The effect of light intensity on growth of juvenile dusky kob Argyrosomus japonicus (Temminck & Schlegel 1843)

South African juvenile dusky kob Argyrosomus japonicus are more abundant in turbid estuaries than in clear marine-dominated estuaries. Turbidity can reduce light penetration into the water and create an environment different from that experienced by fish under culture conditions in mechanically filtered clear water. In order to optimize rearing conditions of this species, the effects of light intensity (23-315 lx) and feeding method (restricted ration vs. feeding to apparent satiation) on growth and food conversion ratio (FCR) of juvenile A. japonicus were assessed in a 56-day growth trial. Fish weight increased from 7.2 +/- 1.6 to 41.9 +/- 10.2 g fish(-1) at a growth rate of 3.25% body weight day(-1). Light intensity did not significantly affect growth or FCR. Feeding method did not significantly affect growth rate, but average FCR was significantly better in treatments fed a ration of 3.6% body weight day(-1) than in treatments fed to apparent satiation. Therefore, a light intensity range of 23-315 lx can be used to culture dusky kob juveniles. The better FCR in fish fed a restricted ration suggests that a ration of 3.6% body mass day(-1) allowed good growth of juvenile dusky kob.