Study of the growth of southern black and white monkfish stocks

Abstract

Growth parameters for black and white monkfish from ICES southern stocks, ICES Divisions VIIIc and IXa (Spanish and Portugese waters) were estimated from age readings of the first ray of the dorsal fin (illicia) sections and fitting the yon Bertalanffy growth model. Black monkfish growth parameters were obtained by sex and for sexes combined, from 336 illicia, between 1989 and 1993. The birthdate was assumed to be 1 January and back-calculation procedures were applied to infer the fish length at that time. Growth patterns differed by sex, and females attain a greater body length. The growth parameters were also estimated for combined sexes from the overall sample, and the sex-ratio of 1.3:1 (males vs. females) was considered to be representative of the exploited population. The growth parameters were: L∞=101.69 cm, k=0.08 year-1 and t0= - 0.2 year. The white monkfish growth parameters were estimated for sexes combined from age reading of 165 illicia from fish caught in 1990 and 1993 in Spanish waters. The southern white monkfish grows faster and attains a greater body length than the southern black monkfish. The growth parameters were: L∞=121.54 cm, k=0.102 year-1 and t0=0.032 year for the white monkfish.