Aggression of guarding male smallmouth bass (Micropterus dolomieui) towards potential brood predators near the nest

Models of potential brood predators placed near the nest were used to elicit defence behaviour in male smallmouth bass (Micropterus dolomieui) in the field. The three predator models represented a conspecific, a species found in the lake (yellow perch, Perca flavescens), and a species not present in the lake (brown bullhead, Ictalurus nebulosus). Aggressive behaviour increased with brood age and with decreasing distance between model and nest. Brood-guarding smallmouth bass exhibited a generalized response to the three predator models and did not discriminate between them by altering levels of aggression.