bluegill bully

{{Short description|Species of fish}}

{{Use New Zealand English|date=July 2024}}

{{Speciesbox

| image = Male bluegill bully (Gobiomorphus hubbsi). Photo by Stella McQueen.png

| image_caption = Male bluegill bully

| status = VU

| status_system = IUCN3.1

| status_ref = {{cite iucn |author=Allibone, R. |author2=David, B. |author3=Franklin, P. |author4=Hitchmough, R. |author5=West, D. |author6=Ling, N. |author7=Crow, S. |date=2014 |title=Gobiomorphus hubbsi |volume=2014 |page=e.T197321A2482164 |doi=10.2305/IUCN.UK.2014-3.RLTS.T197321A2482164.en |access-date=19 November 2021}}

| taxon = Gobiomorphus hubbsi

| range_map = Gobiomorphus hubbsi - map.svg

| range_map_caption = Approximate known distribution of the bluegill bully on a map of New Zealand

| authority = (Stokell, 1959)

| synonyms =

• Philypnodon hubbsi Stokell, 1959

}}

The bluegill bully (Gobiomorphus hubbsi) is a fish in the family Eleotridae that is endemic 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.{{cite web|title=NIWA Fish Atlas - Bluegill Bully|url=https://www.niwa.co.nz/freshwater-and-estuaries/nzffd/NIWA-fish-atlas/fish-species/bluegill_bully|accessdate=1 December 2015|archive-date=8 December 2015|archive-url=https://web.archive.org/web/20151208145031/https://www.niwa.co.nz/freshwater-and-estuaries/nzffd/NIWA-fish-atlas/fish-species/bluegill_bully|url-status=live}} It can be found up to {{Convert|100|km}} inland, and from sea level up to an elevation of {{Convert|480|m}}.{{Cite web |last=McDowall |first=Bob |title=Freshwater fish - Bullies, smelt and grayling |url=https://teara.govt.nz/en/photograph/11120/bluegill-bully |access-date=5 March 2023 |website=Te Ara - the Encyclopedia of New Zealand |archive-date=20 January 2022 |archive-url=https://web.archive.org/web/20220120023017/https://teara.govt.nz/en/photograph/11120/bluegill-bully |url-status=live }} The bluegill bully is the smallest of the Eleotrids, commonly reaching only {{convert|60-70|mm|in|abbr=on}}.

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 with the most active times for feeding at dawn and dusk.{{Cite web |last=McEwan |first=Amber |date=30 April 2013 |title=The secret life of our bluegill bully |url=https://blog.forestandbird.org.nz/the-secret-life-of-our-bluefin-bully/ |access-date=2023-03-05 |website=Forest & Bird |language=en-US |archive-date=2023-01-27 |archive-url=https://web.archive.org/web/20230127162646/https://blog.forestandbird.org.nz/the-secret-life-of-our-bluefin-bully/ |url-status=live }} They feed predominantly on Deleatidium mayfly nymphs.{{Cite journal |last=Scrimgeour |first=G. J. |last2=Winterbourn |first2=M. J. |date=September 1987 |title=Diet, food resource partitioning and feeding periodicity of two riffle-dwelling fish species in a New Zealand river |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.1987.tb05238.x |journal=Journal of Fish Biology |language=en |volume=31 |issue=3 |pages=309–324 |doi=10.1111/j.1095-8649.1987.tb05238.x |issn=0022-1112}}

They are amphidromous (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.{{cite book|last1=McDowall|first1=R.M.|title=New Zealand Freshwater Fishes: A natural history and guide|date=1990|publisher=Heinemann Reed|location=Auckland|isbn=0 7900 0022 9}} 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.{{Cite journal |last=Jarvis |first=MG |last2=Closs |first2=GP |date=2015-10-02 |title=Larval drift of amphidromous Gobiomorphus spp. in a New Zealand coastal stream: a critical spatial and temporal window for protection |url=https://doi.org/10.1080/00288330.2015.1072569 |journal=New Zealand Journal of Marine and Freshwater Research |volume=49 |issue=4 |pages=439–447 |doi=10.1080/00288330.2015.1072569 |issn=0028-8330|doi-access=free }}

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.{{cite journal|last1=Atkinson|first1=N.K.|last2=Joy|first2=M.K.|title=Longitudinal size distributions of bluegill bullies (Gobiomorphus hubbsi) and torrentfish (Cheimarrichthys fosteri) in two large New Zealand rivers|journal=New Zealand Journal of Marine and Freshwater Research|date=2010|volume=43|issue=2|pages=643–651|doi=10.1080/00288330909510030|doi-access=free}}