EFFECT OF THE FORMULATED DIETS ON PERFORMANCE AND RESISTANCE OF JUVENILE ABALONE (Haliotis discus, Reeve) SUBJECTED TO THE VARIOUS STRESS CONDITIONS

Performance and stress resistance of juvenile abalone (Haliotis discus) fed the formulated diets substituting fish meal (FM) and macroalgae (MA) with soybean meal (SM) and rice bran (RB), respectively, was compared with the MA for abalone culture against various stress conditions. Eighty four thousand juvenile abalone averaging 4.3 g were distributed into twelve 5 ton tanks (7,000 abalone per tank). Four experimental diets (Standard, FM50, FM50+MA50 and FM50+MA100 diets) were prepared in duplicate and extruded by a commercial pelleter. The 50% FM, the combined 50% FM and 50% MA, and 50% FM and 100% MA were substituted with the same amount of SM, the combined SM and RB, respectively in the FM50, FM50+MA50 and FM50+MA100 diets. The dry MA (Undaria pinnatifida and Laminaria japonica) were prepared to compare effect of the experimental diets on performance of abalone. At the end of the 16-week feeding trial, sixty randomly chosen abalone were distributed into 3 of 70 L plastic rectangular containers. Twelve of 70 L plastic rectangular containers from each tank were randomly placed into 1 ton indoor plastic tank and 3 of 1 ton tanks were used for stress resistance of abalone subjected to the various stress conditions (air exposure, sudden salinity and temperature changes).

Survival, weight gain and specific growth rate of abalone fed the all formulated (Standard, FM50, FM50+MA50 and FM50+MA100) diets were significantly higher than that of abalone fed the MA. The cumulative mortality of abalone fed the MA and Standard and FM50 diets was significantly higher than that of abalone fed the FM50+MA100 diet, in 100 h after air exposure. The cumulative mortality of abalone fed the MA (U. pinnatifida and L. japonica) was significantly higher than that of abalone fed the all formulated diets at 72 h after sudden salinity change (Fig. 1). The cumulative mortality of abalone fed the MA was significantly higher than that of abalone fed the all other diets since 96 h after sudden salinity change. The lowest cumulative mortality was obtained in abalone fed the FM50+MA50 diet, followed by the FM50, FM50+MA100, FM50 and Standard diets, then L. japonica and U. pinnatifida at 80 h after sudden temperature change. In conclusion, the well formulated diets produced better growth performance of abalone over the dry MA. Abalone subjected to the various stress conditions after being fed with the all formulated diets, was more resistant than those fed the MA.