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Marine Ecology Progress Series

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MEPS 347:111-119 (2007)  -  DOI:

Killer whale predation on bluefin tuna: exploring the hypothesis of the endurance-exhaustion technique

C. Guinet1,*, P. Domenici2,3, R. de Stephanis4, L. Barrett-Lennard5, J. K. B. Ford6, P. Verborgh1,4

1CEBC-CNRS, 79 360 Villiers en Bois, France
2IAMC-CNR, and 3International Marine Centre, Località Sa Mardini,Torregrande (Or) 09072 Italy
4CIRCé, C/Cabeza de Manzaneda 3, Algeciras-Pelayo, 11390 Cadiz, Spain
5Vancouver Aquarium Marine Science Centre, Box 3232, Vancouver, British Columbia V6B 3X8, Canada
6Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, British Columbia V9T 6N7, Canada

ABSTRACT: Killer whales Orcinus orca occur in the area of the Strait of Gibraltar, where they prey on migrating bluefin tuna Thunnus thynnus. In the spring, killer whales were observed to chase tuna for up to 30 min at a relatively high sustained speed (3.7 ± 0.2 m s–1) until they captured them. Using simple models based on previous locomotor performance data on killer whales and thunnids, we investigated the hypothesis that killer whales push tuna beyond their aerobic limits to exhaust and capture them. To test this hypothesis, the endurance of bluefin tuna was estimated from data on maximum burst and aerobic swimming available for bluefin and yellowfin tuna T. albacares. The endurance performance of killer whales was evaluated on the basis of the maximal rate of oxygen uptake during exercise (VO2max). We modelled the maximum aerobic power output for a killer whale according to swimming speed using a VO2max ranging between 20 and 30 ml O2 kg–1 min–1. The output of this model was compared to the observed sustained swimming speed of killer whales chasing prey over long durations. Our results support the hypothesis that killer whales may use an endurance-exhaustion technique to catch small to medium sized (up to 0.8 to 1.5 m) bluefin tuna, while larger tuna may be inaccessible to killer whales unless they use cooperative hunting techniques or benefit through depredation of fish caught on long lines, drop lines or trap nets.

KEY WORDS: Killer whales · Bluefin tuna · Predation · Endurance · Swimming speed

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Cite this article as: Guinet C, Domenici P, de Stephanis R, Barrett-Lennard L, Ford JKB, Verborgh P (2007) Killer whale predation on bluefin tuna: exploring the hypothesis of the endurance-exhaustion technique. Mar Ecol Prog Ser 347:111-119.

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