مقايسه عادات غذايي تاسماهي ايراني (Acipenser persicus) و ازون برون (Acipenser stellatus) در سواحل جنوبي درياي خزر

Summer and winter feeding behavior in Acipenserpersicus and Acipenser stellatus in the south Caspian Sea

Feeding behavior in Acipenser persicus and Acipenser stellatus in summer and winter was studied from 2004 to 2006 simultaneously with the marine survey for sturgeon stock assessment. Bottom trawls (9m) on board the research vessel Sisara 2 (50 hsp) were used to collect specimens at depth below 10m, while specimens at depths more than 10m were collected using bottom trawls (24.7m) on board the Guilan Research Vessel (1000 hsp). Examination of stomach contents of 135 A. persicus and 80 A. stellatus specimens revealed that the food spectrum was composed of bony fishes (Neogobius sp.y Atherina sp., Clupeonella cultriventris), invertebrates belonging to the family Ampharitidae (polychaeta worms including Hypanai sp. and Nereis diversicolor), various crustaceans (Gammarus sp. and Paramysis sp.) and the bivalved mollusc, (Abra ovata). Significant differences were detected in the frequency of prey items in the different seasons studied. Also significant differences (P<0.05) were also detected between prey frequency and length at 95% confidence level with the greatest differences recorded in the <50cm and in the 50-100cm length classes. It is evident from the results obtained that specimens belonging to the 50- 100cm length class showed the highest diversity in food items in all the seasons studied. Highest frequency of food items was consumed by A. stellatus in the <50cm and in the 50- 100cm length class, which were not significantly different (P<0.05) in the two seasons studied. In the present study no significant differences were recorded in the main food items consumed by A. persicus and A. stellatus in the <100cm length class and both species fed on (Ampharitidae) worms at depths less than 10m (P>0.05).