Effects of stocking density on behavior and growth performance of Epinephelus fuscoguttatus ♀× Epinephelus lanceolatus ♂

ObjectiveEffects of stocking density on ingestion behavior, growth, blood physiological and biochemical indexes of Epinephelus fuscoguttatus♀×E. lanceolatus♂were evaluated to provide reference for its breeding under indus-trial conditions. MethodUnder industrial conditions, three stocking densities 60, 100 and 140 ind/m3 were set, and the breeding cycle was 50 d. Ingestion behavior of E. fuscoguttatus♀×E. lanceolatus♂ was recorded, and its growth perfor-mance and blood physiological and biochemical indexes were measured. ResultIn terms of ingestion behavior, as breeding cycle extended and stocking density increased, the ingestion patterns of juvenile E. fuscoguttatus♀×E. lanceolatus♂showed a certain regularity, and basically followed cone-calathiform-agglomeration-tiling type. With increase of stocking density, the proportion of E. fuscoguttatus♀×E. lanceolatus♂in upper layer of ingestion gradually reduced and the cor-responding average ingestion rates were 80.0%(60 ind/m3), 72.0%(100 ind/m3) and 66.7%(140 ind/m3). In addition, the proportion of ingestion level 1 also gradually reduced and the average proportions were 82.7%(60 ind/m3), 73.3%(100 ind/m3) and 64.0%(140 ind/m3). In growth performance, average weight gain, daily weight gain, feed conversion rate and growth efficiency declined with the increase of stocking density; feed coefficient increased as stocking density increased, the dif-ferences between groups were significant(P<0.05, the same below). But effects of stocking density on body length, whole length, weight gain rate, growth rate, specific growth rate and survival rate did not reach significant level(P>0.05, the same below). In terms of blood biochemical indicators, with the increase of stocking density, white blood cell content of E. fuscoguttatus♀×E. lanceolatus♂ rose, but glucose content remained stable. There was no significant difference between groups. Taking all the indxes into consideration, 100 ind/m3 was the optimal stocking density. ConclusionExcessively low density or high stocking density are not beneficial for growth of E. fuscoguttatus♀×E. lanceolatus♂, the optimum breeding density was 100 ind/m3 for its breeding under industrial conditions. This stocking density can ensure the healthy growth of E. fuscoguttatus♀×E. lanceolatus♂, reduce production costs, and obtain desired economic benefits.