Nesting begins in spring when water reaches roughly the mid-teens Celsius. The male sweeps a shallow depression in gravel with his tail, courts one or more females onto it, and then takes sole charge. He fans the eggs to keep silt off and water moving, and attacks anything approaching, including fish far larger than himself.
Guarding continues after hatching. The fry rise from the gravel as a dark cloud and stay near the nest for a period during which the male continues to escort them. Removing the guarding male reliably results in the nest being consumed by egg predators within a short time, which is why some fisheries agencies delay or restrict bass angling during the nesting season: a male caught and released may return too late.
How much a temporary removal actually costs a nest under varying predator densities is debated, and management responses across jurisdictions differ accordingly.