Artificial rearing of the Black Sea turbot larvae ( Scophthalmus maeoticus)

Abstract

Eggs were taken both from spawners which matured under natural conditions and were brought on board by a trawl and from those kept in special tanks ashore. The incubation period at 16°C was about 4 days. The initial food consisted of wild microzooplankton and rotifers ( Brachionus plicatilis) at a density of 1 organism per ml, with dinoflagellates added to some diets. The rate of yolk sac absorption depended on temperature and was found to be highest at 19°C. Variations in food concentration (from 0.1 to 10 organisms per ml) did not result in any significant change of the percentage of feeding larvae or of their daily diet. The duration of digestion of one food batch (of the rotifer B. plicatilis) ranged from 3 to 5 h. The highest survival was observed when the larvae began to be fed some 120–140 h after hatching. Food selectivity indices calculated according to Ivlev's method showed that the Black Sea turbot larvae preferred larval bivalve mollusks among wild zooplankton, and that if these were not available they fed on gastropod larvae and copepod nauplii. For some unknown reason all the larvae died 8–10 days after hatching on reaching a length of 3.9–4.0 mm.