The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.
Gambuisa affinis can be distinguished from G. Boschung and Mayden suggest the following combination of characters:. Walters and Freeman recommend the follow combination of characters where each element is counted individually :.
Table 1. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Gambusia affinis are found here. Introduced mosquitofish have been particularly destructive in the American West where they have contributed to the elimination or decline of populations of federally endangered and threatened species Courtenay and Meffe Specific examples of their negative effects include a habitat shift and a reduction in numbers of the threatened Railroad Valley springfish Crenichthys baileyi in springs in Nevada Deacon et al.
Western Mosquitofish use the same habitat as the plains topminnow Fundulus sciadicus and have displaced these topminnows and other species with their aggressive behavior Whitmore The mosquitofish is also responsible for the elimination of the least chub Iotichthys phlegethontis in several areas of Utah Whitmore Meffe , found that mosquitofish are very aggressive, even toward larger fish.
They often attack, shred fins, and sometimes kill other species. Mosquitofish are known to prey on eggs, larvae, and juveniles of various fishes, including those of largemouth bass and common carp; they are also known to prey on adults of smaller species Meffe ; Courtenay and Meffe Courtenay and Meffe listed impacts on a variety of native fishes. Introducing mosquitofish also can precipitate algal blooms when the fish eat the zooplankton grazers Hurlbert et al.
