T. D. Levine1, B. K. Lang2, and D. J. Berg3.  Department of Zoology, Miami University, 1Oxford, OH 45056 and 3Hamilton, OH 45011.  2Conservation Services Division, New Mexico Department of Game and Fish, Santa Fe, NM 87507.


The obligate reliance of freshwater mussels on aquatic vertebrates as hosts of glochidia creates significant complications in understanding mussel life history and demography, and in development of effective conservation strategies.  The typical approach for identifying these hosts is via laboratory trials that identify potential host species, but do not reveal which of these species are actually used by mussel populations.  Laboratory trials identified 23 of 30 species as potential hosts for Popenaias popeii.  We conducted repeated surveys of fishes from the Black River, NM to determine which species were infested with P. popeii glochidia, and to measure the prevalence and intensity of infestations.  We calculated an “ecological host index” that integrates fish abundance with infestation prevalence and intensity.  Surveys collected 2,115 individuals from 14 species of fish; of these, 249 individuals of 14 species had encysted glochidia.  Three species of catostomids had relatively low-to-moderate abundance, moderate-to-high prevalence, and high intensity of infestations; one species of cyprinid had moderate abundance, high prevalence and high intensity.  All other species had low abundance or prevalence, and low intensity.  Carpiodes carpio, Moxostoma congestum, and Cyprinella lutrensis had much higher ecological host indices than any other species.  Infestations on benthic-dwelling catostomids were on the face and operculum, while those on the water-column-dwelling C. lutrensis were on the gills.  We conclude that the list of ecologically relevant host species is much smaller than the list of potential hosts identified in laboratory trials.  Successful conservation and restoration of unionid populations will require the presence of this much smaller set of host species.