title: Bioenergetics, Trophic Ecology, and Niche Separation of Tunas.
abstract: Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts.
authors: Inter-American Tropical Tuna Commission, La Jolla, CA, United States. Electronic address: rolson@iattc.org.
authors: R J
authors: RJ
authors: Olson
authors: CSIRO Marine and Atmospheric Research, Hobart, TAS, Australia.
authors: J W
authors: JW
authors: Young
authors: Institut de Recherche pour le Développement (IRD), Mediterranean Institute of Oceanography (Aix-Marseille Université, CNRS, IRD, Université de Toulon), Marseille, France.
authors: F
authors: F
authors: Ménard
authors: IRD, UMR MARBEC (IRD, UM, Ifremer, CNRS), Sète cedex, France.
authors: M
authors: M
authors: Potier
authors: Pacific Community (SPC), Nouméa cedex, New Caledonia.
authors: V
authors: V
authors: Allain
authors: AZTI-Tecnalia/Marine Research, Pasaia, Gipuzkoa, Spain.
authors: N
authors: N
authors: Goñi
authors: Massachusetts Division of Marine Fisheries, New Bedford, MA, United States.
authors: J M
authors: JM
authors: Logan
authors: Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico.
authors: F
authors: F
authors: Galván-Magaña
mesh_terms: D000818:Animals; D004032:Diet / Q000662:veterinary*; D004435:Eating; D004463:Ecology; D004734:Energy Metabolism / Q000502:physiology; D005247:Feeding Behavior; D005398:Fisheries / Q000191:economics; D008954:Models, Biological; D009792:Oceans and Seas; D012098:Reproduction / Q000502:physiology; D014413:Tuna / Q000378:metabolism / Q000502:physiology*
keywords: Bioenergetics; Climate change; Food webs; Niche separation; Pelagic; Predator–prey; Stable isotope ecology; Trophic ecology; Tunas