Effect and acceptance of bluegill length limits in Nebraska natural lakes

Abstract

Bluegill Lepomis macrochirus populations in 18 Nebraska Sandhill lakes were evaluated to determine if a 200-mm minimum length limit would increase population size structure. Bluegills were trap-netted in May and June 1998 and 1999, and a creel survey was conducted during winter 1998-2001 on one or two lakes where bluegills had been tagged to determine angler exploitation. Thirty-three percent of anglers on one creeled lake were trophy anglers (i.e., fishing for large [???250 mm] bluegills), whereas 67% were there to harvest fish to eat. Exploitation was always less than 10% and the total annual mortality averaged 40% across all 18 lakes. The time to reach 200 mm ranged from 4.3 to 8.3 years. The relative stock density of preferred-length fish increased an average of 2.2 units in all 18 lakes with a 10% exploitation rate. However, yield declined 39% and the number harvested declined 62%. Bluegills would need to reach 200 mm in 4.2 years to ensure no reduction in yield at 10% exploitation. Both yield and size structure were higher with a 200-mm minimum length limit (relative to having no length limit) only in populations with the lowest natural mortality and at exploitation of 30% or more. Although 100% (N = 39) of anglers surveyed said they would favor a 200-mm minimum length limit to improve bluegill size structure, anglers would have to sacrifice harvest to achieve this goal. While a 200-mm minimum length limit did minimally increase size structure at current levels of exploitation across all 18 bluegill populations, the populations with the lowest natural mortality and fastest growth provided the highest increase in size structure with the lowest reduction in yield and number harvested.