Effects of live-release tournament regulation changes for an Iowa Largemouth Bass population

Abstract

As live release black bass (Micropterus spp.) tournaments increase in popularity, stress associated with live-well confinement may result in increased mortality rates. Variation in number of bass in tournament angler live-wells is common due to a suite of factors (e.g., regulations, number of anglers per boat, angler success), but the effect on delayed tournament mortality relative to other environmental factors is unknown. Largemouth Bass Micropterus salmoides were collected and tagged following tournament weigh-ins (n = 80) and monthly electrofishing events (n = 15) in 2018 and 2019 at Brushy Creek Lake, Iowa, USA. A Cormack-Jolly-Seber model in Program MARK was used to evaluate the duration of reduced posttournament survival (0 -7 day) and the effects of number of bass per live-well (1-15 individuals) compared to environmental covariates (air and water temperature) and bass total length on posttournament survival. Models indicated that bass survival was reduced for three days following tournament capture and was negatively related to water temperature, number of bass in live-well, and number of initial tournament mortalities. Largest effects of all covariates on tournament survival occurred at high water temperatures but were reduced at cooler water temperatures.Daily survival probability ranged from 0.9792 (95% CI: 0.9757, 0.9822) at 5.71ºC to 0.8927 (95% CI: 0.8720, 0.9103) at 28.79ºC on day of tournament capture. Survival also decreased from 14 0.9819 (95% CI: 0.9592, 0.9921) with one bass in the live-well to 0.9632 (95% CI: 0.4167, 0.9990) with fifteen bass in the live-well. However, the effect number of bass in a live-well has on overall tournament survival is likely minimal due to the infrequency of ten or more bass observed per live-well. Our study provides information on the effect number of bass in a livewell has on post-release tournament survival while providing management insights to improve post-tournament survival for recreational bass fisheries with high live-release tournament pressure.

Tournament and non-tournament anglers have little effect on a largemouth bass population compared to natural mortality

“…Increased air and water temperatures (Chapman and Fish 1985;Schramm et al 1987;Wilde 1998), increased handling times (Hartley and Moring 1995), increased number of fish per angler (Wilde et al 2002), and high live-well densities (Weathers and Newmann 1997) can all contribute to increased initial tournament mortality. Lower largemouth bass bag limits in Iowa (three fish/angler), as opposed to five fish/angler regulations in many other states (American Bass 2001; Mississippi Wildlife, Fisheries and Parks 2018) may account for the lower number of fish dying before or during the weigh-in process, although recent evidence suggests this may not be the case (Maahs 2020).…”

“…However, additional analyses conducted on this data set where large simulated increases (10-100%) in capture probabilities and decreases (10-100%) in survival probabilities resulted in relatively minor population level impacts on the largemouth bass abundance and size structure (Sylvia 2019). Consequentially, when largemouth bass natural mortality is high, additional regulations implemented to reduce fishing pressure are likely to be unnecessary or provide intended benefits (Maahs 2020;Sylvia et al 2021). Increased management of black bass paired with high catch and release rates has resulted in negative effects on growth and size-structure in some populations (see Hansen et al 2015;Miranda et al 2017).…”