Chemical composition of effluent from high density culture of channel catfish

Abstract

Production rates of metabolic wastes by channel catfish (Ictalurus punctutas) were estimated by analyzing effluents from high density culture of 940 g and 60 g catfish. Results were integrated over a 24 h steady-state period in which normal feeding activities were maintained and were expressed as g day⁻¹kg⁻¹ fish and g day⁻¹ kg⁻¹ feed consumed. When expressed on a unit fish weight basis, production rates were greater for 60 g than for 940 g catfish. However, when expressed on a feed consumption basis, production rates of most catabolic products were approximately equal for both size fish. Average values (g day⁻¹ kg⁻¹ feed) were as follows: total N, 67; ammonia N, 20; nitrate-nitrite N, 20; 5-day BOD, 98; total solids, 180; total P, 15; total K, 18. Filtered solids from effluent contained 5% nitrogen, 1.6% phosphorus and .13%. potassium. Diurnal variation in production rates were noted with solid production reaching a maximum after each feeding and BOD, NH₃ and nitrate reaching a maximum only in the afternoon.