Parasites of Hawaiian Stream Fishes: Sources and Impacts

Introduced freshwater fishes impact native Hawaiian stream fishes in two important ways. In addition to direct negative effects associated factors such as predation, competition, and interference, indirect effects may occur when exotic fishes transfer their parasites to native hosts. Six species of helminths that have been introduced with alien live-bearing fishes, including guppies, green swordtails, shortfin mollies, and mosquitofish which now parasitize the five species of gobioids that occur naturally in Hawaiian streams. Some of these exotic parasites form large populations and produce heavy infections in native fishes that can result in disease. Sources, host specificity, distribution, and life cycles of these parasites were studied to assess their potential for pathogenicity and to aid in the formulation of comprehensive conservation and management plans for native stream species in Hawai‘i.