Effects of salinity on standard metabolic rate of juvenile marbled spinefoot (Siganus rivulatus)

Marbled spinefoot, Siganus rivulatus, is a herbivorous euryhaline teleost widely distributed in the Eastern Mediterranean. It is an economically valuable species and a suitable candidate for warm water aquaculture. Accordingly, understanding the effects of environmental factors on fish metabolism is important to optimize culture conditions. Two experiments were performed to establish standard metabolic rate and study the effect of salinity on metabolism of marbled spinefoot. In the first experiment, a series of flow-through respirometry experiments was performed at 27 degrees C and 35gL(-1). The standard metabolic rate of marbled spinefoot juveniles was calculated as 0.57 +/- 0.02mgO(2)g(-1)h(-1) (mean +/- SE). In the second experiment, fish were maintained at salinities of 25, 30, 35 and 40gL(-1) for 2weeks. Flow-through respirometry was performed to measure respiration rates at the various salinities. Respiration rates were similar among fish in salinities of 30, 35 and 40gL(-1) but increased significantly at 25gL(-1). Results suggest that despite the euryhalinity of marbled spinefoot, farmers should maintain salinity within the optimal range of 30-40gL(-1) in order to improve productivity.