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

Abstract

SUMMARY: 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[1-e (-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.Keywords: Pontinus kuhlii, offshore rockfish, whole otoliths, precision estimators, age and growth, Scorpaenidae, mortality. RESUMEN: Edad, crEcimiEnto y mortalidad dE Pontinus kuhlii (Bowdich, 1825) (ScorpaEniformES: ScorpaEnidaE) En loS montES SuBmarinoS dE GorrinGE, ampèrE, unicorn y lion. -La edad y crecimiento de Pontinus kuhlii se ha estudiado a partir de otolitos de 153 machos y 148 hembras, alcanzando los machos una talla mayor (y edad) que las hembras. Un alto nivel de acuerdo fue alcanzado entre los lectores. Debido a la selectividad del arte de pesca, sólo las edades de más de 7 años (machos) y 8 años (hembras) pudieron ser estimadas en otolitos enteros. Para la estimación de la talla por edad en los ejemplares más jóvenes, el retrocálculo también fue considerado, pero su uso en los otolitos con edades mayores de 22 años no fue posible, ya que los anillos de crecimiento se encontraban demasiado cerca unos de los otros. Los parámetros de crecimiento, ajustados a la ecuación de Von Bertalanffy, fueron estimados por sexo con ambos métodos, y también a partir de otro que combina la talla media por grupo de edad obtenida a partir del retrocálculo y de la lectura directa en los otolitos. La prueba de máxima verosimilitud mostró diferencias significativas entre sexos en los tres métodos y el criterio Akaike de información sugiere que el retrocálculo fue el mejor para describir el crecimiento de P. kuhlii: TL=38.89[1-e (-0.07(t+1.96)) ] y TL=56.50[1-e (-0.04(t+1.87)) ] para las hembras y machos, respectivamente. La estimación de la mortalidad natural varió entre 0.15 año -1 y 0.07 año -1 para hembras y machos, mientras que la mortalidad total estimada para 2011 fue de 0.33 año -1 para las hembras y 0.21 año -1 para los machos.Palabras clave: Pontinus kuhlii, rasc...

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