Evaluation of a 12.0-inch Minimum Length Limit on Smallmouth Bass in the Maquoketa River, Iowa
- 1 October 1984
- journal article
- Published by Oxford University Press (OUP) in North American Journal of Fisheries Management
- Vol. 4 (4B) , 507-513
- https://doi.org/10.1577/1548-8659(1984)4<507:eoaiml>2.0.co;2
Abstract
A 12.0‐in minimum length limit for smallmouth bass (Micropterus dolomieui) was assessed from 1980 to 1982 on a segment of the Maquoketa River, Iowa. The regulation was adopted in 1980 to control the harvest of bass, as recommended in an earlier investigation designed to identify management needs for smallmouth bass. Size structure of the bass population increased progressively, from a Proportional Stock Density of 14% in spring 1980 to 35% by the spring of 1982. However, a statistical analysis of seasonal changes indicated the improvement was not significant when compared to populations in years of no length limit. Total annual mortality of smallmouth bass averaged 53%, a reduction of 27% from previous years. Spring population densities of bass in the study area averaged 40 bass/acre (10.3 lbs/acre). A decline in bass population density and standing stock was noted, but poor year‐class success in 1978, 1979, and 1981 was responsible; a substantial year class was not produced until 1982. No adverse impacts on growth were noted. Catch success of all sizes of bass improved dramatically despite the lower densities, averaging 0.22 bass/hour, while harvest rate was 0.03 bass/hour—slightly lower than no‐length‐limit years. Harvest of small‐mouth bass by weight averaged 7.1 lbs/acre. The exploitation rate of bass ≳ 7.9 in long was 19%, a reduction of 45% from that during previous years. Exploitation of bass 12.0 in long or longer was 44%. Additional improvements in the catches included larger bass and an age structure comprised primarily of fish of ages III and IV. An empirical predictor model was reconstructed to incorporate data from this investigation and that from another study prior to the regulation. The model indicated improved production by 82%, a tripling of the PSD, and improved production of bass Age IV+ by 388%. The 12.0‐in minimum length limit on smallmouth bass improved the fishery and was accepted by a vast majority of anglers.This publication has 0 references indexed in Scilit: