Bycatch trends Cetacean bycatch

a dall s porpoise caught in fishing net

generally cetacean bycatch on increase. of world’s cetacean bycatch occurs in gillnet fisheries. mean annual bycatch in u.s. alone 1990–1999 6,215 marine mammals, dolphins , porpoises being primary cetaceans caught in gillnets. study read et al. estimated global bycatch through observation of u.s. fisheries , came conclusion annual estimate of 653,365 marine mammals, comprising 307,753 cetaceans , 345,611 pinnipeds caught 1990–1994.

while gillweed nets principal concern, other types of nets pose problem: trawl nets, purse seines, beach seines, longline gear, , driftnets. driftnets known high rates of bycatch , affect cetaceans , other marine species. fatal small toothed whales (odontocetes) , sperm whales, other marine mammals , fish such sharks, sea birds , sea turtles. many fisheries routinely use driftnets exceeding eu size limit of 2.5 km/boat. illegal drift-netting major issue, in important feeding , breeding grounds cetaceans.

however, tuna industry has achieved successes in reversing cetacean bycatch trends. international recognition of problem of cetacean bycatch in tuna fishing led agreement on international dolphin conservation program in 1999 , overall there has been dramatic reduction in death rates. in particular, dolphin bycatch in tuna fishing in east tropical pacific has dropped 500,000 per year in 1970 100,000 per year in 1990 3,000 per year in 1999 1,000 per year in 2006.