Overfishing
Up to a certain point, fishermen are able to catch fish without damaging the ecological balance. This is known
FIGURE 4.10 Effects of siltation on aquatic life
Overfishing removes fish faster than they can reproduce and causes serious population declines. This can have far-reaching consequences on other species that rely on the depleted fish for food. Furthermore, once fishermen deplete all the large fish of a species, they often begin to target smaller, younger individuals. Targeting young fish undermines future breeding populations and guarantees a smaller biological return in future years. Swordfish have been seriously depleted in this way. In the early 1900s the average weight of a swordfish when caught was about 300 pounds. By 1960, according to the NMFS, it was 266 pounds, and at the close of the twentieth century it was ninety pounds.
Technological advances have enabled numerous marine fisheries to be depleted in a short amount of time. The U.S. Commission on Ocean Policy published An Ocean Blueprint for the 21st Century (September 2004, http://www.oceancommission.gov/documents/full_color_rpt/welcome.html). Commission members were appointed by President George W. Bush to develop recommendations for a new national ocean policy. The report noted: "Experts estimate that 25 to 30 percent of the world's major fish stocks are over-exploited, and many U.S. fisheries are experiencing serious difficulties."
MAGNUSON-TEVENS ACT
The U.S. government attempted to eliminate overfishing in U.S. coastal waters by passing the Magnuson-Stevens Fishery Conservation and Management Act (P.L. 94-265) in 1976. This act established U.S. control over fishery resources within 200 nautical miles of the coast. (See Figure 4.12.) This area was later deemed the Exclusive Economic Zone (EEZ). Under international law the United States has sovereign rights to explore, exploit, conserve, and manage living and nonliving resources within and below ocean waters within the EEZ.
FIGURE 4.11 The marine food chain
When the Magnuson-Stevens Act was passed it prevented foreign fishing fleets from exploiting the affected waters. However, with foreign fleets gone, American fishermen built up their own fleets, buying large, well-equipped vessels with low-interest loans from the federal government. For several years U.S. fishermen reported record catches. Then these declined.
The act established eight Regional Fishery Management Councils as follows:
- Caribbean Fishery Management Council
- Gulf of Mexico Fishery Management Council
- Mid-Atlantic Fishery Management Council
- New England Fishery Management Council
- North Pacific Fishery Management Council
- Pacific Fishery Management Council
- South Atlantic Fishery Management Council
- Western Pacific Fishery Management Council
The councils were instructed to prepare Fishery Management Plans (FMPs) covering domestic and foreign fishing efforts within their area of authority. FMPs must be approved by the Secretary of Commerce before being implemented. They are enforced by the National Marine Fisheries Service and the U.S. Coast Guard. The Fishery Management Plans for some species, such as highly migratory fishes that enter and leave the Exclusive Economic Zone, are prepared by the U.S. Department of Commerce. As of February 2006 more than forty FMPs have been finalized for various species. The plans can be accessed at the Web site http://www.nmfs.noaa.gov/sfa/domes_fish/FMPS.htm.
The Fishery Management Councils were intended to eliminate overfishing, while ensuring that the "optimum yield" was obtained from each fishery. Critics say the system has failed to do this. The National Academy of Public Administration in Courts, Congress, and Constituencies: Managing Fisheries by Default (July 2002, http://www.napawash.org/Pubs/NMFS_July_2002.pdf? OpenDocument) concluded that fisheries management in the United States was being driven by litigation and political processes, rather than sound science. At that time more than 100 lawsuits were pending against the NMFS; most involved stock assessments and catch limits and were filed by the fishing industry or conservation groups.
The Ocean Blueprint for the 21st Century complains: "Social, economic, and political considerations have often led the Councils to downplay the best available scientific information, resulting in overfishing and the slow recovery of overfished stocks." However, the report does acknowledge that overfishing has been relieved in some areas. During the 1990s increases were reported in stocks of Mid-Atlantic flounder, New England ground-fish, and Atlantic striped bass.
SHARK OVERFISHING
According to the San Diego Natural History Museum, sharks have been predators of the seas for nearly 400 million years. There are more than 350 species of sharks, ranging in size from the tiny pygmy shark to the giant whale shark.
