Fish Hosts and Demographics and \u3cem\u3eLampsilis cariosa\u3c/em\u3e and \u3cem\u3eLeptodea ochracea\u3c/em\u3e, Two Threatened Freshwater Mussels in Maine

The yellow lampmussel (Lampsilis cariosa Say) and the tidewater mucket (Leptodea ochracea Say) are listed as threatened in Maine and are declining in their southern range. The fish hosts for both species are unknown, and no density or demographic data previously existed for populations in Maine. The goal of this study was to identify fish hosts for these two mussel species and examine population demographics of five populations in Maine to determine whether they were recruiting young. These species are primarily coastal in distribution, suggesting that the fish hosts may be diadromous. We tested yellow perch (Perca flavescens Michill), white perch (Morone Americana Gmelin), and pumpkinseed sunfish (Lepomis gibbosus Linnaeus) for suitability as a host for the yellow lampmussel. Transformed juvenile lampmussels were recovered from both yellow perch and white perch. We tested yellow perch, white perch, and alewife (Alosa pseudoharengus Wilson) for suitability as a host for the tidewater mucket. The tidewater mucket successfully transformed only on white perch, with none of the alewife surviving long enough for transformation to take place. Density and size distributions were determined at five sites in Maine using excavated 0.25m2 quadrats. Mean densities of yellow lampmussels ranged from 0.1/m2 to 1.6/m2. Individual yellow lampmussels ranged from 21 to 132mm in length. Mean densities of tidewater mucket ranged from 0/m2 to 0.3/m2, with individuals ranging in size from 28 to 102mm. Density estimates were also made for two common species found at almost all the study sites, Elliptio complanata (Gmelin) and Lampsilis radiata (Lightfoot) to compare their densities with those of the yellow lampmussel and tidewater mucket. E. complanata densities ranged from 0.4/m2 to 27.6/m2. Mean densities of L. radiata ranged from 0/m2 to 1.4/m2. Length at age relationships were examined using thin sections of relic valves from each site to examine recruitment and demography of the populations. All populations were found to have recent recruitment of young mussels (2-3 years old), as well as recruitment over the years. The maximum age of L. cariosa valves, determined by thin sectioning shells, was 18, whereas no L. ochracea relic valves exceeded ten years of age. The identification of fish hosts that are common, even invasive, suggests that the decline of these mussel species is not due to a lack of host fish, unless there is some other factor in the host/mussel relationship that was not examined in this study