Recruitment and post-settlement growth of juvenile Merluccius merluccius on the western Mediterranean shelf

Abstract

Young-of-the-year European hake (Merluccius merluccius) were sampled during four seasonal cruises between November 1998 and September 1999. The greatest numbers and biomass were found in spring 1999. Some 73% of juvenile fish in terms of number, and 81% in terms of biomass, were caught at depths between 60 and 160 m on the outer western Mediterranean shelf, where the water temperature ranged between 13.5 and 14°C. The length composition of samples showed there to be small hake all year around, with modes between 7 and 11 cm total length depending on the season. Otolith analysis was used to establish age at settlement (62.7 days) and to determine seasonal growth. The monthly growth rates ranged from 1.2 cm month-1 for juvenile hake captured on February 1999 to 2.5 cm month-1 for ones captured in June. The growth rates are related to survival, as was shown by the calculated hatch dates and relative abundances of recruits. This work provides information on the first year of life, recruitment and growth processes in an important species of the Mediterranean demersal ecosystem which is heavily exploited by a recruitment fishery.

Juveniles de la merluza europea fueron muestreados durante cuatro cruceros estacionales realizados entre 1998 y 1999, la mayor biomasa se encontró en la primera de 1999 y entre 60 y 160 m. de profundidad. Las tasas de crecimiento están relacionadas con la supervivencia. Este trabajo provee por primera vez información sobre el primer año de vida.