Age and growth estimation of bigeye tuna, Thunnus obesus (Teleostei: Scombridae) in the southwestern Atlantic

Paulo Duarte-Neto,Rosangela P Lessa,Fábio M Higa

doi:10.1590/s1679-62252012000100014

Paulo Duarte-Neto, Rosangela P Lessa + Show 1 more

Open Access

https://doi.org/10.1590/s1679-62252012000100014

Copy DOI

Abstract

The purpose of the current study was to supply the first information on age and growth for Thunnus obesus caught in the equatorial south-western Atlantic using dorsal spines, an approach that has been successfully employed for ageing tuna species. The study was conducted using a multi-model inference based on information theory for back-calculated and observed length-at-age data. Uncertainty associated with the parameter estimation was verified and results were compared to other accounts on the species, considering both the statistical and methodological contexts. Samples were collected in Natal city (Rio Grande do Norte State, Brazil) from February 1999 to January 2000, of tuna vessels and from surveys, aimed at providing information on the Brazilian Exclusive Economic Zone (EEZ) in the area around São Pedro and São Paulo Archipelago. Validation using marginal increment indicated that one ring is deposited per year. Mean length-at-age ranged of 54.3 to 177.5 cm (fork length) for ages 1 to 9 years. Von Bertalanffy, Richards, and Gompertz models were considered suitable for the bigeye tuna. Hence, the model-averaged asymptotic length ¯L∞ was estimated. The averaged model generated in the present study by back-calculation was considered appropriate for describing the growth of T. obesus.

Highlights

The bigeye tuna, Thunnus obesus (Lowe, 1839), has ubiquitous distribution across all oceans between 45o N and 40o S, attaining up to 230 cm in length and 250 kg in weight (Collette & Nauen, 1983; Cayré et al, 1993)
Age and growth estimation of Thunnus obesus recapture information (Chow et al, 2000; Durand et al, 2005; ICCAT, 2005; Gonzalez et al, 2008), it is accepted that this species composes a unique stock in the Atlantic Ocean, with varying environmental factors across the distribution area contributing to differences in population parameters
In Brazil, the species is not targeted by any local fleets and the little information available comes from the by-catch of vessels targeting tuna and swordfish in the Brazilian Exclusive Economic Zone (EEZ), including the area around São Pedro and São Paulo Archipelago (Vaske-Jr. et al, 2004)

Summary

Introduction

The bigeye tuna, Thunnus obesus (Lowe, 1839), has ubiquitous distribution across all oceans between 45o N and 40o S, attaining up to 230 cm in length and 250 kg in weight (Collette & Nauen, 1983; Cayré et al, 1993). It is a commercially important species of tuna inhabiting the warm waters of the Atlantic, Indian, and Pacific Oceans, highly prized and one of the most valuable species for the Asian market, where it is consumed fresh as sashimi (Hanamoto, 1987; Sun et al, 2001). The bigeye tuna was abundantly recorded in experimental fisheries carried out from 2000 to 2002 in the area from 02 to 05o N, where the CPUE was 22 Kg/100 hooks, composing 38.7 % of the overall tuna catch (Asano-Filho et al, 2004)

Objectives

Methods

Findings

Conclusion