THE IMPACT OF WINTER STORAGE OF LIVE CARP ON DISCHARGE WATER-QUALITY

Changes in water quality were studied in two flow-through winter stora ge facilities for carp from October 1994 to April 1995 (173 days), whe re unfed marketable carp (1.7 +/- 0.3 kg) from the autumnal pond harve st were held before marketing. The quality characteristics of the infl ow and outflow water and organic and nutrient loadings were summarized . Water quality parameters appeared to be affected little in these rea ring conditions. The storage facilities had no serious environmental e ffects, particularly when using a water flow rate greater than 2.6 L t (-1) s(-1) and a storage time exceeding 30 or 100 days. Dissolved oxyg en (DO) uptake resulted in 410 g per tonne of fish biomass per day (g t(-1) day(-1)) for an average flow rate of 1.7 L t(-1) s(-1) and was r elated to the flow rate (P < 0.05) and storage time (P < 0.01) of the carp. On average, pH values fell by 0.15 units and relationships betwe en pH and temperature (P < 0.001), storage time (P < 0.01) and DO upta ke (P < 0.001) were indicated. The amount of organic matter released i nto the water was 37 and 69 g t(-1) day(-1) in the case of biochemical oxygen demand (BOD) and chemical oxygen demand (COD), respectively. C orrelations between BOD production and water temperature and storage t ime were registered (P < 0.01). Nutrient enrichment reached 18 g t(-1) day(-1) as total ammonia N, and 1 and 9 g t(-1) day(-1) as orthophosp hate and total P, respectively; all were accompanied by high variabili ty in the data.