Effect of Krill Meal Supplementation in Soft-dry Pellets on Spawning and Quality of Egg of Yellowtail

Abstract

This study was conducted to clarify whether krill meal contained in the soft-dry pellets (SDP) was responsible for the improved spawning performance and egg quality of yellowtail broodstock. After the termination of a previous study, broodstock from the experimental lots fed on raw fish, moist pellets and soft-dry pellets were separately kept on a commercial SDP for about 5 months. Thereafter, the fish which had been fed entirely on SDP were offered a test diet without krill meal supplementation, whereas broodstock which had been fed moist pellets or raw fish were fed test diets containing 20 and 30% krill meal, respectively; all for about 5 months prior to spawning. The total egg production, the hatching rate among the fertilized eggs and the rate of normal larvae were the highest in the eggs obtained from the brood fish fed SDP without krill meal supplementation; these figures decreased relatively with the increase of krill meal in the diets. The rates of buoyant and fertilized eggs among the total eggs produced were not markedly different. It appears that higher levels of krill meal in the SDP was not beneficial for yellowtail brood fish.