vital to the balance and overall health of marine ecosystems as a whole. “A healthy ecosystem is held together by its food webs” (Northwest Atlantic Marine Alliance [NAMA], 2015). Within a healthy ecosystem, there should exist a high level of biodiversity, which can be seen through the presence of both long and short food webs. Biodiversity is defined as, “the variety within and between all species of plants, animals, and micro-organisms and the ecosystems within which they live and interact” (WWF, 2015a). Therefore, when large numbers of different species’ populations are continually removed from the environment through commercial fishing, and harvested or discarded as bycatch, large gaps start to occupy their food webs.
This greatly alters the structure of the food web and leads to the decline, and eventual extinction, of some species, while simultaneously leading to the overpopulation of other species; thus disturbing the balance of the ecosystem and driving down biodiversity. To show the impacts overfishing is having on NW Atlantic food webs, this research will present the findings as it relates to each trophic level of average, healthy food webs. Trophic levels are defined by Encyclopedia Britannica as, “the steps in a nutritive series, or food web, of an ecosystem, with the organisms of a web classified into these levels on the basis of their feeding behavior” (which can change, as some organisms feed on several trophic levels).
The food webs in the NW Atlantic start at the first trophic level, which consists of the producers, such as tiny plants and algae comprising phytoplankton. This level fluctuates greatly each year and throughout different seasons, as natural, environmentally-driven factors (i.e. weather, sunlight, and oceanic currents) influence its size. This is normal, and in an ecosystem with healthy long and short food webs, the effects of these fluctuations are limited. Also, human factors such as water pollution and excessive nutrient run-off, along with impacts from invasive fishing gear, can have significant effects on the growth of these organisms.
The second trophic level consists of herbivorous (plant eating) consumers, such as zooplankton, krill, and forage fish like mackerel and herring. This is where the effects of overfishing start to significantly show. Due to larger, predatory fish species being the primarily targeted fish for centuries, their populations have decreased dramatically. This had resulted in the industry beginning to target smaller fish, lower in the food web. This has been come to be known as “fishing down the food web.”
Today, “forage fish typically account for more than 30 percent of the total fish caught annually” (Roney, 2013, para. 3). Most of these harvests are used for the extraction of their oil, along with the creation of fishmeal; which in turn, are used in various industries and products such as: fish farming, agriculture feed additive, pet food, fertilizers, and nutritional supplements for humans. Along with the threat of their populations from large catch totals, “forage fish stocks are highly sensitive to environmental change (due to their consumption of susceptible producers) and are prone to population crashes; so fishing levels considered safe in good years can be disastrous in bad ones” (Roney, 2013, para. 2).
The third trophic level consists of first level carnivorous consumers, such as: crustaceans (i.e. crabs, lobsters), juvenile stages of fish, and smaller fish (i.e. haddock, whiting). This is followed by the fourth trophic level, the second level carnivorous consumers, such as cod, saithe, and other predatory fish species. Next, the fifth trophic level, which is comprised of the third level carnivorous consumers, such as squid and seals. This is lastly followed by the sixth trophic level, which are top carnivores, often referred to as “apex predators.” These include species such as: bluefin tuna, shark, dolphin, and albatross.
Trophic levels three through six all share the similarity in which they are all carnivorous consumers; with the differences being in their status as prey for the levels above them, along with the available trophic levels below them in which they feed on. It should be noted that the previous examples of species in trophic levels three through six are subject to change based on the size and composition of the local food web. For example, in shorter, simpler food webs, a trophic level six species such as bluefin tuna may drop down to a level of 3 or 4, based upon length of prey between them and the primary producers.
The first effect of overfishing on these trophic levels is when their populations are decimated from high volumes of larger, mature individuals of these targeted species being caught. The second effect on these trophic levels relates back to bycatch. When juvenile fish of highly targeted species are accidentally caught and discarded, it greatly inhibits the species’ ability to recover to stable numbers. Along with the juvenile targeted species, the non-targeted species that become bycatch face population declines from not only their large bycatch numbers, but also from shortages of food from their prey facing overexploitation.
