A global review of porpoise ( Cetacea: Phocoenidae) mortality in gillnets

Abstract

A global review of mortality of porpoises in gillnet fisheries indicates that individuals of all six species become entangled and die in gillnets. Harbor porpoises Phocoena phocoena are taken throughout their range and several populations are in decline, at least partly as a result of gillnet entanglement. The vaquita P. sinus is the most endangered cetacean species, and gillnet fisheries in the northern Gulf of California, Mexico, threaten the single population with extinction. Burmeister's porpoises P. spinipinnis are taken in several gillnet fisheries in South America; populations in Peru appear to be most severely affected. In southern South America, spectacled porpoises Australophocaena dioptrica are known to be caught in gillnets, but the effects of these takes are unknown. Primarily in the western North Pacific, Dall's porpoises Phocoenoides dalli are entangled in driftnet fisheries in large numbers, but so far major impacts have not been apparent. Although taken in gillnets in many areas throughout the Indo-Pacific region, only those finless porpoise Neophocaena phocaenoides populations in China are considered to be threatened by gillnet catches. In most circumstances, existing information is insufficient to evaluate the effects of gillnets on porpoise v to be severe. Gillnets represent the single most important threat to porpoises as a group, and this may be an example of a ‘no technical solution problem’. We conclude that better documentation of catches and new approaches to dealing with porpoise/gillnet interaction problems are needed in order to prevent the loss of several species and populations.