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

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 t₀ = ‑0.690 yrs. For females the best model was represented by 10 age-classes (L_∞ = 70.3 cm SL, K = 0.193 yr^‑1, t₀ = ‑1.158 yrs) in the length-frequency 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 life-history parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.