LIFE-HISTORY OF THE RED MALLET MULLUS-SURMULETUS FROM THE BOTTOM TRAWL FISHERY OFF THE ISLAND OF MAJORCA (NORTH-WEST MEDITERRANEAN)

The red mullet Mullus surmuletus is one of the main target species of the trawling fishery along the continental shelf off the Island of Maj orca. The size distribution of the catches, and the reproduction, age and growth of this species have been studied based on sampling carried out from 1990 to 1992. The length range of the catches was between 10 and 32 cm, with a main distribution between 15 and 20 cm, but this in cluded small specimens (recruits of 10 to 11 cm) from August. In the > 19 cm length-class, females clearly dominated. Monthly variations in t he gonadosomatic index (GSI) and in the percentage of mature specimens showed that males spawn from December to June, whereas the reproducti ve activity of the females centres around spring. Fifty percent of mal es and females mature at 15 and 16.8 cm, respectively, corresponding t o 1 yr of age. Otolith age-readings indicate that the population explo ited in the trawl fishery consists of six age-groups; including a very high proportion of individuals between 0 and 4 yr old. Population gro wth curves revealed that females grow comparatively slowly over a long er period of time and attain greater asymptotic sizes than males. The growth parameters for the whole population are: asymptotic length, L(i nfinity) = 31.28 cm; growth coefficient, K = 0.211 yr(-1); theoretical age when length is zero, t(o) = -2.348 yr.