Life history traits of Hoplostethus mediterraneus (Pisces: Beryciformes) from the north-western Ionian Sea (Mediterranean Sea)

The fish Hoplostethus mediterraneus is a bycatch of the deep-water trawling in the north-western Ionian Sea. Data on its Life history traits were collected during twelve trawl surveys carried out at two month intervals, between August 1993 and July 1995. A vertical distribution according to size was observed for this species. The year's young were recruited mainly during the spring-summer period. Sex-ratio changed by size with females larger than males. Mature specimens were found mainly between May and November with a reproductive peak during late summer. Seasonal growth was detected in the otoliths; the maximum ages of 11 and 10 y were observed in females and males respectively. Von Bertalanffy growth parameters for the whole population were: L-infinity=287.08 mm, k=0.127 y, t(0)=-2.131. No significant differences were detected between the growth patterns of the sexes. Overall growth perfomance depicted through size-distribution analysis was not significantly different from that obtained by otolith reading. Estimates of natural mortality rate for the whole population ranged from 0.14 to 0.20. Population structure, growth pattern, age at first maturity and low natural mortality rate indicate a life history mainly constituted by k-strategy characters and regulated by density-dependent mechanisms.