Winter residency and activity patterns of channel catfish, Ictalurus punctatus (Rafinesque), and common carp, Cyprinus carpio L., in a thermal discharge canal

Radiotelemetry was used to examine the behavioural responses of fish to dynamic environmental and operating conditions in a fossil-generating power station discharge canal on Lake Erie. A series of seven underwater antennas continuously monitored the movements of 10 common carp, Cyprinus carpio L., and 10 channel catfish, Ictalurus punctatus (Rafinesque), in the 550-m discharge canal between 23 December 1997 and 1 May 1998. Common carp residency values were higher (47.71±8.51%) than those of channel catfish (10.15±2.82%). While resident in the discharge canal, channel catfish spent more time in the upper reaches and were more active than carp. Carp spent more time in the lower reaches of the channel, and made more frequent movements between the canal and Lake Erie. Overall residency decreased significantly during the study period. Aside from significant negative correlations between common carp residency and daily mean influent temperature ( r = ?0.53), daily discharge mean ( r = ?0.30) and minimum water temperature ( r = ?0.47), and positive correlations to daily mean cooling water flow ( r = 0.38), the activity and residency of tagged individuals were independent of environmental and operating conditions. There was no relationship between the total length of each fish, and any of the residency or activity indices. The implications of extended fish residency in heated discharges and the utility of radiotelemetry as a monitoring procedure are discussed.