Summer Movements of Sub-Adult Brook Trout, Landlocked Atlantic Salmon, and Smallmouth Bass in the Rapid River, Maine

ABSTRACT

Summer movement patterns and spatial overlap of native sub-adult brook trout (Salvelinus fontinalis), non-native landlocked Atlantic salmon (Salmo salar), and non-native smallmouth bass (Micropterus dolomieu) in the Rapid River, Maine, were investigated with radio telemetry in 2005. Fishes were captured by angling, surgically implanted with radio transmitters, and tracked actively from June through September. Most brook trout (96%) and landlocked salmon (72%) displayed long distance movements (>1 km) to open water bodies (28 June to 4 July) followed by periods of time spent in presumed thermal refigia (5 July to 16 September). Summer water temperature rose above 25 °C, near the reported lethal limits for these coldwater species. In contrast, the majority of smallmouth bass (68%), a warrnwater species, did not make long distance movements from areas of initial capture, remaining in mainstem sections of the river (28 June to 16 September). Spatial overlap of smallmouth bass and brook trout in the summer is unlikely because brook trout presumably move to thermal rehgia during this time. However, interspecific competition between brook trout and landlocked salmon may occur since they select similar habitats June through September.