RESTRICTED SUMMER HABITAT AND GROWTH OF NORTHERN PIKE IN 2 SOUTHERN OHIO IMPOUNDMENTS

Available summer habitat for northern pike Esox lucius in southern Ohi o impoundments is restricted by warm epilimnetic temperatures and anox ic bottom waters. We used temperature-sensitive radio transmitters to determine locations of adult northern pike in two impoundments, and we related seasonal growth of other tagged fish to availability of suita ble habitat. We implanted transmitters in eight fish in one lake and n ine fish in the other; fish locations were monitored from April to Oct ober. Condition factors were highest in spring and lowest in late summ er. Individually tagged fish lost weight during summer. At the onset o f summer thermal stratification, fish moved from inshore to offshore l ocations that were frequently associated with macrophytes or bottom st ructures such as submerged stream channels. When lake surface temperat ures exceeded 25-degrees-C, fish were found in the coolest available w ater with dissolved oxygen concentrations of at least 3.0 mg/L, and th ey were restricted to this stratum for 2-3 months. Although northern p ike lost weight during the period of habitat constriction, their annua l growth exceeded the average for the species.