Temperature effect on gastric emptying time of hybrid grouper (Epinephelus spp.)

Abstract

Knowledge of fish gastric emptying time is a necessary component for understanding the fish feeding rates, energy budgets and commercial production of fishes in aquaculture. The hybrid grouper Epinephelus spp. is getting popular as a culture species in Malaysia for their faster growth rate compared to commonly cultured grouper species (giant grouper Epinephelus lanceolatus and tiger grouper Epinephelus fuscoguttatus). There are data suggests that elevated sea water temperature affects gastric emptying time (GET) of fishes. Hence, this study aims to study the GET of hybrid grouper at different temperature (22, 26, 30, 34oC) in laboratory condition with commercial diet pellet. The gastric emptying times (GETs) at different temperatures were determined X-radiographically, using barium sulfate (BaSO4) as a contrast medium food marker. The food marker and X- radiography showed that initial voidance of fecal matter began 4-6 h after feeding at all temperature. The fastest GET (13 h) was obsereved in the 30°C group, whereas the longest (17 h) GET was seen in 22oC group fed with artificial diet pellet. Not much differences in GET were recorded between the 26 and 34°C groups as 34oC groups fed lesser amount compared to 26oC groups. Nevertheless a substantial delay in GET was observed in the 22°C group. The findings of this study suggest to culture hybrid grouper between 26 to 30 oC with commercial diet pellet as this temperature ranges proliferate the faster digestion process which may contribute faster growth rate of this commerical important fish species. Overall, these findings may have important consequences for optimization of commercial production of hybrid grouper.