Integrated culture of silver kob <i>Argyrosomus inodorus</i> and bloodworm <i>Arenicola loveni loveni</i> in abalone farm effluent

Abstract

South African abalone Haliotis midae farms utilise large volumes of seawater (c. 500–1 500 l s^–1) and produce relatively dilute effluents that are potentially suitable for the integrated culture of other species. To test this hypothesis, a marine finfish, silver kob Argyrosomus inodorus, and a detritivorous polychaete, bloodworm Arenicola loveni loveni, were cultured in abalone farm effluent and the results compared to controls reared in unused seawater. The silver kob were fed a nutritionally complete pelleted diet whereas the bloodworm were placed in shallow tanks with a low water velocity that allowed suspended organic solids to settle for the detritivorous worms to feed on. Silver kob growth rate (0.48% body weight d^–1; SE = 0.01%), mortality (1.8 ± 0.5%), feed conversion ratio (3.0 ± 0.2) and protein efficiency ratio (1.0 ± 0.1) did not differ significantly between the effluent and control treatments. Bloodworm reared in abalone effluent grew well on the particulate organic waste matter in the effluent (0.39% body weight gain d^–1; SE = 0.07%), whereas those in the seawater control lost weight at 0.19 ± 0.04% body weight d^–1 over the experimental period. Bloodworm mortality did not  significantly between effluent (6 ± 3%) and unused seawater (11 ± 8%) treatments. The faster growth of bloodworm in the abalone farm effluent was ascribed to the higher deposition rate of enriched organic solids (182 ± 56 g m^–2 d^–1) compared with those grown in the seawater control (46 ± 13 g m^–2 d^–1). It was concluded that abalone farm effluent is potentially suitable for the culture of both bloodworm and silver kob.

Keywords: finfish, integrated aquaculture, polychaete, polyculture, seawater reuse

African Journal of Marine Science 2011, 33(2): 223–228