Age and Growth of the Skipjack Tuna Katsuwonus pelamis in the Western and Central Pacific Ocean

Abstract

The age and growth of the skipjack tuna Katsuwonus pelamis were determined using otoliths sampled from a Korean tuna purse seine fishery in the Western and Central Pacific Ocean from January 2005 to September 2006. A total of 312 otoliths were used to estimate the ages of skipjack tuna, which ranged from 1 to 7 years. The relationships between otolith ring radius (R) and fork length (FL) for female, male, and sex combined were FL = 19.74R + 1.50 ( $r^2=0.54$), FL = 17.66R + 6.35 ( $r^2=0.47$), and FL = 18.83R + 3.36 ( $r^2=0.53$), respectively. The back-calculated fork lengths of each age ( $FL_{year}$) were $FL_1=36.2cm$, $FL_2=43.3cm$, $FL_3=48.3cm$, $FL_4=52.6cm$, $FL_5=56.5cm$, $FL_6=60.8cm$, and $FL_7=63.2cm$. The relationships between fork length (FL) and total weight (TW) for female, male, and sex combined were $TW=0.00001FL^{3.19}(r^2=0.95)$, $TW=0.00001FL^{3.17}(r^2=0.95)$, and $TW=0.000009FL^{3.23}(r^2=0.95)$, respectively. The von Bertalanffy growth parameters of skipjack tuna estimated in this study were $L_{\infty}=77.4cm$, K = 0.176/year, and $t_0=-2.569years$.