The Fundamental Thermal Niche of Adult Landlocked Striped Bass

Abstract

AbstractResearchers have described the temperatures selected by landlocked striped bass Morone saxatilis in different locales throughout the USA. However, seasonally low concentrations of dissolved oxygen (DO) in many systems prevented striped bass from using the cool waters (<22°C) they may have preferred. In Melton Hill Reservoir, a 92‐km‐long impoundment on the Clinch River in east Tennessee, 15 adult striped bass were tagged with temperature‐sensing radio tags and tracked for an average of 418 d in 1999–2000. Cold, hypolimnetic discharges from an upstream dam and heated discharge from a steam‐generating electric facility near the midpoint of this run‐of‐the‐river reservoir provided a broad range of temperatures in most seasons, and hypoxic habitats were uncommon even during stratification. The mean temperature occupied by striped bass varied seasonally (repeated‐measures analysis of variance, P < 0.0001) and was highest in summer (17.5°C), intermediate in spring and fall (15.4–16.9°C), and lowest in winter (13.0°C). The mean and modal temperatures occupied during the growing season (May–October 1999) were 17.5°C and 19.0°C, respectively; 30% of the observations were between 9°C and 15°C. These data indicate that the fundamental thermal niche of adult landlocked striped bass may be lower than literature estimates. These results also represent the first unbiased field estimates of the influence of season on the thermal ecology of adult striped bass. The thermal characteristics of habitats considered optimal in habitat suitability index models for adult landlocked striped bass (i.e., 18– 24°C) should be revised to include cooler waters.