The common bully (Gobiomorphus cotidianus) is endemic to New Zealand, a freshwater fish present throughout the country. There are three other bully species that can be confused with common bullies. Few characteristis in the common bully separate it from the other species. Vertical lines present on the cheek are a good defining characteristic along with the location of head pores and scale patterns on the head although these characteritics are hard to establish when seen in the wild. It is a amphidromous fish meaning it is able to survive in marine and fresh water environments. It is a small fish only growing as big as 15 cm. It can live in marine, fresh water or brackish water (fresh and salt water mixed) habitats and generally lives in benthic zones. Some populations venture into the sea