Shark populations are being decimated because of the growing demand for shark meat and shark fins. Fins and tails sell for as much as $100 a pound. In 2003 the Pew Institute for Ocean Science instituted a project called the Pew Global Shark Assessment. Its purpose is to collect data regarding declines in global shark populations. According to the project's Web site (http://www.pewoceanscience.org/projects/Pew_Global_Shar/intro.php?ID=56) populations of dusky, oceanic whitetip, and silky sharks in the Gulf of Mexico have declined by
FIGURE 4.12 Federal and state jurisdiction over offshore waters
Biologists Julia Baum and Ransom Myers of Dalhousie University in Canada in "Collapse and Conservation of Shark Populations in the Northwest Atlantic" (Science, January 17, 2003), showed that many shark populations in the Gulf of Mexico have plummeted since the 1950s. In particular, whitetip shark populations have declined by 90%. The researchers blamed the decline on overfishing due to demand for sharkfin soup, which is considered a luxury. Myers said, "Researchers in the 1960s suggested that oceanic whitetip sharks were the most common large species on Earth. What we have shown is akin to the herds of buffalo disappearing from the Great Plains and no one noticing." Other species which have been affected include the silk shark, whose populations have dropped by 90%, and the mako shark, which has declined 79%.
FISH DECLINES AND DEEP-SEA HARVESTING
As catches of shallow water fishes decline, trawlers have increasingly been used to scour the deep seas for new varieties of fish, such as the nine-inch long royal red shrimp, rattails, skates, squid, red crabs, orange roughy, oreos, hoki, blue ling, southern blue whiting, and spiny dogfish. Although limited commercial deep-sea fishing has occurred for decades, new technologies are making it considerably more practical and efficient. As stocks of better-known fish shrink and international quotas tighten, experts say deep ocean waters will increasingly be targeted as a source of seafood.
Bycatch
Bycatch is the term used for nontargeted animals captured during fishing. For example, during the 1960s, hundreds of thousands of dolphins per year were caught in the nets of tuna fishing boats and drowned. Although dolphins were not the targets of the fishing operations, they became victims anyway. Public outcry over dolphin deaths led to passage of the Marine Mammal Protection Act and promises by tuna canneries to sell only "dolphin-safe" tuna. Unfortunately bycatch continues to be a problem for many aquatic species, including those that are endangered and threatened.
FROM DRIFT NETS TO LONGLINES
Drift nets are the world's largest fishing nets, reaching lengths of up to thirty miles. Conservationists refer to them as "walls of death" because they indiscriminately catch and kill marine species. Over 100 species—including whales, sea turtles, dolphins, seabirds, sharks, salmon, and numerous other fish species—have been killed in drift nets. Drift nets were eventually banned because of their destructive-ness to wildlife.
After the banning of drift nets, many fishermen turned to longlines. Longlines are fishing lines with a single main line attached to many shorter lines that terminate in baited hooks. They are used to catch wide-ranging oceanic species such as tuna, swordfish, and sharks, as well as bottom dwellers such as cod and halibut. A single boat can trail thousands of hooks from lines stretching twenty to eighty miles.
Longline fishing kills fewer marine mammals than drift nets but captures more surface-feeding sea birds, particularly the rare albatrosses. Longline fishing has in fact resulted in the decline of numerous albatross species, almost all of which are now listed by the World Conservation Union (IUCN) as endangered. Australian scientists estimate that longline fishing kills more than 40,000 albatrosses each year. Longline fishing has also caused rapid declines in some fish species. Longlining is an old practice, but modern technology has vastly increased its efficiency and ecological impact.
Ghost Fishing
"Ghost fishing" is a term used by biologists to refer to the accidental entanglement of aquatic animals in abandoned or lost fishing gear. According to the 2004 report An Ocean Blueprint for the 21st Century ghost fishing kills hundreds of thousands of marine mammals worldwide each year. Dolphins, porpoises, and small whales are the primary victims. However, even large whales can be injured by entanglements or become exhausted after towing heavy nets and gear over long distances. Ghost fishing is one of the main causes blamed for the endangered status of the North Atlantic right whale.
Ghost fishing is an international problem. The U.S. Commission on Ocean Policy reports that between 1998 and 2002 more than 150 tons of fishing nets and lines were removed from reefs near the northwestern Hawaiian Islands. Oftentimes the nets were not the type used by local fisheries; instead, they are believed to have drifted from thousands of miles away in the North Pacific Ocean. Possible solutions to the problem of ghost fishing include the assessment of fees or deposits on fishing nets with the money raised used to collect derelict fishing gear, achieving international cooperation in identifying and removing derelict fishing gear, and development of biodegradable fishing gear. The NMFS already requires commercial U.S. fisheries to mark fishing gear with identifying information.
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