Results of a short study of interactions of cetaceans and longline fisheries in Atlantic waters: environmental correlates of catches and depredation events

Gema Hernandez-Milian, Sabine Goetz, Catuxa Varela-Dopico, Jose Rodriguez-Gutierrez, Jorge Romon-Olea, Jose R. Fuertes-Gamundi, Edelmiro Ulloa-Alonso, Nick J. C. Tregenza, Andy Smerdon, Monserrat G. Otero, Vicente Tato, Jianjun Wang, M. Begona Santos, Alfredo Lopez, Rebeca Lago, Julio M. Portela, Graham J. Pierce

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32 Citations (Scopus)


In the Atlantic, economic losses have been reported from shark, swordfish and tuna longline fisheries due to depredation by cetaceans. We examined interactions of odontocete cetaceans with commercial longliners operating in waters off Brazil and the Azores archipelago during 2006-2007, analysing relationships between catches, depredation on hooked fish, cetacean sightings, acoustic records of cetacean presence and environmental variables. Data were provided by skippers of six vessels and by on-board observers for two vessels. The percentage of longline sets depredated by cetaceans was low (ranging from 1% to 9% of total sets per ship) but the proportion of fish damaged was high (up to 100%) when depredation occurred. Catches were related to the phase of the moon, cloud cover, sea surface temperature and water depth whereas cetacean sightings were primarily related to catches. In particular there was a positive association between Delphinus delphis sightings and catches of swordfish, and between Stenella frontalis sightings and mako catches. Acoustic detection was low when depredation by false killer whales occurred although high rates of clicks were detected when delphinids were sighted and false killer whales were by-caught. This may indicate that false killer whales are not echolocating when feeding on fish hooked on a longline.

Original languageEnglish
Pages (from-to)251-268
Number of pages18
Issue number1
Early online date1 Aug 2008
Publication statusPublished - Oct 2008


  • cetaceans
  • false killer whale
  • longline fishery
  • depredation
  • hydrophones
  • behaviour
  • habitat modelling
  • bottle-nosed dolphins
  • ultrasonic telemetry
  • pseudorca-crassidens
  • pelagic longlines
  • swordfish fishery
  • sea-turtles
  • T-pods
  • tuna
  • echolocation
  • Southern

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