Crans bully is another non-diadromous member of the Eleotridae family. They are stocky little fish that are hard to distinguish from common and upland bullies, whose distributions overlap that of Crans bully. On mature males, the top edge of the first dorsal fin is a bright pinkish-orange, but this is not a useful identification characteristic for small bullies and females.
Crans bully is strictly a North Island fish and is found in most areas. Its rarity in the arc northeast of Lake Taupo is thought to be a long-lasting effect of the Taupo eruption over 1800 years ago. As Crans bully has no marine phase, their ability to colonize new river systems is limited, and once they are gone from an area it is unlikely they will re-colonize on their own.
With no requirement to go to the sea, Crans bully is most common at sites at mid altitudes and some distance inland. It dwells in stony rivers and streams and does not establish lake populations. Breeding behaviour is similar to the other bullies, with the male establishing a territory, and remaining to guard the eggs after they are laid.