Dynamics of a Heavily Exploited Texas White Bass Population

Abstract

Dynamics of a heavily exploited population of white bass Morone chrysops were assessed in the Brazos River and Lake Whitney, Texas. Fish averaging 338 mm in total length were collected by electroshocking and tagged with Floy FD-68BC anchor tags during spawning migrations in March 1988 (N = 1,550), 1989 (N = 514), and 1990 (N = 1,069). Mean length of young-of-year white bass was 224 mm. White bass were recruited to the sport fishery in their second year of life, and age-4 and older fish were rare in the population. The fishery was sustained mostly by intermediate-sized (≥230 mm) fish. In September 1988, a minimum size limit of 254 mm and a daily bag limit of 25 fish were placed on the previously unregulated fishery. Length and bag restrictions appeared to have no effect on catch rates, but they did reduce fishing pressure while maintaining fishing quality. Rewards of US$5, $10, $20, $50, or $100 were offered for returned tags. Angling exploitation was highly seasonal; more than 92% of the first-year tag returns were reported within 112 d after tagging. Eighty-eight percent of the tag returns were reported the same year that fish were tagged and 10% were reported the following year. Estimated annual angler exploitation rates (u), calculated from angler tag returns and corrected for tag loss (24.8%), were 0.54, 0.32, and 0.32 for 1988–1990, respectively, and averaged 0.47. Estimated total (fishing plus natural) mortality (A) for all ages was 0.96 in 1988, 0.80 in 1989, and 0.74 in 1990. Mortality was probably overestimated because of a high incidence of catch and release (up to 60%) and low hooking mortality rates and may represent a worst-case scenario.