Age, growth and mortality of Pontinus kuhlii (Bowdich, 1825) (Scorpaeniformes: Scorpaenidae) in the Gorringe, Ampère, Unicorn and Lion seamounts

Abstract

Age and growth of Pontinus kuhlii were studied using otoliths of 153 males and 148 females, with males having a greater length (and age) than females. A high level of agreement was achieved among readers. Due to gear selectivity, only ages above 7 years (males) and 8 years (females) were estimated in whole otoliths. To estimate length-at-age in younger specimens, backcalculation was also considered but its use in otoliths with ages greater than 22 years was not possible because the growth rings were too close to each other. Von Bertalanffy growth parameters were estimated by sex using each of these methods and also using an approach that combines mean length-at-age obtained from backcalculation and direct reading on the otoliths. The likelihood ratio test showed significant differences between sexes in the three approaches and Akaike's information criterion suggests that the backcalculation approach was the best one for describing P. kuhlii growth: TL=38.89[1e(0.07(t+1.96))] and TL=56.50[1-e(-0.04(t+1.87))] for females and males, respectively. Natural mortality estimates varied around 0.15 year-1 and 0.07 year-1 for females and males, while the total mortality estimated for 2011 was 0.33 year-1 for females and 0.21 year-1 for males.