The environmental impact of fishing includes issues such as the availability of fish, overfishing, fisheries, and fisheries management; as well as the impact of industrial fishing on other elements of the environment, such as bycatch. These issues are part of marine conservation, and are addressed in fisheries science programs. According to a 2019 FAO report, global production of fish, crustaceans, molluscs and other aquatic animals has continued to grow and reached 172.6 million tonnes in 2017, with an increase of 4.1 percent compared with 2016. There is a growing gap between the supply of fish and demand, due in part to world population growth.
Fishing and pollution from fishing are the largest contributors to the decline in ocean health and water quality. Ghost nets, or nets abandoned in the ocean, are made of plastic and nylon and do not decompose, wreaking extreme havoc on the wildlife and ecosystems they interrupt. The ocean takes up 70% of the earth, so overfishing and hurting the marine environment affects everyone and everything on this planet. On top of the overfishing, there is a seafood shortage resulting from the mass amounts of seafood waste, as well as the microplastics that are polluting the seafood consumed by the public. The latter is largely caused by plastic-made fishing gear like drift nets and longlining equipment, that are wearing down by use, lost or thrown away.
The journal Science published a four-year study in November 2006, which predicted that, at prevailing trends, the world would run out of wild-caught seafood in 2048. The scientists stated that the decline was a result of overfishing, pollution and other environmental factors that were reducing the population of fisheries at the same time as their ecosystems were being annihilated. Many countries, such as Tonga, the United States, Australia and Bahamas, and international management bodies have taken steps to appropriately manage marine resources.
Reefs are also being destroyed by overfishing because of the huge nets that are dragged along the ocean floor while trawling. Many corals are being destroyed and, as a consequence, the ecological niche of many species is at stake.
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Some fishing techniques cause habitat destruction. Blast fishing and cyanide fishing, which are illegal in many places, harm surrounding habitats. Blast fishing refers to the practice of using explosives to capture fish. Cyanide fishing refers to the practice of using cyanide to stun fish for collection. These two practices are commonly used for the aquarium trade and the live fish food trade. These practices are destructive because they impact the habitat that the reef fish live on after the fish have been removed. Bottom trawling, the practice of pulling a fishing net along the sea bottom behind trawlers, removes around 5 to 25% of an area's seabed life on a single run. Most of the impacts are due to commercial fishing practices. A 2005 report of the UN Millennium Project, commissioned by UN Secretary-General Kofi Annan, recommended the elimination of bottom trawling on the high seas by 2006 to protect seamounts and other ecologically sensitive habitats. This was not done.
In mid-October 2006, United States President George W. Bush joined other world leaders calling for a moratorium on deep-sea trawling. The practice has shown to often have harmful effects on sea habitat and, hence, on fish populations, yet no further action was taken (Vivek). The sea animal's aquatic ecosystem may also collapse due to the destruction of the food chain.
Additionally, ghost fishing is a major threat due to capture fisheries. Ghost fishing occurs when a net, such as a gill net or trawl, is lost or discarded at sea and drifts within the oceans and can still act to capture marine organisms. According to the FAO Code of Conduct for Responsible Fisheries, States should act to minimize the amount of lost and abandoned gear and work to minimize ghost fishing.
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area. Overfishing can occur in water bodies of any sizes, such as ponds, wetlands, rivers, lakes or oceans, and can result in resource depletion, reduced biological growth rates and low biomass levels. Sustained overfishing can lead to critical depensation, where the fish population is no longer able to sustain itself. Some forms of overfishing, such as the overfishing of sharks, has led to the upset of entire marine ecosystems. Types of overfishing include: growth overfishing, recruitment overfishing, ecosystem overfishing.
The ability of a fishery to recover from overfishing depends on whether its overall carrying capacity and the variety of ecological conditions are suitable for the recovery. Dramatic changes in species composition can result in an ecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before the depletion of the original fish stock. For example, once trout have been overfished, carp might exploit the change in competitive equilibria and take over in a way that makes it impossible for the trout to re-establish a breeding population.
