Effects of Asian Tapeworm on Mohave Tui Chub
USGS, NPS, California Fish and Game Department, St. Norbert's College
September 2002 to September 2007
Distribution of the introduced Asian tapeworm Bothriocephalus achelognathii in the southwestern United States is rapidly increasing. Reports from the mid 1980's first documented the tapeworm in fishes, most commonly cyprinids, of the Grand Canyon and associated tributaries. From 1995 to the present, the Asian tapeworm has appeared in other rivers in Utah, New Mexico, Nevada, Arizona, California, and Mexico. Despite the potential for this parasite to harm native fish populations and its explosive spread into new areas, very little is known about its effects on wild fish populations in the United States. The Asian tapeworm has been responsible for mass mortalities of fish in both cultured and wild populations in Europe. The tapeworm usually kills the host though blockage of the intestine or severe damage to the intestinal walls. Mortality of infected common carp in Russian ponds approached 90%. Cyprinids are the largest group of threatened and endangered fishes in both the Southwest and the United States. Cyprinid fishes are very susceptible to infection by the Asian tapeworm. Of those species exposed to Asian tapeworm in a southeastern United States study, small cyprinids living in warm waters had lowest survivorship. Most native cyprinids in the southwestern United States are small, and are living in small streams where water temperatures can be high. If the history of Asian tapeworm infestations in other areas repeats itself, mortality of cyprinids in many southwestern streams could be significant. We have three objectives for our study: (1) to examine the effects of the Asian tapeworm on the growth and survival of Mohave tui chub by themselves; (2) to examine the effects of the Asian tapeworm on the interactions between mosquitofish and Mohave tui chub; and (3) to examine the population dynamics of Asian tapeworm in Mohave tui chub inhabiting spring systems of the Mohave desert. This information will be useful not only to southwestern biologists, but others in North America facing potential Asian tapeworm infestations. These tests were conducted at the University of Arizona Agricultural Experiment Station. A final report was submitted and two articles were published on the subject, one with California Fish and Game and the other with the North American Journal of Aquatic Animal Health.