Cetacean Interactions with Trawls: A Preliminary Review

Abstract

Cetaceans interact with trawls to an undetermined extent. A preliminary review of global data indicates that individuals of 25 cetacean species (two mysticete, 23 odontocete) have been documented to have died in working trawls or discarded trawling gear. Cetacean interactions with trawls are complex, in part because both fishermen and cetaceans are drawn to areas of high prey density. Furthermore, within such areas, cetaceans are probably often attracted to trawling activities because they make it easier for the animals to exploit a concentrated food source. Individuals of 15 (possibly 16) cetacean species (13 odontocete, and one or even two mysticete) have been reported to feed in association with trawls. Animals follow working nets (feeding on stirred-up organisms or fish gilled in mesh) and also feed on discarded by-catch. Damage to gear as a result of feeding interactions or entanglement has been reported. Such damage results in (1) harm to the animals, (2) creation of negative opinions of cetaceans by fishermen (regardless of whether a cetacean or a shark is, in fact, responsible for the damage in question), and (3) loss of time and money for repair and replacement of gear. The relationships of cetaceans with trawls need to be further studied to determine what effects the trawl fisheries have on the ecology and population status of the whales and dolphins involved.