Contamination and growth of the shrimp, Penaeus stylirostris Stimpson, cultured in a seawater/wastewater aquaculture system

Post-larval shrimp were stocked into ponds at densities of 4.5 (pond I), 6.0 (pond IV), or 30 shrimps per m3 (ponds II and III). Ponds I and II contained 10 per cent effluent in seawater, while shrimps in ponds III and IV were fed commercial pellets. The effluent was obtained from the Harbor Branch Foundation secondary treatment plant. In ponds I, II, III and IV, survival and mean weight were 29, 27, 42 and 50 per cent, and 16.2, 3.9, 4.7 and 14.8 g respectively after 5 months. Yields per ha were 210 kg (low density, effluent), 320 kg (high density, effluent), 590 kg (high density, commercial feed), and 430 kg (low density, commercial feed). The 47-54 per cent reduction in yield in ponds using effluent as the sole nutrient source could have been related to the quantity or quality of available food, or to water quality. Temperature and dissolved oxygen were similar in all four ponds, but wastewater ponds had significantly (p less than 0.05) lower salinities. Levels of PAH and phenolic compounds in water and shrimp samples were qualitatively and quantitatively similar in all four ponds. Water and shrimp samples were also analysed for cadmium, chromium, copper, lead, and selenium. Shrimp in effluent treated ponds had higher levels of cadmium (0.18-0.27 ug per g) than those in control ponds (0.12-0.13 ug per g), and higher levels of lead and selenium were found in smaller shrimps (ponds II and III). No other differences were detected.