Population structure, age and growth of macrourid fish from the upper slope of the Eastern-Central Mediterranean

Hymenocephalus italicus, Nezumia sclerorhynchus and Coelorhynchus coelorhyn chus were found in 80, 75 and 69% of trawl hauls carried out between 250 an d 750 m on the upper slope of the Ionian Sea. The abundance of H. italicus and N. sclerorhynchus increased with depth while in C. coelorhynchus the hi ghest densities were observed in the uppermost 500 m. In all three grenadie rs the average size increased with depth. The populations had a multimodal size-frequency distribution. In H. italicus adults were generally more repr esented in the population and the abundance of juveniles varied with season s. In N. sclerorhynchus and mostly in C. coelorhynchus the bulk of the popu lation was generally made up of small individuals the year round. In N. scl erorhynchus a seasonal pattern was shown in the depth distribution of juven iles. The sex ratio was in favour of females in larger specimens and in eac h bathymetric stratum. Seasonal growth was detected in the otoliths of the three species. Maximum ages were around 9 years in H. italicus and N. scler orhynchus; 8 years in C. coelorhynchus. Although some differences have been detected in the population ecology of the three species, they are characte rized by a prolonged recruitment during the year, slow growth, longevity an d delayed maturity. (C) 2000 The Fisheries Society of the British Isles.