Mark A. Pegg
Date of this Version
Ohlman, L. M. 2019. Population dynamics of the freshwater mussel Lampsilis cardium reintroduced in Nebraska. Master's thesis. University of Nebraska, Lincoln.
The global decline of native freshwater mussels has accelerated conservation projects that preserve and restore populations, but the complex life histories among species challenges biologists in determining the most effective management strategies. This study details the conservation of plain pocketbook, a Tier I threatened mussel species in Nebraska that was artificially propagated and reintroduced into 13 sites from autumn 2016 to summer 2017. The objectives of this study were: 1) determine how handling influences mussels, and 2) evaluate mussel growth and survival following introductions.
We conducted a laboratory experiment with age-2 plain pocketbook to assess the effects of handling on mussel growth and survival. We applied one of three handling rate treatments to experimental units for 12 weeks where mussels were handled up to 25 times. We compared end-of-study growth rates and survival among treatment and control group (i.e., no handling) mussels. Growth rates were unaffected by handling and no mortality occurred during the study, indicating plain pocketbook is tolerant of short-term repeated handling. We then conducted a mark-recapture study for introduced mussels to assess the relations of habitat, timing of introduction, and shell size to mussel growth and survival. We seasonally surveyed sites during 2017 and 2018 to collect habitat data and recapture tagged mussels. We used von Bertalanffy equations to model mussel growth among sites, introduction years, and streams. We used Cormack-Jolly-Seber models to estimate recapture and apparent survival rates of each site. We constructed cumulative daily survival curves and compared curves among sites, introduction years, and streams. We attributed growth differences to water temperatures relating to season of introduction. We determined mussels were at heightened risk for mortality during introduction and spring. We qualitatively linked these time periods to environmental stressors and used this information to identify suitable habitats for mussels and develop recommendations for further introductions.
Handling is an anthropogenic stressor for mussels that can be moderated through proper research and techniques. Short-term monitoring studies can provide valuable insight on the population dynamics of introduced freshwater mussels. Implications from this study have the ability to collectively enhance the management of this imperiled taxon.
Advisor: Mark A. Pegg