Effects of rearing density on growth, brain neurotransmitters and liver fatty acid composition of juvenile white sea bream Diplodus sargus L.

摘要

White sea bream Diplodus sargus L. is a fish species that develops dominance hierarchies and aggressive behaviour against its conspecifics. On the other hand, stocking density is known to affect social interactions, while an appropriate density for D. sargus efficient farming remains to be elucidated. For this purpose, juvenile D. sargus (14.3 g) were reared in 88.4 L tanks, for 10 weeks, under six rearing densities (10, 15, 20, 25, 30 and 35 fish tank-1). Water quality was not affected by rearing density. Best growth, in terms of final weight, specific growth rate, weight variation and food utilization, was achieved at 10 fish tank-1. At this treatment the lowest body water content, hepatosomatic and splenosomatic indices, higher body and liver lipid content were also observed. Brain neurotransmitter results indicated increased dopaminergic activity in populations held at higher rearing densities, while serotonergic activity was not affected. Moreover, no significant differences were detected for liver fatty acids. Results of the present study, compared with previously reported data, suggest that, within the range tested, the lowest realistic rearing density for juvenile white sea bream would be 10 fish tank-1. Higher rearing densities led to decreased growth, which seemed to be related to changes in intraspecific competition and social behaviour..