Lysine requirement of the spotted scat Scatophagus argus (Linaeus, 1766)

The study aimed to determine the lysine requirement of young spotted scat Scatophagus argus (Linaeus, 1776) (average body weight = 10.7 g). The feeding trial was conducted for 8 weeks with 5 experimental diets which were isonitrogenous, isocaloric and isolipidic (35% CP, 18.3 MJ·kg-1, containing lysine levels as treatments containing equal dietary protein (35%) and lipid levels (5%) in 3 replicates. The lysine content was from 1.22 g to 1.94 g lysine·kg-1 dry diet (35 to 55 g·kg-1 CP) with an average content of 0.18 g lysine·kg-1 dry diet per treatment. Results showed that the growth rate, feed conversion and protein efficiency ratios were significantly highest at lysine level of 1.58 g·kg dry diet-1(45 g·kg-1 CP). Fish survival was not influenced by dietary lysine. Lysine requirement level for juvenile scat was estimated using quadratic regression of the percent weight gain (PWG) and specific growth rate (SGR) against dietary lysine level to have a mean value of 1.64 g·kg dry diet-1 (4.75 g·kg-1 CP).