MEPS 184:189-196 (1999)  -  doi:10.3354/meps184189

Reproductive strategies in macrourid fish: seasonality or not?

G. D'Onghia*, M. Basanisi, A. Matarrese, F. Megli

Department of Zoology, University of Bari, Via Orabona 4, I-70125 Bari, Italy

ABSTRACT: 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 1996 and March 1998. Ripe females of H. italicus and N. sclerorhynchus were found 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 of C. coelorhynchus were collected over the study period, with the exception of October 1996 when an increase was recorded, indicating that autumn could be included in the breeding season of this grenadier. The many different sizes of eggs and postovulatory follicles found in the ovaries indicate that 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. coelorhynchus. The highest gonadosomatic index values were found in H. italicus, and the lowest in C. coelorhynchus. All 3 species seem to delay reproduction. The size at first maturity (50% of the population) was 27 mm pre-anal length in H. italicus, 37 mm in N. sclerorhynchus and 61 mm in C. coelorhynchus. Aseasonal 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 year without a seasonal component. Further study is necessary to define the reproductive cycle of C. coelorhynchus.

KEY WORDS: Biology · Reproduction · Macrourids · Mediterranean

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