These overfishing effects have created a trophic cascade in the ecosystems of the NW Atlantic. This is defined as “an ecological phenomenon triggered by the addition or removal of top predators, and involving reciprocal changes in the relative populations of predator and prey through a food web” (Encyclopedia Britannica, n.d.). In some food webs, as upper level, predatory species are eliminated, the lower level prey become released from predation; which results in rising populations of lower level species. However, with the industry increasingly “fishing down the food web,” those released levels are actually now becoming exploited themselves, and are creating massive food shortages for the surviving, upper level species. This results in the large scale shrinking of food webs.
Overall, overfishing in the NW Atlantic has caused severe damage to its food webs, which is continually compromising the health of its marine ecosystems. “Interruptions in these food webs occurring when overfishing changes the balance of species, causing some species to decline or disappear; results in these ecosystems becoming biologically impoverished and less stable” (NAMA, 2015). As previously mentioned, healthy marine ecosystems are comprised of both long and short food webs. In some areas of open ocean, where there is little significant biomass, the simple food webs consist of only a few trophic levels at a given time. Biomass is defined as “the weight at a given time of all the animals and/or plants in a given ecosystem” (Pauly & Maclean, 2003, p. 47). This is in contrast to coastal areas which should often have ecosystems with longer, more complex food webs. To further show how overfishing has negatively impacted marine food webs and biodiversity, one can look at the mean trophic level of landed catch for all the fisheries in the entire NW Atlantic Ocean basin; which shows evidence of “fishing down the food web.”
Figure 1 of the trophic level trends, show an overall rapid decline of mean trophic levels in landings throughout the region since 1950. The sharp increase is explained by Pauly (2010, p. 39) as, “the fisheries were initially dominated by planktivorous menhaden and other, smaller pelagics (aside from cod) at low trophic levels, and as their landings decreased, the average trophic level of the fishery initially increased, then in the 1970s it reversed to a steep decline following increases in the targeting of forage fish.”
“Various studies have shown that such changes in catch composition indicate changes in relative abundance in the underlying ecosystems, and thus reflect the collapse of large populations (when trophic level declines are rapid) or the serial depletion of a number of smaller populations (when declines are gradual, but continuous over longer periods)” (Pauly & Maclean, 2003, p. 50).
This evidence shows that marine food webs in the NW Atlantic are shorter than ever and are overall, lacking the balance with larger food webs. This has driven down the biodiversity of these waters and created massive instability in its ecosystems. “Now in the NW Atlantic; the fishes that fisheries target tend to feed directly on a few species of plankton-feeding fishes, and thus are far more exposed than previously to seasonal and between-year changes of plankton abundance” (Pauly & Maclean, 2003, p. 56). This greatly impacts upper level consumers who are being faced with decreasing food sources. The biggest problem with these unstable ecosystems now consisting of mainly shorter food webs is that their decrease in biodiversity makes them more highly susceptible to succumb to other environmental pressures such as disease, pollution, and climate change; with less of a chance to bounce back and successfully recover.
Socioeconomic Impacts of Overfishing on Humans
While the effects of overfishing in the NW Atlantic are most severely felt on the environment, the impacts also impose negative effects on the social and economic pillars; not only in coastal communities, but for humans worldwide. “Currently, fish provides about 1.5 billion people with 20 percent of their animal protein, and provides another 3 billion people with at least 15 percent of such protein. However, as the demand for seafood increases, so will the price; resulting in billions of people unable to afford seafood due to increasing demand in wealthy nations, and vast commercial fleets that will out-compete local subsistence fishermen” (Jones, 2013, p. 2).
