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The depletion of food supplies is not the only risk to marine wildlife populations from commercial fisheries. Millions of marine animals other than fish are severely injured or killed each year through deadly interactions with fishing operations. Many populations of marine wildlife species are threatened or have become endangered, to such an extent that some, like the albatross, are sliding toward extinction.
One of the most notorious and long-standing problems in this regard has been in commercial tuna purse seine fisheries in the eastern tropical Pacific (ETP) ocean off Mexico and Central America. For unknown reasons, yellowfin tuna in the ETP commonly swim beneath herds of dolphins and other species such as whales and whale sharks as they migrate through the open oceans. Using floating nets in excess of 2000 meters long, ETP tuna fishing fleets deliberately encircled dolphins, whales or sharks in order to catch the tuna below them.
Since 1959, when the U.S. tuna fleet introduced the practice, an estimated seven million dolphins in the ETP tuna fishery perished, of which about five million were from one species - the northern offshore spotted dolphin. Because the fishing fleets were not controlled, many dolphin populations had become severely reduced by the 1970s. Today, dolphin deaths in this fishery are declining because of an international agreement to bring the fleets under control, including a regulation that all tuna purse seine boats fishing in the ETP must carry professional observers.
Much less is known about the numbers of dolphins and other animals captured and killed in the other purse seine tuna fisheries in the Pacific, Atlantic and Indian Oceans. This is because it is ONLY in the eastern Pacific where the scientific observers are required on ALL commercial tuna vessels. Many populations of dolphins, sharks, whales, even endangered sea turtles could be threatened by purse seine fishing operations, but little remedial action can be taken as long as the companies of the global tuna industry are successful in keeping their impact secret.
During the 1980s, when more than 50,000 kilometer's (32,000 miles) of driftnets were being set in the Pacific Ocean each night, many types of marine animals were dying. Official data pointed to annual death tolls of tens of thousands of dolphins, whales and seals. Up to 750,000 seabirds, as well as millions of fish and sharks were caught and killed.
In response to the danger the United Nations General Assembly moved swiftly to ban large-scale driftnets on the high seas where no regulations existed to control this indiscriminate and destructive fishing technique. Despite the ban, the "walls of death" are still being set in many areas, both on the high seas and in some national waters.
A timeless seafaring symbol, immortalized in Coleridge's Rime of the Ancient Mariner, albatrosses roam widely across vast expanses of the oceans of the world, rarely coming ashore except to breed on remote oceanic islands in or near the Southern Ocean. Unfortunately for the various species of albatross in this remote part of the world, fleets of hundreds of fishing vessels from Japan, Korea, Taiwan and Indonesia hunt the prized southern bluefin tuna.
Albatross and other seabird species are caught and dragged underwater to their deaths on these deadly, baited hooks as they are launched from the ships. As many as 100 million hooks a year have been set by the Japanese fleet in the southern bluefin tuna fishery, for instance, so it is not surprising that tens of thousands of birds are being killed annually. One conservative calculation for albatross killed on Japanese longliners is 44,000 per year. The actual figure could be double that, according to researchers, but data on albatross kills by other nations' fishing vessels are not available. Twelve of the world's 14 albatross species are believed to be dying in their tens of thousands each year in this way. Because of the large number of birds affected, commercial fishing has been identified as the most serious threat to the survival of most albatross species.
Species of sea turtles are other hapless victims of incidental capture in fishing gear. Twenty thousand loggerhead turtles are captured every year by the Spanish longline fishery in the Mediterranean Sea, and four thousand of them are believed to die because they are returned to the sea with the hook still embedded in the throat.
In shrimp trawl fisheries off the southern United States the issue of marine turtle bycatch came to wide public attention relatively recently, largely because of the estimated 48,000 sea turtles caught annually by shrimp fishermen. The US National Marine Fisheries Service estimates that more than 11,000 of these were dying annually. Only after intense pressure from environmental groups was remedial action taken to modify trawl nets to exclude turtles from the catch. It remains to be seen just how effective these efforts will be.
If the current levels of fishing effort are not reduced, the impacts on marine animals such as dolphins, seabirds and sea turtles will increase unless governments act swiftly. First, by dramatically reducing the level of fishing effort so that there are far fewer vessels with the capacity to take too many fish. Second, by ensuring that fishing gear and practices responsible for this unnecessary carnage are either made safe or abandoned in favour of methods that avoid deadly interactions and thus spare threatened species of marine wildlife from extinction.
