Title Estimating the impact of depredation by killer whales and sperm whales on longline fishing for toothfish (Dissostichus eleginoides) around South Georgia
Author Clark, J.M.; Agnew, D.J.
Author Affil Clark, J.M., MRAG, Marine Resources and Fisheries Consultants, London, United Kingdom. Other: Imperial College London, United Kingdom
Source CCAMLR Science, Vol.17, p.163-178. Publisher: Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), International. ISSN: 1023- 4063
Publication Date 2010
Notes In English GeoRef Acc. No: 309659
Index Terms Atlantic Ocean--South Atlantic; Atlantic Ocean Islands--South Georgia; Southern Ocean; Atlantic Ocean; Atlantic Ocean Islands; behavior; Cetacea; Chordata; Delphinidae; environmental effects; Eutheria; feeding; fisheries; human activity; Mammalia; migration; movement; Orcinus orca; Physeter macrocephalus; Physeteridae; predation; Scotia Sea Islands; seasonal variations; South Atlantic; South Georgia; Tetrapoda; Theria; Vertebrata
Abstract Analysis of observer data on longline fishing vessels in waters around South Georgia between 2003-09 shows that cetaceans were observed on 22% of lines, with killer whales (Orcinus orca) present on 3.8% and sperm whales (Physeter macrocephalus) on 17.7%. Killer whales in pods of 4-10 animals appear to actively seek out fishing vessels and strip line of large number of toothfish, depressing catch per unit effort (CPUE) by about 50%. Sperm whales in pods of 1-4 animals depress CPUE by less than 20%. Killer whale encounters and pod sizes have remained constant in recent years with no obvious seasonal pattern, but sperm whales have been encountered more frequently and in larger pods, with most interactions occurring during May and becoming fewer towards end of season in August. Both species demonstrate east to west migration throughout season unrelated to pattern of fishing effort. Estimated amounts of toothfish removed from longlines by cetaceans vary between 1% and 8% of declared catches between 2003-09, with average of 3.6%.
Publication Type journal article
Record ID 91397