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Increases in the Relative Abundance of Mid-Trophic Level Fishes Concurrent with Declines in Apex Predators in the Subtropical North Pacific, 1996–2006

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Type: Journal Article
Author: Polovina, Jeffrey J.; Abecassis, Melanie; Howell, Evan A.; Woodworth, Phoebe
Journal: Fisheries Bulletin
Volume: 107
Page(s): 523-531
Date: 2009
URI: https://hdl.handle.net/10535/6777
Sector: Fisheries
Region: North America
Subject(s): fisheries
climate change
Abstract: "Catch rates for the 13 most abundant species caught in the deep-set Hawaii-based longline fishery over the past decade (1996–2006) provide evidence of a change among the top North Pacific subtropical predators. Catch rates for apex predators such as blue shark (Prionace glauca), bigeye (Thunnus obesus) and albacore (Thunnus alalunga) tunas, shortbill spearfish (Tetrapturus angustirostris), and striped marlin (Tetrapturus audax) declined by 3% to 9% per year and catch rates for four midtrophic species, mahimahi (Coryphaena hippurus), sickle pomfret (Taractichthys steindachneri), escolar (Lepidocybium flavobrunneum), and snake mackerel (Gempylus serpens), increased by 6% to 18% per year. The mean trophic level of the catch for these 13 species declined 5%, from 3.85 to 3.66. A shift in the ecosystem to an increase in midtrophic-level, fast-growing and short-lived species is indicated by the decline in apex predators in the catch (from 70% to 40%) and the increase in species with production to biomass values of 1.0 or larger in the catch (from 20% to 40%). This altered ecosystem may exhibit more temporal variation in response to climate variability."

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