Effects of Length and Bag Limits on Largemouth Bass Tournament Capture and Mortality

Abstract

Tournament mortality of Largemouth Bass Micropterus salmoides can be a major source of population mortality. Tournament captures and mortality may be reduced through restrictive harvest regulations (bag and length limits), but these approaches for mitigating tournament mortality have not been assessed. We assessed the effects of bass tournament angler bag and minimum length limits on the number of bass weighed in, bass tournament weigh-in probability, and the reduction in tournament mortality. We tagged nearly 4,000 Largemouth Bass during 205 tournaments and electrofishing events at Brushy Creek Lake, Iowa, from 2015 to 2019. We then used a before–after–control–impact analysis to evaluate the effect of tournament regulations (bag limit: either three or five bass; minimum length limit: no minimum or 305, 330, 356, or 381 mm) on bass monthly catch rates and a capture–recapture model to assess tournament weigh-in probability among regulation types. Number of bass per tournament angler-hour was similar among a three-bass, ≥381-mm length limit and more liberalized regulations (mean = 0.26 bass/angler/h). Length and bag limits had little effect on bass weigh-in probability. We estimated that reducing the bag limit from five to three bass would have little effect, while a reduction from three to two bass would reduce the number of bass weighed in by 35% and a bag limit of one bass would result in a 62% reduction. Alternatively, a minimum length limit of ≥381 mm could reduce the number of bass weighed in by over 40%. Tournament mortality was greatest in July and August, but low catch rates during these months resulted in little mortality. Although current length and bag limits did not affect bass weigh-in probability, the number of bass weighed in and associated tournament mortality may be reduced if bag and length limits are very restrictive (≤2 bass/angler or minimum length ≥381 mm). However, restrictive tournament regulations may not be biologically necessary or socially acceptable.