Yucatán Gambusia

Yucatán Gambusia, Gambusia yucatana

The Yucatán Gambusia, Gambusia yucatana, whose common Spanish name is guayacón yucateco, is a species in the Livebearer or Poeciliidae Family, known collectively as topotes and espadas in Mexico. This fish is also known as mosquito fish or topminnow. Globally, there are forty-two species in the genus Gambusia, three of which are found in Mexican waters, all in the Atlantic.

The Yucatán Gambusias have moderately robust bodies that are somewhat compressed at the rear. They are light olive with large dark brown spots scattered in several rows on their sides. They have a dark bar under their eyes that does not extend into the gill cover. Their dorsal fin has one dominant row of dark spots with fainter rows of spots also present. Males have bright orange caudal fins with two or three rows of dark spots. Their head is robust and depressed with a small terminal slightly oblique mouth. They have a projecting lower jaw that opens at the front and is equipped with an outer row of large backward curved teeth and several rows of small pointed teeth. Their anal fin originates before the dorsal fin and has 10 or 11 rays; their caudal fin is rounded; their dorsal fin has a short base, is located near the rear of the body, and has 7 to 10 rays; and their pectoral fins are high on the body and originate in front of the pelvic fins whose fin tips become swollen in females. Their body is covered with large smooth scales.

The Yucatán Gambusias are a shallow fresh water species found at times in brackish waters of coastal lagoons at depths up to three feet. Females reach a maximum length of 8.0 cm (3.1 inches) and males measure 5.5 cm (2.2 inches). They spend the majority of their time on the water surface with their lower jaw projecting forward and upward allowing them to “gulp” air and skim microscopic matter from the water surface. They are preyed upon by numerous birds and fish including needlefish. Reproduction is viviparous with young born live.

In Mexico waters the Yucatán Gambusia have a limited distribution being limited to the fresh water drainage system of the Yucatán Peninsula.

The Yucatán Gambusia is most likely confused with the Caribbean Gambusia, Gambusia puncticulata (dark stripe under eyes) and the Pike Killifish, Telonesox belizanus (extended pointed snout; prominent spot at base of caudal fin).

There is currently an expanded effort to use Gambusias to control mosquitos as they eat mosquito larvae. They are currently being breed in Acapulco, Guerrero, and along the Pacific Coast with fish given to families to use in their rainwater collection barrels, buckets, and tubs where water is stored. As such they have become invasive in some areas. They are also used extensively in the aquarium trade.

Yucatán Gambusia, Gambusia yucatana. Fish caught out of a fresh water pond at the Vidanta Grand Luxxe Resort, Playa del Carmen, Quintana Roo, February 2016. Length: 5.1 cm (2.0 inches). Catch, identification, and photo courtesy of George Brinkman, Guelph, Ontario, Canada.