Freshwater Fishes of Texas: A Field Guide

Livebearers—Family Poeciliidae

113 Western Mosquitofish Gambusia affinis (Baird and Girard, 1853) RANGE: Statewide. HABITAT: Ponds, lakes, and creeks in pools and backwaters. CHARACTERISTICS: (1) Mouth superior. (2) Dark suborbital bars. (3) Dorsal and lateral scales outlined with melanophores. (4) Dark middorsal stripe anterior to dorsal fin base. (5) Black specks on dorsal and lateral region; may be absent. (6) Thin, black midlateral stripe. (7) Lateral line absent; 29–32 lateral series scales. (8) Dorsal and caudal fins with 1–3 rows of black spots. (9) First few rays of anal fin elongate, males only (gonopodium). (10) Large, dark spot near anus, pregnant females only. DIMENSIONS: Up to 2.5 in (64 mm). FIN COUNTS: Anal soft fin rays 7; dorsal soft fin rays 6–7 (rarely 7); pectoral fin soft rays 12–14; pelvic soft fin rays 6. COLORATION: Head with dark suborbital bars. Dorsal region olive with middorsal stripe anterior to dorsal fin base and a few scattered small, black specks; lateral region silvery with thin, black midlateral line and scattered small, black specks; ventral region silvery. Dorsal and anal fins of mosquitofish have 1–3 rows of black spots. Dorsal and lateral scales outlined with melanophores. Livebearers—Family Poeciliidae Western mosquitofish, Gambusia affinis, female, 1.7 in (43 mm) 114 Big Bend Gambusia Gambusia gaigei Hubbs, 1929 RANGE: Springs east of Rio Grande village and Boquillas Crossing in Big Bend National Park. HABITAT: Spring headwaters. CHARACTERISTICS: (1) Dark suborbital bars may be absent. (2) Dorsal and upper lateral scales with melanophores forming crescent -shaped markings. (3) Dark middorsal stripe; may be absent. (4) Row of dark spots on lower third of dorsal fin; outer margin dark. (5) Dark midlateral stripe. (6) First few rays of anal fin elongate, males only (gonopodium). (7) Large, dark spot near anus, females only. DIMENSIONS: Up to 2.3 in (58 mm). FIN COUNTS: Dorsal soft fin rays 8. COLORATION: Head with dark suborbital bars. Dorsal region and lateral regions golden olive with melanophores forming crescent-shaped markings on scales; dark middorsal stripe; lateral region silvery with dark midlateral stripe; ventral region white. Large black spot near anus only on females. Row of dark spots on lower third of dorsal fin, with outer margin dark. COMMENTS: This species is listed by the state as endangered. Livebearers—Family Poeciliidae Big Bend gambusia , Gambusia gaigei, male, 1.8 in (46 mm) Big Bend gambusia , Gambusia gaigei, female, 1.5 in (38 mm) 11 largespring Gambusia Gambusia geiseri (Hubbs and Hubbs, 1957) RANGE: Headwaters of the San Marcos and Comal Rivers; introductions have placed it in the headwaters of the Concho River, San Solomon Springs, Leon Springs, and Independence Creek. HABITAT: Springs and rivers. CHARACTERISTICS: (1) Thin stripe of melanophores across lower lip. (2) Dark middorsal stripe anterior to dorsal fin base. (3) Scattered black specks on dorsal and lateral region. (4) Scale edges outlined with melanophores . (5) Dorsal and caudal fin with row of black spots, absent on juveniles; additional spots may form faint rows. (6) Thin, black midlateral stripe. (7) First few rays of anal fin elongate, males only (gonopodium). (8) Anal fin with median row of spots, females only. (9) Melanophores forming midventral line on caudal peduncle. DIMENSIONS: Up to 1.7 in (43 mm). FIN COUNTS: Dorsal soft fin rays 7–9. COLORATION: Lower jaw with a stripe of dark pigment. Dorsal region olive with middorsal stripe anterior to dorsal fin base and scattered black specks; lateral region silver with yellow and iridescent blue with thin, black midlateral stripe and scattered black specks. Dorsal and caudal fins with row of black spots absent on juveniles ; there may be additional spots forming faint rows. Melanophores form midventral line on caudal peduncle. Anal fin of females has a single row of black spots. COMMENTS: The largespring gambusia can be distinguished from the western mosquitofish by the stripe of dark pigment on the lower jaw and presence of a midventral stripe (both of which are absent on the western mosquitofish ) and by having only 7–9 dorsal fin rays versus 6 (rarely) or 7 dorsal fin rays on the western mosquitofish . Livebearers—Family Poeciliidae Largespring gambusia , Gambusia geiseri, 1.2 in (30 mm) 116 Pecos Gambusia Gambusia nobilis (Baird and Girard, 1853) RANGE: Headwaters of Phantom Lake Spring (Jeff Davis County); San Solomon, Giffen, and East Sandia Springs (Reeves County); and Leon Creek and Diamond Y Springs (Pecos County). HABITAT: Springs with vegetation. CHARACTERISTICS: (1...