Movement of Adult Male Flathead Catfish in the Upper Fox River and Wolf River Systems Determinded by Radiotelemetry
Randal R. Piette and Alan D. Niebur
Abstract.—Male flathead catfish Pylodictis olivaris from the Fox (N = 24) and Wolf (N = 20) rivers in Wisconsin were implanted with 575-d radio transmitters and tracked over a 3-year period. Mean overall range of Fox River fish was 32.1 km (5.5–77.4 km) and 57.6 km (2.3–158.5 km) for Wolf River fish. Mean range was not significantly different between rivers (P = 0.158). Summer ranges averaged 16.7, 6.8, and 12.9 km for Fox River fish and 7.6, 5.6, and 4.5 km for Wolf River fish during three summers. Winter ranges averaged 2.4 and 5.9 km for Fox River fish and 3.6 and 1.9 km for Wolf River fish during two winters. Summer ranges were significantly greater than winter ranges (P = 0.048). Fish showed strong river and site fidelity returning to the same river reach and often the same woody structure in successive years during spawning and summer period. Summer site fidelity was 89% in the Fox River and 87% in the Wolf River. Winter site fidelity was 56% in the Fox River and 86% in the Wolf River. Most fish returned to wintering areas in the upper river lakes; however, 31% of Fox River fish and 25% of Wolf River fish wintered in the rivers in deep pool habitat. Fish that wintered in the rivers returned to the same pools in successive years. Upstream movement began in late April and May when water temperatures approached 15°C and stabilized in mid-June when water temperatures reached 20°C. Downstream movement began in August and peaked in September when water temperatures declined from 20°C to 15°C. Mean depth at fish locations during mid-April to mid-September averaged 2.1 m for the Fox River and 3.6 m for the Wolf River. Large woody structure was the dominant cover type used by Fox (83%) and Wolf (69%) river fish during the same time period.