Length-based growth, maturity and natural mortality of the cockfish Callorhinchus callorhynchus (Linnaeus, 1758) off Coquimbo, Chile

Abstract

The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history parameters for cockfish Callorhinchus callorhynchus (Holocephali-Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between 20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic length L ∞ =52 cm SL, growth coefficient K=0.473 yr −1 , and age at length zero t 0 =−0.690 yrs. For females the best model was represented by 10 age-classes (L ∞ =70.3 cm SL, K=0.193 yr −1 , t 0 =−1.158 yrs) in the lengthfrequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr −1 for males and between 0.12 and 0.37 yr −1 for females, depending upon the method used. It is concluded that C. callorhynchus is a species with lifehistory parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.

Reproductive biology of the cockfish, Callorhinchus callorynchus (Chondrichthyes: Callorhinchidae), in coastal waters of the northern Argentinean Sea

“…The PCL 50 estimated for females in this study (466.22 mm; n=167) was similar to that recently obtained in northern Patagonian waters (474.80 mm; n=398) (Bernasconi et al, 2015b) but smaller than those previously reported in that zone (490 mm; n=123) (Di Giácomo, Perier, 1994) and in Chilean waters (500 mm; n=40) (Alarcón et al, 2011). These differences may be attributable to differences in the methods for assessing maturity and/or in sample size used in each study.…”

“…Sexual size dimorphism is also a common characteristic observed in other holocephalans, with females larger than males (Freer, Griffiths, 1993;Francis, 1997;Nibam, 2011;Bell, 2012). The same pattern was observed for C. callorynchus in northern Patagonian waters (PCL males=620 mm; PCL females=760 mm) and in Chilean waters (PCL males=620 mm; PCL females=700 mm) (Di Giácomo, 1992;Alarcón et al, 2011;Bernasconi et al, 2015b). The differences in maximum size among studies for males (present study: n=19; northern Patagonian waters: n=147; Chilean waters: n=193) and females (present study: n=167; northern Patagonia waters: n =1571; Chilean waters: n=209) may result from differences in sample sizes.…”

“…However, PCL-TM relationships for both sexes of this species showed negative allometry in northern Patagonian waters and positive allometry (b > 3) in Chilean waters (Di Giácomo, 1992;Alarcón et al, 2011). These differences result from the fact that within species the variance in weight-length relationships can be substantial, depending on the season, population, and annual or regional differences in environmental conditions (Froese, 2006).…”

“…Moreover, the bias in maximum size observed among studies may be explained by sampling depth variations. Samples of specimens in Chilean waters were taken in coastal waters (<30 m depths) as in the present study, but in northern Patagonian waters samples were taken at depths from 20 to 190 m where individuals of C. callorynchus were segregated by size, with larger individuals at depths >50 m (Di Giácomo, 1992;Alarcón et al, 2011;Bernasconi et al, 2015b). For this reason, the frequency size distribution of C. callorynchus at depths >50 m should be analyzed in waters of south-eastern Buenos Aires Province.…”

“…reproductive cycles, size at maturity, fecundity, nursery grounds and habitat) is necessary to develop stock assessment models and ecological risk assessment in order to implement effective sustainable management practices (Bonfil, 2005). Despite its fishery importance and the wide distribution of C. callorynchus off southern South America, its life-history characteristics were studied only in northern Patagonian waters off Argentina (41º-42º S 64º-65º W) (Di Giácomo, 1990Giácomo, , 1992Di Giácomo, Perier, 1994, 1996Bernasconi et al, 2015aBernasconi et al, , 2015b and in coastal waters off Coquimbo (30º15'S 70º30'W), Chile (Alarcón et al, 2011). In addition, the Argentinean port with the highest landings of chondrichthyans is located in the south-eastern Buenos Aires Province (Mar del Plata: 38º01'S 57º31'W), where the abundance of C. callorynchus was reduced by nearly 50% from 1994 to 1999 (Massa et al, 2004;Consejo Federal Pesquero, 2009).…”