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Marine Ecology Progress Series

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MEPS 458:283-302 (2012)  -  DOI:

Pelagic predator associations: tuna and dolphins in the eastern tropical Pacific Ocean

Michael D. Scott1,*, Susan J. Chivers2, Robert J. Olson1, Paul C. Fiedler2, Kim Holland3

1Inter-American Tropical Tuna Commission, 8604 La Jolla Shores Dr., La Jolla California 92037, USA
2Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 3333 North Torrey Pines Court, La Jolla, California 92037, USA
3Hawaii Institute of Marine Biology, University of Hawaii at Manoa, PO Box 1346, Coconut Island, Kaneohe, Hawaii 96744, USA

ABSTRACT: The association of yellowfin tuna and pantropical spotted dolphins in the eastern tropical Pacific Ocean (ETP) has been exploited by tuna fishermen and has intrigued scientists for decades, yet we still have questions about what the benefits of the association are—whether the association is obligatory or facultative, why the tuna are most often found with spotted dolphins, and why the species associate most strongly in the ETP. We review the hypotheses that have been proposed to explain the bond and present results from 3 studies conducted to address these hypotheses: a simultaneous tracking study of spotted dolphins and yellowfin tuna, a trophic interactions study comparing their prey and daily foraging patterns, and a spatial study of oceanographic features correlated with the tuna–dolphin association. These studies demonstrate that the association is neither permanent nor obligatory and that the benefits of the association are not based on feeding advantages. These studies do support the hypothesis that one or both species reduce the risk of predation by forming large, mixed-species groups. The association is most prevalent where the habitat of the tuna is compressed to the warm, shallow, surface waters of the mixed layer by the oxygen minimum zone, a thick layer of oxygen-poor waters underlying the mixed layer. The association has been observed in other oceans with similar oceanographic conditions, but it is most prevalent and consistent in the ETP, where the oxygen minimum zone is the most hypoxic and extensive in the world.

KEY WORDS: Spotted dolphin · Yellowfin tuna · Tuna–dolphin bond · Spinner dolphin · ETP · Purse-seine fishery · Food habits · Tagging

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Cite this article as: Scott MD, Chivers SJ, Olson RJ, Fiedler PC, Holland K (2012) Pelagic predator associations: tuna and dolphins in the eastern tropical Pacific Ocean. Mar Ecol Prog Ser 458:283-302.

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