Beyond the weigh-in: Assessing population-level consequences of Largemouth Bass tournament mortality

Abstract

Abstract Objective Fishing mortality can be a key factor regulating fish populations. Although harvest mortality previously regulated many Largemouth Bass Micropterus nigricans populations, tournament mortality is commonly believed to have been the primary source of fishing mortality since the 1990s. While mortality of tournament-captured bass can be high, it is unknown whether tournament mortality affects populations through additive or compensatory processes. Methods We conducted a Largemouth Bass capture–recapture study using a combination of 2,023 passive tags and 132 active tags, and we censused 205 tournaments across 5 years. We then used a Cormack–Jolly–Seber model to test whether tournament pressure (number of tournaments, tournament angler effort [h/ha], and number of bass weighed in) and mortality (initial mortalities and delayed mortalities) were related to population-level monthly apparent survival. Results We observed 0–12 tournaments/month (tournament effort = 0.0–8.1 h/ha) that resulted in 0–48 initial mortalities and an estimated 0–62 delayed mortalities per month. Across years, tournaments captured 17–32% of the population annually. Monthly apparent survival of Largemouth Bass was inversely related to the number of tournaments per month and declined from 0.99 at 0 tournaments/month to 0.97 at 12 tournaments/month. Models that incorporated other potential tournament metrics, including the number of initial and estimated delayed mortalities, were not supported. Conclusions Our results suggest that while initial and delayed mortality of bass weighed in at tournaments can be high, these mortality metrics were not associated with population-level survival. Instead, we found that population-level survival declined with an increasing number of tournaments more broadly, suggesting that other tournament factors (e.g., pre-fishing, catch-and-release mortality, and culling mortality) may have compounding effects with direct tournament mortality. However, the effect of tournament mortality appears low compared with natural mortality. Therefore, regulating the number of tournaments or transitioning to catch–weigh–release events could be a management tool to improve survival in systems where managers believe that tournament mortality is problematic, but such strategies may not result in population-level changes.