Quality of waters discharged from fishponds during the fall carp (Cyprinus carpio L.) harvest

Abstract

The work presented contributes to the quality assessment of fishpond waters discharged into a river during the fall carp, Cyprinus carpio L., harvest, of waters discharged before and after fishing, and of riverine waters that feed the ponds. The subject of the study was a complex of ponds with semi-intensive carp production situated in the upper catchment of the Vistula River (southern Poland). While the water reaction or pH, the concentration of dissolved oxygen, and the biochemical (BOD5) and chemical oxygen demand (CODMn) in the pond effluents exceeded the respective concentrations in the river waters, they did not exceed permissible levels of contamination for surface river waters. The only exception was the concentration of total suspended matter, which also exceeded these limits in river waters. The value of BOD5, CODMn, CODCr, and suspended matter in the pond water increased towards the end of the fish harvest when the bottom water layers, equal to about 10% of the entire pond volume, were discharged. During the fish harvest the average diurnal pond loads exceeded more than once the loads before and after the harvest and more than twice the loads in riverine waters. The pond loads decreased decidedly after cold, cloudy weather in July and August. The share of the net pond load (pond load minus river load) in that of the river ranged from several to a few dozen percent. In very warm, dry seasons the share of the pond load increased exceptionally to over 100% due to low water flow in rivers. However, in very wet, cold seasons the share of this decreased to just a few percent due to high water levels. An exception to this was the extreme cold of November 1998 when the share of pond BOD5 increased considerably. After the fish harvest the concentration and loads of the investigated parameters of pond and riverine waters declined distinctly and were approximate to each other; an additional decrease was observed after cold weather in October.

CORRESPONDING AUTHOR:

Prof. dr hab. Maria Anna Szumiec, Polska Akademia Nauk, Zakład Ichtiobiologii i Gospodarki Rybackiej w Gołyszu, 43-520 Chybie: Tel./Fax: +48 (33) 8563778, +48 (33) 8589292;
e-mail: zigr@fish.com.pl, maszumiec@wp.pl