Abstract:Growth and nitrogen budgets of young cobia (average initial body weight 10.0 g), yellow grouper (average initial body weight 5.5 g) and ovate pampano (average initial body weight 7.7 g) at different rations (from starvation to satiation) were studied, and the relationships between growth as well as nitrogenous excretion and ration were established in this paper. The results showed that as ration increased, specific growth rate (SGR) of young cobia increased with a decelerating pattern and there was no significant difference of SGR between satiation and subsatiation (9% per day) ration, but SGR of young yellow grouper and ovate pampano increased with a linear pattern. Among three fish species SGR of young yellow grouper and ovate pampano were similar but much slower than that of young cobia. As ration increased, feed conversion efficiency (FCE) of young cobia first increased, peaked at 9% per day ration and then decreased, but FCE of young yellow grouper and ovate pampano increased along and peaked at satiation ration. Among three fish species, FCE of young cobia and yellow grouper at satiation ration were similar, but much higher than that of young ovate pampano. Food nitrogen (CN), faeces nitrogen (FN), growth nitrogen (GN) and excretion nitrogen (UN) all increased with increased ration for three fish species. CN and UN were highest for young cobia and lowest for young yellow grouper. The nitrogen budgets of young cobia, yellow grouper and ovate pampano at satiation and subsatiation ration were 100 CN = 7.7(6.0)FN + 22.6(31.3)GN + 69.7(62.68)UN、100CN = 2.7(2.8) FN + 20.9(8.4)GN + 76.4(88.8) UN和100CN = 1.8(1.4)FN + 12.8(9.3) GN + 85.4(89.3) UN (the data in bracket indicated those at subsatiation ration), respectively. Both the proportions of food nitrogen lost in faeces and the variations of the proportions for three fish species were small. For young cobia at subsatiation ration (9% per day) the proportion of food nitrogen stored as growth was more than, and the proportion of food nitrogen lost in nitrogen was less than those at satiation ration, but contrary for young yellow grouper and ovate pampano. So among three fish species, nitrogenous excretion and nitrogen budget had an interspecific difference and increased food consumption was one of the major reasons for increased excretion nitrogen when diets contained approximate nitrogen content. Based on the specific growth rate, feed conversion efficiency, nitrogenous excretion and nitrogen budget, it could be concluded that the suitable feeding level was subsatiation ration (9% per day) or about 70% of satiation ration for young cobia and satiation ration for young yellow grouper and ovate pampano at this growth stage.