Poeciliidae - Livebearers
The pike killifish's preferred habitat is along the banks of slow moving streams of mangrove (Rhizophora mangle) and reed (Phragmites communis) swamps and around inlets into salty bays (Connaly 1968). Turner and Snelson (1984) found this species reproducing in salinities from 0 to 35 ppt. In experimental food-habit studies, Miley (1978) found that the pike killifish feeds on native fishes and concluded that under certain conditions (scant cover for prey refugia and low water levels) it caused drastic reductions in densities of cyprinodonttids and poecilliids, particularly the mosquitofish (Gambusia holbrooki). It is not only a predator on smaller species or on young-of-year of larger species but competes with them for food. The species does not reach great densities where cover is sparse and large predators are present. Its establishment is of particular concern to mosquito-control personnel if chemical control has to be used to control the mosquitoes in the future. Some fishery biologists do not believe that mosquitofishes are effective control agents of mosquitoes, except in rare situations (Courtenay and Meffe 1989). Belshe (1961), Miley (1978), and Anderson (1981, 1982) conducted food-habit studies that revealed diet overlaps between this species and native species. Turner (1981) studied the population structure and reproduction of the pike killifish in Florida.
The pike killifish has been taken from several new localities in southern Florida, indicating its range expansion in recent years (W. F. Loftus, Biologist, Everglades National Park, National Biological Survey, personal communication).
Guppy (Poecilia reticulata). The guppy occurs naturally in the Netherlands, in the Antilles and Venezuelan islands, on Trinidad, in the Windward (Barbados) and Leeward (St. Thomas and Antigua) islands, and from western Venezuela to Guyana (Courtenay et al. 1984). The distribution of this species in the United States is presented by Courtenay et al. (1984). The widespread nature of the distribution of this species, especially in isolated warmwater springs, was probably due to dumped aquaria.
Courtenay et al. (1974) listed this species as established in Hillsborough and Palm Beach counties, Florida. It is not considered established now. Populations from Hillsborough County are probably not self-sustaining but escapees from local tropical-fish farms. The formerly established local population in Boca Raton, Palm Beach County, was exterminated when its habitat dried in the late 1970s. The guppy has also been collected in Dade County, but it is not believed to be established in this area (R. Robins, Professor of Fisheries, University of Miami, personal communication). Although some populations are in the immediate vicinities of fish farms, most populations in Florida seem to be ephemeral.
Green Swordtail (Xiphophorus helleri). The native range of the green swordtail is the Atlantic Slope of Middle America from the Rio Nautla, Veracruz, Mexico, to northwestern Honduras (Rosen 1960; Rosen and Kallman 1969). This popular aquarium fish was reported from Brevard County in Florida (Dial and Wainright 1983) but was not collected there in late 1983 or in 1984. Established populations in Florida seem to have escaped from local aquarium-fish farms (Courtenay et al. 1986). This species is considered to be stenohaline, requiring low salinities. At least two populations in eastern and southern Florida have persisted for several years and seem to be established locally.
The most probable pathway of introduction of this species depends on the location. Dumped aquaria and escaped or released individuals from fish farms are probable sources.
Southern Platyfish (Xiphophorus maculatus). Miller (1966) described the native range of this fish as the Atlantic Slope from just south of Ciudad Veracruz, Mexico, to northern Belize. It was reported as established in canals at Satellite Beach, Brevard County, and in some roadside ditches near Ruskin and perhaps elsewhere in Hillsborough County, Florida (Courtenay et al. 1974; Dial and Wainright 1983). Although formerly abundant in the Satellite Beach Civic Center pond, it has not been collected there since 1982 (Courtenay et al. 1984). The southern platyfish at Satellite Beach, Florida, was probably from a released aquarium. Individuals near Ruskin and Delray Beach, Florida, seem to have been escapees from nearby fish farms (Courtenay et al. 1986). The species has been collected from several localities in Florida in the last few years. Some sites are near fish farms; some individuals seem to have been dumped from aquariums. Some populations are considered locally established.
Variable Platyfish (Xiphophorus variatus). The variable platyfish is endemic to Mexico, occurring in southern Tamaulipas, eastern San Luis Potosi, and northern Veracruz (Rosen 1960). It has been reported as established in canals and roadside ditches of the eastern shore of Tampa Bay, Hillsborough County, Florida (Courtenay and Robins 1973; Courtenay et al. 1974). The current status of several of these populations is uncertain, although the formerly established population in ditches in Gibsonton, Hillsborough County, is no longer extant. Burgess et al. (1977) and we found established populations in Gainesville, Alachua County, Florida, on the campus of the University of Florida near a student dormitory and in a small stream near the center of town. The introductions are considered the result of dumped aquaria. There are also reports that the species was at one time a popular bait for black crappie (Pomoxis nigromaculatus). This species was recently taken near fish farms; some individuals seem to have been released by hobbyists. This species is considered locally established.
