Effect of salinity on growth of juvenile silver kob, <i>Argyrosomus inodorus</i> (Teleostei: Sciaenidae)

Abstract

As part of the evaluation of new aquaculture species, the effect of environmental factors on growth, food conversion ratio and survival should be tested. In this study silver kob, Argyrosomus inodorus, were reared for 98 days at three salinities, of 15, 25, and 35, at an average water temperature of 18 °C. Fish were fed to satiation twice daily. There were no differences between treatments in mass gain, feed conversion ratio, feeding intensity (% body mass d^–1), blood osmolality, or survival. During the first 84 days there was also no difference in length gain (mm d^–1) between treatments although the last 14 days of the study suggested a small but significantly higher average length in fish from the 25-salinity treatment. Silver kob grew at a rate of 0.31 to 0.37 mm d^–1 and food conversion ratio averaged 2.33 kg food per kg gain at a feeding intensity of 1.6% body mass d^–1. Blood osmolality did not differ between fish reared at different salinities. We conclude that silver kob perform at least as well at reduced salinities as in full strength seawater. This could lead to significant cost savings when rearing fish inland using artificial seawater.

Keywords: fish physiology; mariculture; mulloway; osmolality; salinity tolerance

African Journal of Aquatic Science 2008, 33(2): 161–165