Effect of water temperature on the timing of initial feeding of Persian sturgeon Acipenser persicus larvae

The initial feeding time for fish larvae is considered a critical period because it influences their subsequent survival and growth.This study was carried out to elucidate the effects of water temperature on initial feeding of Persian sturgeon Acipenser persicus larvae.The larvae were stocked in three large circular fiberglass tanks that were supplied with 16 ± 4 l /min/tank of water at 3 different temperatures (15, 16 and 17 °C).The effect of the first feeding on the growth was tested by providing feed beginning on day 9 and was continued on days 10, 11, 12, 13 and 14 post hatch.The larvae were fed on newly hatched Artemia nauplii at 50% body weight/day.Thirty fish larvae were randomly sampled from each experimental tank on day 8 every 4 hours to determine gut content and the presence of melanin plug in the hindgut.However, exogenous feeding occurred in our study on days 12, 11 and 9 post hatch at 15, 16 and 17 °C, respectively.Food in larval stomachs was observed at the same time that melanin plug was present in the hindgut. Therefore the expulsion of melanin plug can not really be used to determine the time of transition to active feeding. These results confirmed that temperature affected timing of digestive tract development of fish larvae and food should be offered to sturgeon larvae when the gut gets ready for food absorption anatomically and physiologically.