Home Range of Esox lucius in Lake Itasca

Abstract

Northern pike, Esox lucius, are freshwater predatory North American fish renowned and beloved by anglers for their fierce fight and delicious filets. Pike are ambush hunters; light vertical stripes on a dark green background blend into vegetation in shallow, sunlit waters. Pike are most active at dawn and dusk, likely because their prey is as well. Pike survive best in cold, well-oxygenated mesotrophic lakes and often times won’t breed and even starve themselves if conditions are too warm. The objective of this study was to monitor the movements and activity levels of pike in Lake Itasca in north central Minnesota. Pike were chosen because their large body size and lack of predators negate the majority of the concerns that the encumberment and extra weight of a radio transmitter, whether it be internal or external. Internal transmitters with external whip antennas were used in preference of external transmitters and internal transmitters with encapsulated helicoil antennas because they would encumber the fish less. Whip antennas also provide more range, transmitting a strong signal into the water from any angle. A helicoil antenna projects its signal down the central axis of the coil, meaning the antenna would have to be pointed directly into the antenna coil, which could slow tracking by limiting the angles a fish can be located from. However, externally projecting antennas have been shown to collect algae and contribute to fish mortality at high temperatures (Ross & McCormick, 1981). To combat this, the water temperature in Lake Itasca averages 20°C during the summer months, sufficiently slowing algal growth along the antenna.