Effects of a Conservative Rock Bass Length Limit on Angler Participation, Sport Fish Populations, and Crayfish Prey in a Missouri Ozark Stream

Abstract

AbstractRock bass Ambloplites rupestris are popular with anglers in Missouri Ozark streams, second only to smallmouth bass Micropterus dolomieu. Historically, fishery biologists emphasized the management of smallmouth bass, but in the late 1980s they sought higher‐quality rock bass fisheries and thus the information needed to recommend harvest regulations. Using a conservative minimum length limit of 230 mm (9 in) total length (TL) in a heavily exploited rock bass fishery in the Big Piney River, Missouri, we assessed the direct and indirect effects on angler participation and attitudes (by means of an angler survey), the abundance (mark–recapture analysis) and growth rates (scale analysis) of rock bass and smallmouth bass, sport fish predation on crayfishes (order Decapoda; diet analysis), and crayfish densities (stratified quadrat sampling). These measures were evaluated for 3 years (1992–1994) before the length limit was imposed and for 6 years afterward (1995–2000) on a 17.1‐km‐long regulation section and a 10.4‐km‐long reference section. Our results indicate that the length limit (1) had substantial angler support, as shown by their attitudes and compliance with the regulation; (2) reduced the hours fished by rock bass anglers, smallmouth bass anglers, and all anglers; (3) increased the abundances of larger rock bass and smallmouth bass substantially; (4) did not reduce the growth rates of rock bass or smallmouth bass; (5) did not proportionally reduce the predation on crayfishes or increase the percentage of empty stomachs; and (6) did not reduce the densities of crayfishes. After a review of the options for long‐term management, fishery administrators and managers elected to manage Big Piney River rock bass with a minimum‐TL regulation of 205 mm (8 in) on 124 km of river. Managers on five other rivers (one with shadow bass A. ariommus) have done likewise on an additional 448 km, and the outcomes of these decisions are currently being monitored on all six rivers.