Factors Affecting the Vulnerability to Angling of Nesting Male Largemouth and Smallmouth Bass

Abstract

Some, but not all, jurisdictions in North America have regulations in place designed to protect nesting male largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu from angling. The underlying assumption that brood-guarding males are particularly vulnerable to angling, however, is untested. In this study, we quantified the vulnerability of brood-guarding largemouth bass and smallmouth bass to angling and determined the factors that influenced that vulnerability. For this, male largemouth bass and smallmouth bass guarding newly spawned eggs were located by snorkel survey. The aggression of these males towards a brood predator was quantified, the male's susceptibility to angling lures was assessed, and the quantity of eggs in his nest and his size were recorded. Male largemouth and smallmouth bass were quite vulnerable to angling while guarding their nests, 70% of nesting male smallmouth bass and 54% of nesting male largemouth bass being hooked during the experimental angling trials. The level of aggression shown by nesting males of both species towards the brood predator model was significantly influenced by the quantity of eggs in his nest. This relationship was true regardless of male size, although larger males of both species typically received a greater quantity of eggs during a reproductive attempt. Furthermore, vulnerability to angling correlated positively with the quantity of eggs in a male's nest. Thus, the males that had the largest broods and the greatest potential to contribute to annual recruitment were the most likely to be caught by anglers, indicating that angling for nesting bass during the brood-guarding period has the potential to negatively impact bass populations.