Estimating Survival and Recruitment in a Freshwater Mussel Population Using Mark-recapture Techniques

We used a mark-recapture method and model averaging to estimate apparent survival, recruitment and rate of population growth in a native freshwater mussel population at a site on the Cacapon River, which is a tributary to the Potomac River. Over 2200 Elliptio complanata, E. fisheriana and Lampsilis cariosa were uniquely tagged over a period of 4 y. Recapture probabilities were higher in spring and summer than in winter except for L. cariosa which had a low probability of recapture regardless of time of year. All three species had high annual adult survival rates (>90%) with lower estimated survival of small ( less than or equal to 55 mm) mussels (43%-69%). The variation in apparent survival over time was similar for all three species. This suggests that whatever environmental variables affect survival of mussels in this site affected all three species the same. Recruitment rates were low (1-4%) for both E. complanata and L. cariosa, with E. fisheriana having several periods of high (15-23%) recruitment. Distribution within the site was affected by both downstream and upstream movement, though movement rates were generally