Fish Wars: How cheap oil drives industrial longline fishing

by Robert Ovetz, PhD

ome fish is rich in essential oils such as highly touted omega 3s. But if tuna and swordfish are on your plate they are rich in another kind of oil-cheap petroleum harvested by war and occupation. One of the world's biggest beneficiaries of cheap oil is industrial longline fishing which is pillaging our fragile ocean ecosystem in the hunt for these two predatory fish.

    A groundbreaking new study by professor Peter Tyedmers of Canada's Dalhousie University soon to be published in The Encyclopedia of Energy explores the energy efficiency of a number of world fisheries, including longlining. Taking into account the material and petroleum required to power a wide variety of industrial fishing vessels, Tyedmers compares the amount of edible protein in their catch.

    The results are shocking. According to Tyedmers, amongst fisheries targeting high value species, “it is now common for direct fossil fuel energy inputs alone to exceed nutritional energy embodied in the catch by at least an order of magnitude.” In an earlier preliminary study of 54 North Atlantic fisheries from 5 countries, Tyedmers uncovered a wasteful paradox: “the availability of abundant energy... enables most contemporary fisheries to continue even when stocks are in decline.”

    Among the fisheries with the most inefficient “edible protein return on investment,” vessels targeting shrimp, tuna and swordfish are at the top of the list. By comparison, the most efficient fish species to target are small deep sea species such as menhaden and mackerel, most of which are unfortunately ground up into meal or used for oil.

    Tuna and swordfish are especially petroleum hungry fisheries, consuming three times the average energy in his study. Between 1986 and 1999, the amount of energy consumed by these fisheries skyrocketed fourfold.

    Replicating the results of an earlier study in Japan, Tyedmers puts longlining at the very bottom in terms of efficiency. Since the mid 1970s oil crisis, the amount of fuel consumed by larger and larger vessels has been rapidly outpacing the growth in the actual catch.

    Tyedmers' study identifies a new problem associated with targeting large predatory species such as tuna and swordfish, adding to an already lengthy and damning list. These fish are caught by so-called “longlines” which can stretch up to 50 miles long and carry hundreds of baited hooks. Longlining creates a nonselective killing field that annually cruelly snags and drowns upwards of 4 million endangered whales, dolphins, sea turtles, porpoises, sharks, seabirds, sea lions, and billfish such as marlins in the Pacific alone.

    The Pacific leatherback sea turtle has been the hardest hit by longlining. The leatherback's female nesting population has collapsed by 95% in the past 22 years. This sea turtle is expected to go extinct within the next few decades unless action to reduce the mortality of adult turtles is taken.

    Not only is longlining for tuna and swordfish deadly for sea turtles, but it is dangerous to humans. These two predatory species contain high levels of methylmercury, which is dangerous to developing fetuses, pregnant and nursing women, children and the elderly. Both the US Food and Drug

    Administration and Environmental Protection Agency have issued warnings about mercury in these species and California requires a warning be displayed in supermarkets.

    A study by two of Tyedmers' colleagues at Dalhousie University published in the journal Nature in 2003 found that about 90% of our predatory fisheries are already depleted. This is having a dire multiplier effect on the very fisheries upon which 1 billion people depend for their primary source of animal protein. The massive expansion of industrial fishing capacity powered by “cheap” oil is at the heart of the crisis.

    If it weren't enough that longline fishing is extremely inefficient, and kills leatherback sea turtles and other endangered marine species, it is also a major contributor of climate warming carbon dioxide gases. The fisheries in Tyedmers' study consumed a staggering 1 billion liters of diesel fuel, each liter of fuel producing 2.66 kilograms of CO2. The impact of global warming on the ocean ecosystem is devastating. Water temperatures are rising and microorganisms at the base of the ocean food chain are in decline.

    Fish may be highly valued for its essential oils but this is the kind of oil we would be better off leaving off our plates. Robert Ovetz, PhD is a Marine Species Campaigner with the Sea Turtle Restoration Project. Contact him at: robert@seaturtles.org. Sign their petition calling for a UN moratorium on Pacific longlining at: www.seaturtles.org.