Fisheries

Category: Inland Aquatic Biomes; Marine and Oceanic Biomes.

Geographic Location: Global.

Summary: The world's fisheries face threats from overfishing, destructive methods, and climate change that could impact global food sources.

Fisheries is the term used to define industries involved in the harvesting, processing, and marketing of aquatic products. In a broad sense, fisheries is a term used to describe areas of water bodies, species of organisms being harvested, methods of harvesting, and the people involved in any of these processes. Fisheries products are not limited to fish; rather they include the entire span of aquatic organisms, both marine and freshwater. There is a great variety of such resources—and great challenges in terms of the sustainability of major fisheries in the face of regional and global ecosystem changes.

Fisheries Products

Aquatic organisms such as fish are among the most readily available protein sources in many countries. According to the United Nations Conference on Trade and Development (UNCTAD), fish accounted for approximately 17 percent of global animal protein consumption in 2019, and fisheries provide the general population with access to these protein sources. Aquatic organisms included in the fisheries designation include seaweeds, cnidarians (jellyfish), echinoderms (sea cucumbers), crustaceans (crabs and shrimp), mollusks (snails, limpets, bivalves, squid, cuttlefish, and octopuses), marine reptiles (sea turtles), fish (cartilaginous and bony), marine mammals (manatees, dugongs, porpoises, sea lions, and whales), and even the marine worms (peanut worms) that are harvested in parts of Asia.

Aquatic organisms that are sold alive or chilled command the highest prices. Live seafood is extremely popular in countries in east Asia, such as China (especially in Hong Kong), Singapore, and Taiwan, where they fetch prices multiple times higher than those of frozen fish. Fresh fisheries products are those that have been chilled over short periods; these also cater to the people of Japan and Japanese restaurants all over the world as sashimi. To extend shelf life, aquatic organisms are processed in various ways, often via freezing, canning, fermenting, or drying, which dramatically reduces their cost as compared to fresh goods.

Fisheries products also refer to parts, by-products, or processed aquatic organisms. Caviar, caviar substitutes (roe from nonsturgeon fish), and roe from other marine organisms such as shrimp are included. Mollusks are harvested for nacre, a lustrous substance from which pearls and mother-of-pearl are made. Shark and ray skins are by-products that can be made into leather. Other by-products of fisheries include trash fish or unwanted fish parts that are ground up to make fish meal, which is used in feed for pets, cultured fish, and livestock.

Capture Fisheries

Capture fisheries is a term used for exploiting resources from the wild. Capture fisheries in marine environs occur at near-shore areas such as estuaries, mangroves, and coral reefs; or at offshore areas such as open oceans and seamounts. Capture fisheries also occur in lotic (moving water) habitats like freshwater streams and rivers, or in lotic freshwater lakes. There are several scales at which capture fisheries occur: commercial, artisanal, and recreational. Commercial or industrial fisheries are typically large-scale, and meet the demands of a broader national or international market. Artisanal or subsistence fisheries cater to local demands or are self-sufficient. Recreational fisheries are exclusively for pleasure and not for commercial purposes.

Fishing Down the Food Web

The post–World War II period saw an increase in commercial fishing that has resulted in greater (by tonnage) yields. The ability to capture more fish through better-equipped commercial vessels and more effective means of capture allowed for increased exploitation of aquatic resources. The sharp increase in the number, size, and engine power of vessels allowed for extended periods at sea. The spatial and temporal intensity of exploitation, along with evolved fishing gear, enhanced skills of fishers, and high catch efforts contributed to increased landings. Computers installed in fishing vessels to locate positions of shoals allowed for precision in harvesting. Intensive commercial fishing from the 1960s through the 1990s thereby saw the rapid depletion of global fisheries resources.

The compositions of captured fisheries transited from organisms high in the trophic level, such as carnivorous fishes, to those low in the trophic level, such as invertebrates and planktivorous fishes. The term fishing down the food web has been coined to describe this phenomenon.

Initially, global landings of organisms lower in the trophic levels were high, but soon stagnated or declined as overharvesting persisted. Countries where fisheries biomass decreased moved their efforts to deeper waters. Scientists have arrived at a consensus that the propensity for slow growth rates and high longevity of deepwater organisms render this resource type unsustainable.

