Abstract
The freshwater mussel, Cristaria plicata, is endangered in Tottori prefecture, and information on the population structure and reproduction of the species is necessary for conservation purposes. In the present study, the size structure of mussels, the presence of larval glochidia in females, fish fauna in mussel habitat, and the host suitability of their larvae were investigated in three remaining populations. Mussel size distribution in Tanegaike Pond was biased strongly toward larger individuals, indicating a lack of recruitment in this population in recent years. Although glochidia were observed in females during the reproductive season, the invasive predatory fishes Micropterus salmoides and Lepomis macrochirus were dominant in the pond, and predation on larval hosts by these invasive species is suggested to be a major factor inhibiting recruitment. In contrast, in other two ponds, smaller individuals were found together with larger animals. Invasive predatory fishes were not observed in these ponds, and the larval host Carassius spp. was dominant, indicating that these ponds were suitable for C. plicata recruits. These results suggest that the population dynamics of C. plicata strongly depend on fish communities and that the freshwater mussel population in Tanegaike Pond is endangered because of the dominance of invasive predatory fishes. We propose some future directions for the conservation of C. plicata populations in the Prefecture.
