Time and duration of spawning by smallmouth bass (Micropterus dolomieui) in the New River drainage

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Virginia Polytechnic Institute and State University


The influence of physical parameters on spawning times of smallmouth bass and subsequent growth of young-of-the year was studied via the otolith aqeinq technique. Daily rings on the saqittae of young-of-the-year smallmouth bass were first formed the day of swim-up, and continued to be formed until growth was significantly reduced in the fall. Daily age estimates of young-of-the-year smallmouth bass collected from one unregulated section of the New River, two regulated sections of the New River, and two tributary streams of the New River were used to back-calculate spawning dates. Growth rates of young-of-the-year declined as fish got older. Smallmouth bass spawned early in the spawning season did not initially grow as rapidly as those spawned later. Spawning occurred from late-April through mid-July, 1982, at mean daily water temperatures ranging from 12.5 to 23.5 C. Frequency distributions of spawning dates were nearly identical among study sites, as were hydrological events. A major flood in June separated the spawning season at all study sites into t)lo distinct periods. Discriminant functions were developed from four water temperature variables that differentiated between daily stream conditions prior to the spawning season and daily stream conditions during the spawning season. Mean daily water temperature was the most important of the four variables in differentiating between groups of conditions.