Quantifying Recruitment Compensation in Florida Largemouth Bass, with Implications for Fisheries

Fish populations that undergo heavy exploitation and those for which the act of fishing can influence individual brood success are at risk of recruitment effects due to angling. The angling of brood-guarding male black bass Micropterus spp. has been shown to decrease brood success, although there is no evidence that a loss of individual broods has population-level impacts. Therefore, some level of recruitment compensation may influence juvenile bass survival. We sought to measure recruitment compensation and the form of the stock–recruit relationship for a brood-guarding species, the Florida Largemouth Bass M. salmoides floridanus (hereafter, Florida Bass). The study was conducted in four north-central Florida lakes during 4 years (2010–2013). We quantified adult stock density by using mark–recapture electrofishing surveys. The estimated broods produced in each spawning season, the number of those broods that were successful, and the age-1 recruit density were quantified via snorkel surveys. We evaluated three models for describing the effects of stock density or successful brood density on recruitment: a proportional (linear; i.e., no compensation) model, a Ricker (dome-shaped) model, and a Beverton–Holt (asymptotic) model. Recruit density was better indicated by the number of successful broods produced than by spawning stock density. Model comparisons indicated that the density-dependent models had the most support, whereas there was no apparent support for the proportional or density-independent model. The Ricker model had the most empirical support overall (estimated parameters: a = 2.2, b = 0.009). Our results indicate that the number of successful broods would have to fall below about 5 broods/ha to generate direct declines in observed average recruitment of Florida Bass.