We’ve mentioned male parental care in fish before, (Daddy Daycare) but we recently witnessed this smallmouth bass (Micropterus dolomieui) guarding its nest while diving in a Central Sierra reservoir. As temperatures warm-up (55-60°F/13-16°C) in the spring, or in this case summer, male smallmouth bass will use their fins to clear off sand or gravel in shallow (.5-5m) areas near cover (Moyle 2002). Once a male establishes a nest he will defend it from other males. Ripe females will approach with a characteristic head down position to entice the male to spawn with them. When the male is convinced to spawn, the female will lay 2,000-21,000 eggs, leaving the male to defend the nest. Research has shown the males increasingly become more invested in defending their nest as the young develop into sac-fry and then the amount of energy they expend rapidly decreases as the young become free-swimming (Cooke et al. 2002).
Here’s a video we shot of this smallmouth defending his nest.