Seasonal and day-night fluctuations in the trawl catches of the edible crab Penaeus kerathurus at the locality »ušće Bojane«

Abstract

        Penaeus kerathurus inhabits muddy and muddy-sandy bottoms. Such a region is the mouth of the Bojana where this species was found in large quantities.

       In order to analyze and compare the catches more easily we have decided upon a relative number, registered as index 100, whose value is equal to the average number in the catches of Penaeus kerathurus by the first exit of the trawler at the standard station 32a. This relative number is the index of the occurrence of this crab in the trawls for a certain period of the year. During these investigations we have come to the conclusion that the catches during the day hours (6-12 a.m. and 12-6 p.m.) are incomparably greater than during the night hours. We have also noticed that the time of the occurrence of this crab moves from the night moon (October) to the early morning one (November and December).

        By night this species is replaced by Solenocera membranacea in limited quantities.