Effects of Temperature and Streamflow on Time and Duration of Spawning by Smallmouth Bass

The influences of eight water temperature and three discharge variables on the time and duration of spawning by smallmouth bass Micropterus dolomieui were evaluated in three mainstem sections and two tributaries of the New River in Virginia and West Virginia. Stepwise discriminant analysis was used to assess the relative importance of each variable in distinguishing between days when spawning did and did not occur. Spawning occurred from late April through mid-July 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 was the timing of hydrologic events. Spawning activities were interrupted by flooding in June and resumed when water levels were receding. Mean daily water temperature explained most of the variation among groups of daily stream conditions related to spawning activities. Discriminant functions developed from three temperature variables and one discharge variable correctly classified 72% of the days on which spawning did and did not occur. The functions should be useful in predicting smallmouth bass spawning times in other streams.