Response of Smallmouth Bass to Regulatory and Environmental Changes in Elkhorn Creek, Kentucky

Abstract

Populations of smallmouth bass Micropterus dolomieu in Elkhorn Creek, Kentucky, were managed by means of a 12.0-in minimum length limit from 1978 through 1992. During this period, these populations were characterized as having a poor population size structure dominated by high densities of slow-growing, sublegal fish. In 1993, the length limits were changed on a 16.0-mi section of the main-stem Elkhorn Creek to a 12.0–16.0-in protective slot limit, and the statewide, six-fish creel limit was modified to allow in the creel only two fish greater than 16.0 in. Length and creel limits remained unchanged on the rest of the stream. Both sections of stream were sampled during pre-slot-limit (1990–1993) and slot limit years (1994–2000) to determine whether the protective slot limit improved the quality of sport fishing. Declines in stock densities (catch per unit effort) of 8.0–11.9-in smallmouth bass, initial large increases in the densities of fish within the protective length limit, and increases in the densities of 16.0-in and larger smallmouth bass in the main-stem Elkhorn Creek were noted. The growth rates of smallmouth bass remained unchanged, however, following the length limit change. Smallmouth bass year-class production and growth to age 1 were both highly variable and inversely related to April−July rainfall. In addition, the recruitment of smallmouth bass to the fishery as age-4 and older fish was positively correlated to the densities of spring-collected, age-1 smallmouth bass. Variable recruitment patterns resulted in fluctuations in the densities of fish below, within, and (in the future) possibly above the experimental slot length limit. Overall, the slot limit regulation on smallmouth bass in the main-stem Elkhorn Creek provided for increased sport fishing quality, particularly when strong year-classes recruited to the protective slot limit.