The bluegill bully (''Gobiomorphus hubbsi'') is a fish in the family

Eleotridae Eleotridae is a family of fish commonly known as sleeper gobies, with about 34 genera and 180 species. Most species are found in the tropical Indo-Pacific region, but there are also species in subtropical and temperate regions, warmer parts of t ...

that is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to New Zealand. It lives in shallow, fast-flowing riffles and torrents, where it forages and shelters amongst the gravels. It has a similar distribution to the other endemic riffle specialist, the

torrentfish The torrentfish (''Cheimarrichthys fosteri''), or panoko (Māori), is an amphidromous freshwater ray-finned fish that is endemic to New Zealand. Torrentfish are well adapted to life in shallow, fast-flowing riffles and rapids. They grow to a max ...

. It can be found up to inland, and from sea level up to an elevation of . The bluegill bully is the smallest of the Eleotrids, commonly reaching only . It is named for the bright blue edge to the operculum or gill cover, which is present in both sexes. It eats aquatic invertebrates and has an upturned mouth, allowing them to pick invertebrates off the stones above them. The species is

crepuscular In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal (active during dawn), vespertine (biology), vespertine/vespertinal (active during dusk), or both. This is distinguished from diurnalit ...

with the most active times for feeding at dawn and dusk. They feed predominantly on ''Deleatidium'' mayfly nymphs. They are

amphidromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

(meaning that they migrate from fresh water to the seas, or vice versa, but not for the purpose of breeding). The eggs are laid in fresh water and on hatching, the larvae are carried to sea for the first stage of their development. The larvae are at risk of being captured by irrigation schemes in some catchments, leading to high losses. It has been proposed that avoiding water abstraction in lower reaches of waterways in the hours post sunset could significantly improve survival of larvae. The young fish return to fresh water after a few months and continue to slowly migrate upstream as they get older. Thus the largest bluegills are found furthest upstream.

References

External links

Photograph of male
* Bluegill bully discussed on

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3 March 2023
{{DEFAULTSORT:Bluegill bully bluegill bully Endemic freshwater fish of New Zealand Taxa named by Gerald Stokell bluegill bully