Some researchers argue that collapses in various fisheries occurred before the 20th century. This conclusion was reached via paleoecological records from marine sediments; archaeological records from ancient human settlements; historical written records, journals, and documents; and ecological records from scientific literature for more than a century. A group of scientists led by Jeremy Jackson (Scripps Institution of Oceanography at the University of San Diego), for example, studied patterns of population abundances and crashes of harvested marine organisms.

Such scientists postulated that larger marine organisms were already trending toward population crashes before the twentieth century. Citing, among others, the example of the Steller's sea cows that became extinct in 1768, the scientists stated their belief that aboriginal hunting was responsible for decimating populations throughout the northern Pacific Rim.

Similar patterns were observed for organisms such as whales, dugongs, fur seals, and turtles, the difference being that small isolated populations of those species still exist. Global colonial infiltrations and the advent of vessels capable of long-haul cruises sealed the fate of these organisms. The dramatic reduction in populations of these organisms altered coastal ecosystems significantly and eventually led to the crashes presently observed. These authors did not discount the fact that the intensity and persistence of current exploitation of fisheries resources are unsustainable and, if continued unchecked, will lead to systemic ecosystem collapses in the future.

Current trends show that global fishing efforts are estimated to exceed the optimum factor by three- to fourfold. Excess fishing efforts contribute to billions of dollars in yearly losses through four main avenues: increased fishing, declining fishing stocks, stagnating or declining resource prices, and fishing subsidies that support over­exploitation. The Food and Agriculture Organization of the United Nations (FAO) report based on data from 2007 showed that global fisheries were facing inevitable crashes. A total 52 percent of all fish stocks were already overexploited, 28 percent were overexploited or depleted, 20 percent were moderately exploited, and only 1 percent showed signs of recovery. According to the Geneva Environmental Network, in 2022, approximately 90 percent of the world's fish stocks were fully exploited, overexploited, or depleted.

In 2022, capture fisheries' production was approximately 100 million tons (90.7 million metric tons), according to the FAO. If the current levels of capture fisheries continues, some scientists estimate that global fisheries will collapse by the mid-twenty-first century, with only smaller fish surviving.

Fisheries Collapse

There are two major persistent problems related to fisheries: bycatch and bottom trawling.

Bycatch is the incidental capture of nontarget fisheries that are often of no economic concern due to their low commercial value. At times, these are nontargeted species or species that are discarded due to their size. Often, organisms such as echinoderms, crustaceans, turtles, marine mammals, and birds are entangled in the nets set out for commercially targeted fish. Marine cetaceans often get entangled and consequently drown in tuna fisheries. Marine birds, and large marine organisms such as turtle and sharks, often are entangled in longlines when trying to obtain baited hooks targeting tuna, swordfish, and halibut.

Bycatches have been identified as the cause of the dramatic decline in many marine species. The unintentional yet systematic removal of nontarget species from the environment has strong ecological implications; it is considered one of the greatest threats to the marine environment. The highest incidence of bycatches is associated with shrimp capture fisheries, with shrimp capture responsible for a significant percent of total global bycatch.

Trawling is a fishing method involving the use of large nets and mechanized arms on fishing vessels. The nets are set into the water at specified depths and pulled through the water column over a period of time. Bottom trawling occurs when the net is dragged over the seabed, targeting marine organisms living on the seabed or just above it, such as bottom fish, shrimp, and squid. This method of fishing has been associated with heavy, negative effects on seabed communities. Nets dragged over the seabed not only cause seabed sediments to be suspended in the water column, but also physically damage reefs and deepwater corals. In addition, catches made by this method are nondiscriminatory in nature, resulting in large volumes of bycatches.

Global Change and Fisheries

Scientists believe that in the chronological chain of events, factors such as pollution, physical destruction of habitats, and anthropogenic climate change are factors affecting fisheries. However, human-induced climate change has been a particularly confounding factor. Coupled with overexploitation, the effects of climate change on fisheries are only now beginning to be understood.

The oceans, being open systems, are governed by many interacting factors, which are often difficult to elucidate in isolation. It is generally agreed, however, that changes in the climate will cause distinct changes in the patterns of distribution of important fisheries resources. Marine organisms are likely to respond to global warming through shifts in latitudinal ranges, for instance. Consequently, local extirpations, invasions by other organisms, and changes in the population structure of remaining or newly invaded species are likely to occur. In short, resultant community interactions for such ecosystems also are likely to change.

