Feeding response of marble goby (Oxyeleotris marmorata) to organic acids, amino acids, sugars and some classical taste substances

Weaning from live to formulated feeds is a major challenge in the culture of marble goby Oxyeleotris marmorata. It can be solved through dietary supplementation of suitable taste substance as feeding stimulant. However, there is still no information on the suitable feeding stimulant for this species. The present study was conducted to evaluate the feeding response of juvenile O. marmorata to 13 organic acids, 19 amino acids, 5 sugars and 2 classical taste substances in a concentration of 0.1 M. The response was judged through behavioural observations to determine the potential feeding stimulant. Fifty O. marmorata were conditioned to accept agar gel pellet, and then tested with the agar gel pellets that contained each of the taste substances. Pure agar gel pellet was used as the negative control. All agar gel pellets with organic acids were fully ingested by the fish (100%). Among the 19 amino acids tested, aspartic acid attained the highest ingestion ratio (94%) which was significantly different (P < 0.05) from the others. All sugars and classical taste substances were totally rejected (0%) by the fish. The taste preference of O. marmorata for organic acids seemed to be influenced by the feed pH. Strong negative linear correlation (r = −0.828; P < 0.01) was detected between the ingestion ratio and pH of the agar gel pellets when the organic acids were tested at 0.01 M. The ingestion ratio increased when the pH decreased, suggesting that the O. marmorata prefers acidic food. Evidently, all the organic acids and aspartic acid tested were potential feeding stimulants for O. marmorata. In developing weaning diets by using these taste substances, the dietary pH should be monitored as it may be one of the factors that influences the fish taste preference.