Population Structure, Sex Ratio, Cpue And Reproductive Aspects Of Melicertus Kerathurus And Penaeus Aztecus In The Thermaikos Gulf, Aegean Sea

The east Atlantic-Mediterranean Melicertus kerathurus and the west Atlantic invader Penaeus aztecus co-exist in the Thermaikos Gulf (Aegean Sea) and the two penaeid prawns are exploited by both artisanal and trawl fisheries. The bulk of catches for otter trawling consisted of M. kerathurus. Alpha rtisanal fishery catches for both species presented significant monthly fluctuations: Catch Per Unit Effort (CPUE) of M. kerathurus being higher in summer, whereas for P. aztecus in early autumn. For both species size frequency distributions and medians differed significantly between sexes, in favor of females. Females and males P. aztecus have a significant higher median size than the respective of M kerathurus. Sex ratio of M. kerathurus from the artisanal fishery showed a significant monthly differentiation, with males dominating in June and July whereas females from August to October. Females P. aztecus outnumbered males in catches for both trawl and artisanal fisheries. The two species have prolonged reproductive periods which overlap, but with distinctive spawning peaks: M. kerathurus in mid-July and P. aztecus in September-October. It is documented that P. aztecus is well established in the Thermaikos Gulf and has not led to any up-to-date bathymetric displacement or to the extinction of M. kerathurus.