The common bully (Gobiomorphus cotidianus) is everywhere in New Zealand. It lives in rivers and streams near the coast and land-locked lakes. In rivers and streams, it mainly inhabits still or slow-flowing water. It is an important prey species for other fish, including eels.
Eggs are laid on the undersides of hard substrates (wood, rock) in lakes and rivers, and the developing eggs are defended by the male.
Acknowledgement: Mike Dickinson, Creative Commons 4.0