Reconstructing ecosystem dynamics in the central Pacific Ocean, 1952-1998, 1: estimating population biomass and recruitment of tunas and billfishes

Commercial yield of tunas in the central Pacific increased severalfold between 1952 and 1998. Age-structured production models that incorporate information from multiple fisheries to estimate population biomass and recruitment trends of tunas (Thunnus alalunga, Thunnus albacares, Thunnus obesus, and...

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Bibliographic Details
Published in:Canadian journal of fisheries and aquatic sciences 2002-11, Vol.59 (11), p.1724-1735
Main Authors: Cox, Sean P, Walters, Carl J, Kitchell, James F, Essington, Timothy E, Boggs, Christofer, Kaplan, Isaac
Format: Article
Language:English
Subjects:
Biomass
Ecosystem dynamics
Euthynnus pelamis
Makaira nigricans
Marine
Marine ecosystems
Martell, Steven J
Supply
Thunnus albacares
Thunnus obesus
Tuna
Xiphias gladius
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Summary:Commercial yield of tunas in the central Pacific increased severalfold between 1952 and 1998. Age-structured production models that incorporate information from multiple fisheries to estimate population biomass and recruitment trends of tunas (Thunnus alalunga, Thunnus albacares, Thunnus obesus, and Katsuwonus pelamis) and billfish were developed in the central north Pacific. The results suggest that all tuna stocks remain above 40% of 1950s levels, whereas blue marlin (Makaira nigricans) declined to 21% and swordfish (Xiphias gladius) to 56%. Estimated biomasses of juvenile bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tuna increased to 112 and 129%, respectively, of 1950s levels. Juvenile albacore (Thunnus alalunga) decreased during the 1970s and 1980s but recovered to historical highs (121%) in recent years. Skipjack (Katsuwonus pleamis) remained relatively stable between 1952 and 1980, declined by 35% between 1981 and 1990, and then increased to 68% of 1950s levels. These changes generally represent decreases in top predators and increases in small tunas, which make up their prey. Application of stock assessment methods set in a food web context provides an important step toward developing a method that recognizes fishery exploitation as a component of ecosystem dynamics.
ISSN:0706-652X
1205-7533