Quantifying brood predation in Largemouth Bass (Micropterus salmoides) associated with catch-and-release angling of nesting males

Largemouth Bass (Micropterus salmoides) is a highly popular and widely exploited sport fish that provides paternal care to its offspring during the reproductive season each spring. During a catch-and-release angling event, brood predators (e.g. genera Lepomis and Ambloplites) can enter Largemouth Bass nests and consume embryos, reducing the parental male’s reproductive success. While the negative impacts of angling nesting bass have been well documented, factors affecting the rate at which embryos are consumed by nest predators have not been studied at either the individual or population scale. We conducted field observations in nine lakes in southeastern Ontario and southwestern Quebec with abundant Largemouth Bass populations and varying brood predator densities to assess what factors affect how quickly brood predation begins once the male is removed, how quickly a male returns to his nest after release, and which males abandon their nests. Brood predator densities varied among lakes, and when predation occurred (65 % of all nests), it began sooner after the male was angled in nests with higher densities of brood predators nearby. The mean return time of a male was 30.0 min after being held in a live well for 15 min. The mean consumption rate (on a per-predator basis) for all nests that experienced predation was 20.9 free swimming fry predator⁻¹ min⁻¹, and the rate was higher in nests with higher mating success. The number of free swimming fry consumed was positively correlated with brood predator densities near the nest prior to angling, and the change in brood size was predictive of whether the male abandoned its nest. Predator density, parental male quality, and mating success were not associated with differences in abandonment decisions.