Overwintering of farmed common carp (Cyprinus carpio L.) in the ponds of a central European aquaculture facility -: measurement of activity by radio telemetry

In the aquaculture of farmed common carp (Cyprinus carpio L.) in Central Europe, it is believed that carp overwinter motionless and without feeding at the bottom of the ponds. However, only a few studies have investigated the behaviour of carp in winter, and data on the overwintering of carp in ponds are rare. This paper presents some new data on the activity of overwintering farmed common carp in Central European aquaculture. Altogether, 14 carp were equipped with surgically implanted radio telemetry transmitters and their activity was investigated by positional tracking in a pond (2.2 ha) during the winter seasons of 1999/2000, 2000/2001 and 2001/2002. Low weight loss, WL, and good condition factor, K, suggested that overwintering was successful (AIL max. = 3.8%, K = 1.84-2.33). The carp were found to be relatively active in winter. The mean relative distances between the estimated fish positions on two consecutive tracking sessions ranged from 27.6 to 67.9 m. These activities correlated positively with water temperature in two winter seasons (p < 0.05). The findings of the present study suggest that undisturbed overwintering carp restricted their activity to certain areas of the pond, but were clearly active throughout the winter. Moreover, evidence was found that foraging occurred at water temperatures of 3.1degreesC. These findings indicate a need for further investigations not only on overwintering but also on feeding as well as on stocking densities of carp which overwinter in ponds. Refinement of overwintering methods and a reduced loss of fish should be the aim of these investigations. (C) 2004 Elsevier B.V. All rights reserved.