Results of a short study of interactions of cetaceans and longline fisheries in Atlantic waters: environmental correlates of catches and depredation events |
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Authors: | Gema Hernandez-Milian Sabine Goetz Catuxa Varela-Dopico José Rodriguez-Gutierrez Jorge Romón-Olea José R Fuertes-Gamundi Edelmiro Ulloa-Alonso Nick J C Tregenza Andy Smerdon Monserrat G Otero Vicente Tato Jianjun Wang M Begoña Santos Alfredo López Rebeca Lago Julio M Portela Graham J Pierce |
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Institution: | 1. University of Aberdeen, Tillidrone Avenue, Aberdeen, AB24 2TZ, UK 2. Instituto Espa?ol de Oceanografía, Centro Oceanográfico de Vigo, Cabo Estai, Canido, 36200, Vigo, Spain 3. Estación de Biología Mari?a da Gra?a, University of Santiago de Compostela, Casa do Hórreo e Casa da Estrela, Rúa da Ribeira 1-4, A Gra?a, 15590, Ferrol, Spain 4. Cooperativa de Armadores de Pesca del Puerto de Vigo, Sociedad Coop. Ltda., Puerto Pesquero, Edif. Cooperativa de Armadores, Apdo. 1078, 36202, Vigo, Spain 5. Chelonia Limited, Beach Cottage, 5 Beach Terrace, Long Rock, Cornwall, TR20 8JE, UK 6. Aquatec Group Ltd., High Street, Hartley Wintney, Hampshire, RG27 8NY, UK 7. MG Otero Consultores SL, Porto Pesqueiro, Nvo Tinglado Xeral Empaque Of. 8, PO Box?1132, 36202, Vigo, Spain 8. CEMMA, Apdo. 15, 36380, Gondomar, Pontevedra, Spain
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Abstract: | 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.
Guest editor: V. D. Valavanis
Essential Fish Habitat Mapping in the Mediterranean |
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Keywords: | Cetaceans False killer whale Longline fishery Depredation Hydrophones Behaviour Habitat modelling |
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