Feeding habits and growth characteristics of larvae and juvenile hybrid grouper (Epinephelus fuscoguttatus♀×E. polyphekadion♂)

Hybridization is the most effective and thus widely used technique in the artificial breeding of grouper. Feeding habit is one of the most crucial variables for feeding strategy in early development stage of fish. Diet and feeding time with good feeding habit will increase the survival rate and the feed efficiency greatly. In order to understand the feeding characteristics of hybrid grouper(Epinephelus fuscoguttatus♀×E. polyphekadion♂) during the early development stage, feeding habits and growth of larvae and juveniles in condition of artificial culture were examined by using ecological method of simple random sampling at water temperature of 27.5–31 °C. Results showed that hybrid grouper had already acquired good foraging capability at larvae stage. 3 days after hatch (DAH) opened its mouth and started to feed and feeding incidence was 40%. At 3 DAH, feeding incidence was 100% of larvae and juvenile. Feed intake of larvae and juvenile increased with the increase of body mass, which can be expressed by binomial equation. The fullness coefficient of stomach fluctuated in the range of 0.95%−11.26%. Larvae and juveniles could spend less than 1.5 h on feeding from empty to full in stomach, the larvae spend 0.5−1 h on digesting rotifers and 1−2 h on digesting copepods larvae, and the juveniles spend 1.5−3.5 h on digesting copepods adult. The daily feeding intake rates of hybrid grouper were 49.85%(5 DAH),22.55%(10 DAH) and 15.72%(24 DAH), which could be a reference for daily feeding of larvae and juvenile in artificial seedling. The feeding behavior of hybrid grouper larvae and juveniles mainly occurred at daytime. They had obvious circadian rhythm of feeding.The feeding rhythm of larvae (3 DAH and 10 DAH) exhibited feeding peak at 9:00 and 18:00, and the feeding peak of 24 DAH larvae was at 12:00. The average daily growth rate was 7.96% and the average daily weight gain was 28.73% during the 3−30 DAH larvae and juveniles. The relationship between total length, body weight and age (in days) can be expressed as exponential equation, respectively. The relationship between body weight (y) and total length (x) could be expressed to be y=0.037 3x^{2.537 8}, b=2.537 8 is approximately equal to 3. It shows that the growth of lavae and juveniles of hybrid grouper belongs to the type of isokinetic growth.