Urban and Community Fisheries Programs: Development, Management, and Evaluation

Growth, Mortality, and Harvest of Walleye and Hybrid Striped Bass in an Iowa Urban Lake: Simulated Effects of Minimum Size Limits

Randall D. Schultz and Benjamin J. Dodd

doi: https://doi.org/10.47886/9781934874042.ch37

Abstract.—Growth, exploitation, and natural mortality of walleyes Sander vitreus and hybrid striped bass Morone chrysops x M. saxatilis were investigated in Lake Manawa during 2005 and 2006. The major objectives were to assess the contribution of these popular sportfish species in an urban situation and to determine the potential benefits of regulation reductions. Lake Manawa is a 320 ha natural lake in Council Bluffs, Iowa. Currently, walleyes are regulated only with a creel limit of 5 and possession limit of 10, and hybrid striped bass are not regulated. Growth of walleyes (through age 8) was average to slightly above average that of other North American populations, while growth of hybrid striped bass (through age 5) was average to slightly lower. Significantly more walleyes and hybrid striped bass were caught than harvested; exploitation rates were estimated at 24% for both species. Instantaneous total mortality rates (Z) for walleyes and hybrid striped bass were less than 40%, and corresponding survival rates (S) approached 70%. Regulation models predicted that length limits on either species would have negligible effect on yield, but decrease harvest greatly. We conclude that natural mortality plays a greater role in the abundance and fishing quality of walleyes and hybrid striped bass in this urban lake than do angler effects, and regulation changes are not warranted, especially considering that usage rates indicate that education and communication efforts are not adequately promoting these fisheries.