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1 October 2015 Influence of Central Pacific Oceanographic Conditions on the Potential Vertical Habitat of Four Tropical Tuna Species
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Abstract

Climate change has resulted in the geographic and vertical expansion of oxygen minimum zones but their impact on the vertical distribution of commercially important species, such as tunas, is not well understood. Although La Niña events are characterized by increased upwelling along the equator, the increased primary productivity and bacterial proliferation drive the expansion of oxygen minimum zones. Vertical habitat of four tropical tuna species were characterized using direct observations of the oceanographic conditions of the Central Pacific Ocean during the 2008 La Niña event and existing primary literature on temperature and dissolved oxygen physiological tolerances for these tunas. Concentrations of potential prey were estimated using Acoustic Doppler Current Profiler raw backscatter and surface zooplankton tows. Based on the oceanographic conditions observed from February to June, low dissolved oxygen levels, more so than low temperatures, were inferred to restrict the predicted vertical habitat of four commercially important tuna species (bigeye, yellowfin, skipjack, and albacore). During peak La Niña conditions, temperature and dissolved oxygen tolerance limits of all four tuna species were reached at approximately 200m. Zooplankton and myctophid fish densities peaked in the upper 200m between 0° N and 5° N, which corresponded to a region with a shallow thermocline (150 m). Our findings suggest the possibility that competition and susceptibility to surface fishing gears may be increased for tropical tunas during a strong La Niña event due to vertical habitat restrictions.

©2015 by University of Hawai‘i Press All rights reserved
Alison L. Deary, Skye Moret-Ferguson, Mary Engels, Erik Zettler, Gary Jaroslow, and Gorka Sancho "Influence of Central Pacific Oceanographic Conditions on the Potential Vertical Habitat of Four Tropical Tuna Species," Pacific Science 69(4), 461-475, (1 October 2015). https://doi.org/10.2984/69.4.3
Accepted: 1 February 2015; Published: 1 October 2015
JOURNAL ARTICLE
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