Mitigation Measures

Farmed fisheries for both freshwater and marine organisms have been touted as the solution to meet increased demand for a waning natural supply. Economically important aquatic organisms are farmed either ex-situ in facility tanks; in-situ at enclosed inlets or bays; or in sea cages and pens. In 2014 alone, production from farmed fisheries made up 44.1 percent of total production by farmed fisheries and capture fisheries combined, according to the FAO.

However, several concerns about this industry have arisen. Large tracts of mangrove forests, particularly in southeast Asia, have been cleared to make way for unsustainable coastal shrimp and fish farms. With increasing bioaccumulation and toxin buildup over time, these areas are abandoned, and new mangrove areas are then deforested. Many aquafarms also are fundamentally nonsustainable, requiring that fingerlings and hatchlings of aquatic organisms are still harvested from the wild and are only grown and fattened in farmed areas.

The introduction of antibiotics to farmed organisms, especially if these areas are connected to natural water bodies or other natural ecosystems, is a concern among many environmentalists who fear that resistance to parasites and disease is undermined by the overuse of antibiotics. The biological discharge from aquatic farms to the natural environment raises similar concerns. Yet another issue surfaced when it was found that fish farms consumed more wild fish than their final output. This situation has been monitored, and scientists are still refining ways to produce farmed aquatic resources with minimal environmental effect.

A major challenge faced by managers of aquatic ecosystems is illegal fishing. For example, in some reefs around southeast Asia, dynamite fishing was rife in past decades. Increased efforts by managers of marine ecosystems to curtail bombing of coral reefs have caused dynamite fishing to subside somewhat. Both the live-seafood and marine-aquarium trades are booming, with much of the resource base centering on southeast Asian seas. The use of low doses of cyanide to stun and capture live marine organisms is common in parts of southeast Asia.

The effects of this method of marine-organism collection are continuously being studied. In addition to the obvious removal of selected organisms, cyanide remains in the ecosystem and affects the remaining sea life. Catch efforts in intertidal pools are especially deleterious for all creatures left in the pools postcollection. Corals are known to be affected by cyanide, with reports of decreased productivity by symbiotic zooxanthallae. Because of such negative effects, beginning in 2018, researchers were working on perfecting a method for breeding those fish species of the most value to collectors (particularly tropical) in tanks. Managers of aquatic ecosystems are aware that these activities persist but face constraints in the implementation of maritime laws, due largely to enforcement agencies' insufficient capacities to patrol the areas under their purview.

The Way Forward

Stakeholders in the industry are making some progress in dealing with bycatches. Trawl nets have been redesigned to aid in excluding several species of organisms, notably turtles, for which turtle excluder devices have been created. These nets are equipped with a device above or below the nets so that large organisms can escape unharmed. Efforts such as those by World Wildlife Fund (WWF) in 2005–09 to reward innovative ideas to reduce bycatches have been seen as a positive step toward solving global problems as a global community. With WWF and interested stakeholders such as the US National Oceanic and Atmospheric Administration (NOAA) and the US Department of Fisheries, some of these novel ideas are being refined and tested to assess their suitability for broad use by the industry. In the NOAA report, 2021 Status of Stocks, more than 460 stocks were managed by NOAA Fisheries. In 2021, US fisheries were holding steady with 90 percent of stocks not subject to overfishing, and 80 percent with population sizes large enough to be considered not overfished.

According to the Database of World Protected Areas, in 2022 there were nearly eighteen thousand marine protected areas, and there are different scientific recommendations for their use. In some areas, partial exploitation is allowed. In others, there are strict no-take zones where no fisheries activities are allowed. There also exists direct evidence of positive spillover effects, where larvae borne from organisms in protected areas are able to seed neighboring reefs.

The constant efforts by aquatic ecosystem managers and scientists to understand the processes behind the ecosystems under their care serve to improve the management of these imperiled ecosystems and, by extension, enhance the management of fisheries resources. These efforts are especially pertinent in open systems such as the oceans, where connectivity and common resources call for the participation of all stakeholders. Global initiatives led by organizations such as FAO are beneficial in elucidating ways in which fisheries-dependent countries can work together to achieve sustainable resources for the future.

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