Reproductive strategies in macrourid fish: seasonality or not?

Macrourid fish are abundantly found on the continental slope of the Ionian Sea (eastern Central Mediterranean), but the knowledge on their biology is still rather scanty. The reproductive stragegy of Hymenocephalus italicus, Nezumia sclerorhynchus and Coelorhynchus coelorhynchus was studied through data collected during 8 seasonal trawl surveys carried out between April 19 96 and March 1998. Ripe females of H, italicus and N. sclerorhynchus were f ound all year round, with a small increase during summer and autumn in the former and without any seasonal component in the latter. Few ripe females o f C. coelorhynchus were collected over the study period, with the exception of October 1996 when an increase was recorded, indicating that autumn coul d be included in the breeding season of this grenadier. The many different sizes of eggs and postovulatory follicles found in the ovaries indicate tha t all 3 species reproduce serially as multiple batch spawners. Maximum egg sizes were 1.5 mm in H, italicus and N. sclerorhynchus and 1.6 mm in C. coe lorhynchus. The highest gonadosomatic index values were found in H. italicu s, and the lowest in C. coelorhynchus. All 3 species seem to delay reproduc tion. The size at first maturity (50 % of the population) was 27 mm pre-ana l length in H. italicus, 37 mm in N. sclerorhynchus and 61 mm in C. coelorh ynchus. A seasonal continuous spawning can be assumed for N, sclerorhynchus while the low frequency of the early maturity stages in H. italicus makes it difficult to state whether or not this macrourid spawns throughout the y ear without a seasonal component. Further study is necessary to define the reproductive cycle of C. coelorhynchus.