Gambusia holbrooki, Baird & Girard, 1859

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 765

Gambusia holbrooki

Common name. Eastern mosquitofish.

Diagnosis. Distinguished from other species of Poeciliidae in West Asia by: ● pelvic of male unmodified, tip of first ray not enlarged, similar in male and female / ● gonopodium long ● male dull grey / ● both sexes with rows of black spots in dorsal and caudal / ○ dorsal and caudal with black spots / ○ no blue or red blotches on flank in male / ○ dorsal origin far behind vertical of anal origin / ○ no lateral stripe / ○ male without sword-like prolongation on caudal. Size up to 30 mm SL in male, 55 mm in female.

Distribution . Introduced throughout warmer parts of West Asia, North Africa, and southern Europe. Throughout Mediterranean basin, including Nile and Cyprus. Locally in southern Caspian basin and coastal areas of Black Sea basin. Iran and locally in Saudi Arabia (Al-Ahsa oasis, Lake Alsfar, wadis around Riyadh). Native to North America, from Delaware drainage to Florida and Alabama.

Habitat. Still or slow-flowing waters, usually with dense aquatic vegetation. Can survive in heavily polluted waters by absorbing oxygen from top surface layers. Often, last fish survive in heavily polluted streams.

Biology. Matures at 4–6 weeks, three or more generations can be produced in a year. Breeds from April–October (depending on latitude), all year in south. Gestation lasts 3–4 weeks. Brood can be up to 354 young, usually between 40 and 60. Sexual activity ceases when temperatures drop below 18°C. While females continue to grow throughout their lives, males stop growing when they reach repro- ductive size. Feeds mainly on small aquatic invertebrates, highly opportunistic depending on prey availability. Lives below surface, catching prey at or just below surface.

Conservation status. Non-native; first introduced to Europe in Spain (1921) by health authorities in hope that it would control mosquitoes (vectors of various diseases). There is no evidence that it has had any effect on mosquito populations, but there is increasing evidence that it impacts native fish, seriously threatening many endemic species.

Remarks. Often referred to as G. affinis , a species identified by details of gonopodium morphology, 5½ dorsal rays (vs. 6½ in G. holbrooki ) and 8½ anal rays (vs. 9½). There are no confirmed records of G. affinis from West Asia. After the initial import in 1921, most subsequent introductions into Europe, North Africa, and West Asia were from European stocks. Still, Gambusia was also imported and introduced after 1921; at least one import was from the native range of G. affinis . Introduced populations in China are all G. affinis .

Furtherreading. Wootenetal.1988(genetics);Rauchenberger 1989 (phylogeny); Jenkins & Burkhead 1993 (biology); Doadrio 2001; Yoğurtçuoğlu & Ekmekçi 2017 (biology); Kurtul 2018 (biology and ecology); Kurtul & Sarı 2017 (risk potential); Kurtul & Sarı 2019 (distribution in Türkiye); Kurtul & Sarı 2020 (biology); Kurtul & Sarı 2021 (recognition level); Freyhof et al. 2020 (distribution in Saudi Arabia).

Figures

Gambusia holbrooki

Distribution