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

Abstract

Popularity of bass Micropterus spp. catch and release and tournament angling during the past decade has resulted in increased potential for these activities to induce population level effects. Understanding capture rates and mortality sources relative to total population mortality is essential to focus of management. We conducted monthly electrofishing, solicited non-tournament angler tag returns, and censused largemouth bass Micropterus salmoides tournaments at Brushy Creek Lake, IA, USA from April 2015 to June 2018. We used a multistate mark-recapture model to evaluate the effects of air temperature, water temperature, tournament bass per angler, and tournament initial mortality on non-tournament and tournament angler capture probability and natural, non-tournament angling, and initial and delayed tournament mortality. Average total annual mortality was 0.66 with natural mortality representing the largest mortality source (0.57) followed by delayed tournament mortality (0.06), non-tournament angling mortality (0.02), and initial tournament mortality (0.006). Our results reveal both non-tournament and tournament angling mortality are low compared to natural mortality in some lakes. Therefore, cumulative angling mortality likely has minimal population level effects on some bass populations.

Assessing Size‐Dependent Population‐Level Effects of Largemouth Bass Tournament Mortality

“…Successfully understanding the population-level changes that occur as a result of tournament fishing mortality requires two primary pieces of information: (1) the proportion of the population captured by tournament anglers and (2) tournament mortality rates. Tournament angling appears to not affect the overall abundance of bass larger than 381 mm in Brushy Creek Lake due to high natural mortality rates (Sylvia et al 2021a). However, here we hypothesized that the largest (and likely oldest and most experienced) bass would have a lower capture probability as a result of previous selective angling captures and learned behaviors.…”

“…Our estimates of population-level mortality were lower than prior size-based mortality estimates (9% for medium tournament bass and 29% for large bass: Meals and Miranda 1994; 30.8%: Weathers and Newman 1997), but our estimates approached those from studies conducted in northern latitudes, where total mortality (regardless of fish size) was 5.2% in Maine (Hartley and Moring 1995), 3.2% in Connecticut (Edwards et al 2004), 4.5% in Minnesota (Kwak and Henry 1995), 4.9% in South Dakota (Jackson and Willis 1991), and 10.5% in Idaho (Bennett et al 1989). Bass captured during tournaments at Brushy Creek Lake experienced little initial mortality (~1% annually), and delayed mortality accounts for the majority of the total tournament mortality (Sylvia et al 2021a). In this study, delayed mortality accounted for 6.0% of the total 6.1% population-level tournament mortality for medium bass and 6.8% of the 7.3% population-level tournament mortality for large bass, whereas initial mortality only accounted for 0.1% and 0.5% of the total population mortality for medium and large bass, respectively.…”

“…We then applied the mean 3-d survival rate calculated from all tournaments in the delayed mortality model to additional data from 11 tournaments in 2018 that were available for this analysis. All details of the delayed mortality model along with the delayed mortality estimates can be found in Sylvia and Weber (2019), and a similar approach using these estimates within a model is described in Sylvia et al (2021a).…”

“…Numerous studies have identified that increased water temperature, air temperature, and air exposure; handling practices (Cooke et al 2003a(Cooke et al , 2003b(Cooke et al , 2004; increased live-well confinement and density (Maahs et al 2021); and relaxed tournament regulations (Weathers and Newman 1997) can increase the tournament mortality rates of individuals. However, understanding how tournament mortality of individual bass can ultimately affect bass populations remains challenging (but see Kerns et al 2016;Sylvia et al 2021a). For tournaments to affect bass populations, they must (1) capture a large portion of the population and ( 2) have an adverse effect on the survival rate of captured fish.…”

“…For tournaments to affect bass populations, they must (1) capture a large portion of the population and ( 2) have an adverse effect on the survival rate of captured fish. Consequently, tournament mortality, even at high levels, may not affect a bass population if only a small proportion of the total population is captured annually at tournaments (Chapman and Fish 1985;Schramm et al 1987;Lee et al 1993;Edwards et al 2004;Sylvia et al 2021a).…”