Effects of salinity and body mass on oxygen consumption and ammonia excretion of mudskipper Boleophthalmus pectinirostris

We evaluated the effects of salinity and body mass on the oxygen consumption rate and ammonia excretion rate of mudskipper Boleophthalmus pectinirostris under laboratory conditions. Salinity and body mass had highly significant effects on the oxygen consumption rate (R O) and ammonia excretion rate (R N) (P 0.05) and highly significant (P<0.01), respectively. R O and R N of B. pectinirostris decreased significantly as the individual body mass increased. The relationship between R O and body mass was represented by R O = aW b (R 2=0.956, P<0.01). The relationship between R N and the body mass of B. pectinirostris was represented by R N = cW d (R 2=0.966, P<0.01). The R O/R N (O:N) ratios increased significantly as the salinity increased from 12 to 27, but decreased as salinity increased from 27 to 32. The atomic O:N ratios were significantly higher at 27 than at other salinity levels. The average O:N ratio was 25.25. Lipid and carbohydrate were the primary energy sources and protein was the secondary energy source within the salinity range 12–32. R O and R N were significantly higher at 27 than at other salinity levels. Our results suggest that the optimum salinity level for B. pectinirostris is 27.