The Net Effect? A review of cetacean bycatch in pelagic trawls and other fisheries in the north-east Atlantic

The incidental capture, or bycatch, of non-target species such as mammals, birds, turtles, fish and other marine species in fisheries is recognised to be a major problem in many parts of the world. It has been estimated that 23% of the global fisheries catch is thrown back into the sea dead and wasted. Globally, the toll on all cetaceans (whales, dolphins and porpoises) is estimated to exceed 300,000 animals each year and bycatch is acknowledged to be a serious threat to the conservation of cetaceans in the northeast Atlantic region. However, despite evidence of thousands of dolphins and porpoises being killed each year in a variety of fisheries in this region, some at clearly unsus-tainable levels, there has been remarkably little policy or practical response to the issue at either national or EU level. The cetacean species caught in the greatest numbers in the northeast Atlantic are the common dolphin and the harbour porpoise. High levels of common dolphin bycatch have been recorded in pelagic trawl fisheries such as the UK sea bass pair trawl fishery and the Irish albacore pair trawl fishery, but the limited monitoring of pelagic fisheries to date precludes an assessment of total mortality levels. However, the number and scale of pelagic trawl fisheries operating in the Celtic Sea, Biscay and Channel area, which also include large French, Dutch and Danish fleets, coupled with the number of bycaught dolphins that strand on surrounding coasts, indicate that the total annual mortality figure is in the thousands, possibly many thousands , and is probably unsustainable. Other species caught include Atlantic white-sided dolphins, striped dolphins, long-finned pilot whales, and bottlenose dolphins. The conservation implications for these species are difficult to assess, but they may also be a cause for major concern. The harbour porpoise is killed in high numbers in bottom-set gillnet fisheries. Observer monitoring in some areas has recorded large and unsustainable bycatch levels: some 2,200 porpoises per year in the Celtic Sea and around 8,000 per year in the North Sea. In the Baltic Sea, where the harbour porpoise population is extremely low, and affected by both bottom-set nets and driftnets, even a very low level of bycatch is critical in conservation terms. Given all the major areas of uncertainty, it is vital that extreme precaution is applied in assessing the significance of cetacean bycatch and, in particular, in defining conservation and management objectives. It is recommended …