Along with other populations around the globe, seafood has long been a staple in meals for regional and coastal communities along the NW Atlantic coast. The past few hundred years have seen the cooking and consumption of seafood dishes grow into a tradition for these families. As the prices become unaffordable and the resources continue to diminish, a growing number of families will be forced to end these long-standing traditions and look for other options to fill this cultural void. Unfortunately, this end could be coming sooner than most think. “Overfishing is a time-sensitive issue, and if not addressed immediately, researchers and ecologists fear that the world could run out of seafood by 2048” (Jones, 2013, p. 3).
Not only does this directly impact the actual human consumption of seafood, but this will affect other products that consumers purchase. Sea products are now used by humans in a variety of ways, being an input in items such as: cosmetic products (i.e. make-ups and body washes); medical products (i.e. creams, nutritional supplements, and skin treatments); fertilizers; pet foods; and many other manufactured products. While prices for such items have already seen increases, the loss of a valuable input could threaten those industries as well.
Lastly, the loss of jobs in the commercial fishing industry has greatly impacted families in New England and Eastern Canada. In one example, “closures of the Canadian cod fisheries meant that by 1995, some 40,000 fishers and shore workers had been displaced, disrupting many coastal communities” (Pauly & Maclean, 2003, p. 16). This is particularly unfortunate because, although the local, inshore fishermen had long called for a bigger share of catch quotas, it was generally in response to the large, corporate fleets making their landings unprofitable and forcing them out of the market.
“The structure of the local, inshore fishery and the methods that were used in it meant that these fishermen did not have the capacity to greatly overfish the resource. They used fixed gear and small nets that could usually be manipulated by hand or with little mechanical assistance, never leading to anywhere near as high a catch as those taken by the corporate sector. As well, the crews tended to be composed of household and family members, and were usually not interested in running their operation as a business venture whose sole goal was the generation of profit. It was almost like a subsistence economy for many” (Mason, 2002, p. 3).
With the area continuing to be overfished, the overexploited stocks not recovering to commercial viability (or even environmental viability), and large corporate fleets with high-tech equipment and small crews dominating the inshore and offshore operations; most of the unemployed fishermen were forced to find new work outside the industry. Thus breaking years, and in some cases, centuries, of family tradition working in the fishing industry. In many places, such as Newfoundland, Labrador, coastal Maine, and Massachusetts, many of the displaced workers and their families have suffered greatly from a lack of work. This is because jobs are scarce in these places, where fishing had been the main economic industry for hundreds of years.
Conclusion
In conclusion, overfishing has negatively affected every aspect of marine ecosystems in the NW Atlantic. It has caused the large-scale destruction and loss of marine habitats; decimated populations of non-targeted species and unconsumed targeted species (wasting valuable resources); shortened food webs; extirpated species; and significantly decreased overall biodiversity. In turn, this has decreased the overall health of these ecosystems; making them fragile, unstable, and highly susceptible to other environmental and human-influenced factors.
While some may argue that the decline of marine ecosystems in the NW Atlantic (and globally) is attributed to these other factors; there is no denying the historical buildup of evidence that suggests overfishing as having the most damaging effects on marine ecosystems. “While it is often overlooked for other environmental issues, overfishing has historically caused more ecological extinction than any other human influence on coastal ecosystems, including water pollution. Unfortunately, due to a lack of data, the extent of this damage has only recently been recognized” (Dartmouth Undergraduate Journal of Science, 2012, para. 11).
Many species from these waters are gone forever, and many remaining species are overexploited to the point where their recovery is debated and largely unknown. While overfishing has greatly altered the ecological composition of these waters from the days of pre-European arrival; it is unknown whether these ecosystems can even rebound enough to hold healthy, sustainable, and biologically diverse populations of plant and animal species. However, one thing is certain amongst most scientists; if current practice is not quickly and drastically changed to more sustainable fishing and management methods, these important marine ecosystems and valuable resources will be lost forever.
As that time quickly approaches, humans will also continue to feel the increasing social and economic ramifications of this problem. As John Muir, the renowned environmentalist and founder of the Sierra Club once stated, “When we try to pick out anything by itself, we find it hitched to everything else in the universe” (as cited in Sierra Club, n.d.).
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