The effect of crowding density on growth, food conversion ratio and survival of juvenile dusky kob Argyrosomus japonicus (Teleostei: Sciaenidae)

Abstract

Dusky kob or mulloway Argyrosomus japonicus is a potential aquaculture candidate, but data on growth of this species in South Africa are missing. To determine the effect of crowding density (kg m^–3) on growth, survival and food conversion ratio, juvenile dusky kob were reared at constant densities of 10, 30 and 50 kg m^–3. Both flow index and fish density within a treatment were kept constant at 33 kg fish (m³ water flow h^–1)^–1. There were no significant differences in water quality, food conversion ratio, growth or survival between treatments, suggesting that this species can be reared using the range of conditions tested. During the 40-day growth trial fish grew at 1.3% of body mass per day, with a length gain of 0.65 mm day^–1. Average percentage survival was above 98.5% across all treatments. Thus, the highest density tested (50 kg m^–3 at 33 kg (m³ water flow h^–1)^–1) did not have a negative effect on growth or food conversion ratio.

Keywords: density indices, intensive aquaculture

African Journal of Aquatic Science 2011, 36(2): 155–158