Since the growth of global fishing enterprises after the 1950s, intensive fishing has spread from a few concentrated areas to encompass nearly all fisheries. The scraping of the ocean floor in bottom dragging is devastating to coral, sponges and other slower-growing benthic species that do not recover quickly, and that provide a habitat for commercial fisheries species. This destruction alters the functioning of the ecosystem and can permanently alter species' composition and biodiversity. Bycatch, the collateral capture of unintended species in the course of fishing, is typically returned to the ocean only to die from injuries or exposure. Bycatch represents about a quarter of all marine catch. In the case of shrimp capture, the bycatch is five times larger than the shrimp caught.A report by FAO in 2020 stated that "in 2017, 34 percent of the fish stocks of the world’s marine fisheries were classified as overfished".: 54 Mitigation options include: Government regulation, removal of subsidies, minimizing fishing impact, aquaculture and consumer awareness.
Overfishing can result in the over-exploitation of marine ecosystem services. Fishing can cause several negative physiological and psychological effects for fish populations including: increased stress levels and bodily injuries resulting from lodged fish hooks. Often, when this threshold is crossed, hysteresis may occur within the environment. More specifically, some ecological disturbances observed within the Black Sea marine ecosystem resulted from a combination of overfishing and various other related human activities which adversely affected the marine environment and ecosystem. Ecological disruption can also occur due to the overfishing of critical fish species such as the tilefish and grouper fish, which can be referred to as ecosystem-engineers.
Fishing may disrupt food webs by targeting specific, in-demand species. There might be too much fishing of prey species such as sardines and anchovies, thus reducing the food supply for the predators. Disrupting these types of wasp-waist species may have effects throughout the ecosystem. It may also cause the increase of prey species when the target fishes are predator species, such as salmon and tuna.
Overfishing and pollution of the oceans also affect their carbon storage ability and thus contribute to the climate crisis.
Main article: Fisheries-induced evolution
Fisheries-induced evolution or evolutionary impact of fishing is the various evolutionary effects of the fishing pressure, such as on size or growth. It is manly caused by selective fishing on size, bigger fish being more frequently caught. Moreover, policy of minimum landing size, based on the idea that it spares young fishes, have many negative impacts on a population by selecting slow growth individuals.
Main article: Bycatch
Bycatch is the portion of the catch that is not the target species. These are either kept to be sold or discarded. In some instances the discarded portion is known as discards. Even sports fisherman discard a lot of non-target and target fish on the bank while fishing. For every pound of the target species caught, up to 5 pounds of unintended marine species are caught and discarded as bycatch. As many as 40% (63 billion pounds) of fish caught globally every year are discarded, and as many as 650,000 whales, dolphins and seals are killed every year by fishing vessels.
Main article: Shark finning
Shark finning is the act of removing fins from sharks and discarding the rest of the shark. The sharks are often still alive when discarded, but without their fins. Unable to swim effectively, they sink to the bottom of the ocean and die of suffocation or are eaten by other predators. Though studies suggest that 73 million sharks are finned each year, scientists have noted that the numbers may actually be higher, with roughly 100 million sharks being killed by finning each year. The deaths of millions of sharks has caused catastrophic damage to the marine ecosystem.
Main article: Shark culling
Shark culling is the killing of sharks in government-run "shark control" programs. These programs exist to reduce the risk of shark attacks — however, environmentalists say that they do not reduce the risk of shark attacks; they also say that shark culling harms the marine ecosystem. Shark culling currently occurs in New South Wales, Queensland, KwaZulu-Natal and Réunion. Queensland's "shark control" program killed roughly 50,000 sharks between 1962 and 2018 — Queensland's program uses lethal devices such as shark nets and drum lines. Thousands of other animals, such as turtles and dolphins, have been killed in Queensland as bycatch. Queensland's shark culling program has been called "outdated, cruel and ineffective". The shark culling program in New South Wales (which uses nets) has killed thousands of sharks, turtles, dolphins and whales. KwaZulu-Natal's shark culling program killed more than 33,000 sharks in a 30-year period.
