Summer Habitat Selection of Striped Bass in Lake Norman

Lake Norman is a 13,516-ha reservoir frequently devoid in late summer of the cool, well-oxygenated water preferred by mature striped bass {Morone saxatilis). Large summer striped bass kills, however, are rare. The objective of this study was to determine the summer temperature and dissolved oxygen (DO) levels in habitat used by striped bass in Lake Norman. We tagged 48 striped bass (2.2-7.8 kg) with temperaturesensing radio tags (40-50 MHz) during spring 1992 and 1993. Tag frequency, tag temperature, location, and a water column temperature/DO profile were recorded for each tag encounter. Mean tag temperatures (25.6 and 26.1 C) and associated mean DO concentrations (4.0 and 3.1 mg/liter) were similar for large (>4.5 kg) and small (<4.5 kg) striped bass in the warmest weeks of summer 1992. Habitat <28.0 C and containing >2.0 mg/liter DO was always present in most of Lake Norman both years. No striped bass mortalities attributed solely to environmental conditions were observed. We suggest DO >2.0 mg/liter and water temperature <27.0 C will prevent summer striped bass mortalities in Lake Norman. Water temperatures up to 28.0 C can be tolerated, but the exposure period must be <4 weeks to avoid mortalities.

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