Preliminary Study on the Timing of Weaning of Spotted Sand Bass, Paralabrax maculatofasciatus, Larvae with a Prepared Diet

Abstract

A preliminary feeding trial was made to determine the age (size) at which spotted sand bass, Paralabrax maculatofasciatus, larvae can be weaned with a prepared diet, using survival and growth performance as evaluation criteria. For this purpose, three different dietary treatments were tested: Control: the larvae were fed on live food, then on raw minced fish fillet; treatments 1, 2, and 3: the larvae were fed on live food, then weaned with a prepared diet from 15, 25, or 30 days after hatching, respectively. The larvae were obtained from naturally fertilized eggs. There was clearly an effect of the feeding strategy on the final growth of the spotted sand bass. Standard mean length, wet weight, and specific growth rate of larvae fed on live food were significantly (P = 0.05) higher than larvae weaned with the prepared diet. A possible cause of mortality in the weaned larvae, particularly of 15-day-old larvae, may be their small size, limiting their ability to search for food or to assimilate the prepared diet, or a possible imbalance in the essential fatty acid content of the prepared diet. It appears those larvae fed a longer period of time on live food were better adapted to the shift to the nonliving diet. From the results obtained, weaning of spotted sand bass larvae with a compound diet is possible but should not be made before the larvae are 30 days old, unless a different feeding strategy, such as co-feeding, is used.