Main article: Marine debris
Recent research has shown that, by mass, fishing debris, such as buoys, lines, and nets, account for more than two-thirds of large plastic debris found in the oceans; in the Great Pacific Garbage Patch, fishing nets alone comprise at least 46% of the debris. Similarly, fishing debris has been shown to be a major source of plastic debris found on the shores of Korea. Marine life interacts with debris in two ways: either through entanglement (where debris entangles or entraps animals), or ingestion of the debris (either intentionally or accidentally). Both are harmful to the animal. Marine debris consisting of old fishing nets or trawls can often be linked to phenomena such as ghost fishing, wherein the netting debris, referred to as ghost nets, continues to entangle and capture fish. A study performed in southern Japan on octopuses noted that there was an estimated mortality rate of 212,000–505,000 octopuses per year within the area's fishing grounds, due in large part to ghost fishing. Tracking garbage and monitoring the logistics of human waste disposal, especially waste materials primarily associated with fishing, is one method to reduce marine debris. Using technological or mechanical innovations such as marine debris-clearing drones can further serve to reduce the amount of debris within oceans.
Main article: Recreational fishing
Recreational fishing is fishing done for sport or competition, whereas commercial fishing is catching seafood, often in mass quantities, for profit. Both can have different environmental impacts when it comes to fishing.
Though many assume recreational fishing does not have a large impact on fish, it actually accounts for almost a quarter of the fish caught in the United States, many of those being commercially valuable fish. Recreational fishing has its biggest impact on marine debris, overfishing, and fish mortality. Release mortality in recreational fisheries is the same as the impacts of bycatch in commercial fisheries. Studies have suggested that improving recreational fisheries management on a global scale could generate substantial social benefits of the same scale as reforming commercial fisheries.
Catch and release fishing involves several practices to reduce the negative environmental impacts of fishing that include: the duration, timing, and type of hook used during angling. To increase the effectiveness of catch and release fishing and mitigate its negative impacts, species-specific guidelines are required. These guidelines help tailor specific rules and regulations to specific species of fish in relation to their locations and mating and migration cycles. A metastudy in 2005 found that the average catch and release mortality rate was 18%, but varied greatly by species. While catch-and-release fishing has been wildly used in recreational fishing, it is also beneficial for maintaining fish populations at a stable level for commercial fisheries to receive social and economic benefits. Combining catch and release fishing with biotelemetry data collection methods allows for researchers to study the biological effects of catch and release fishing on fish in order to better suit future conservation efforts and remedies.
One method to increase fish population numbers and reduce the severity of adverse environmental impacts and ecological disturbances is the utilization of traditional fisheries management systems within fisheries. Essentially, traditional fisheries management incorporates the aspects of fisheries management; however, the conservation efforts take into account concepts that place restrictions on the type of gear used and the allotment of permitted angling. Traditional fisheries management also incorporates communities within its conservation efforts which often result in management scenarios where there is co-management conservation efforts led by communities.
Ecosystem-based management of fisheries is another method used for fish conservation and impact remediation. Instead of solely focusing conservation efforts on a single species of marine life, ecosystem-based management is used across various species of fish within an environment. To improve the adoption of these types of fisheries management, it is important to reduce barriers to entry for management scenarios in order to make these methods more accessible to fisheries globally.
Many governments and intergovernmental bodies have implemented fisheries management policies designed to curb the environmental impact of fishing. Fishing conservation aims to control the human activities that may completely decrease a fish stock or washout an entire aquatic environment. These laws include the quotas on the total catch of particular species in a fishery, effort quotas (e.g., number of days at sea), the limits on the number of vessels allowed in specific areas, and the imposition of seasonal restrictions on fishing.
In 2008, a large scale study of fisheries that used individual transferable quotas and ones that didn't provide strong evidence that individual transferable quotas can help to prevent collapses and restore fisheries that appear to be in decline.
Fish farming has been proposed as a more sustainable alternative to traditional capture of wild fish. However, fish farming has been found to have negative impacts on nearby wild fish and farming of predatory fish like salmon can rely on fish feed that is based on fish meal and oil from wild fish.
Further information: Marine protected area
Marine reserves serve to foster both environmental protection and marine wildlife safety. The reserves themselves are established via environmental protection plans or policies which designate a specific marine environment as protected. Coral reefs are one of the many examples which involve the application of marine reserves in establishing marine protected areas. There have also been marine reserve initiatives located in the United States, Caribbean, Philippines and Egypt. To mitigate the negative environmental impacts of fishing within marine environments, marine reserves are intended to create, enhance and re-introduce biodiversity within the area. As a result, the primary benefits arising from the implementation of this type of management effort include positive impacts towards habitat protection and species conservation.
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