Growth and longevity of two imperilled mussel species from the Edwards Plateau of Central Texas and its implications for freshwater mussel conservation and management

Authors: Michael de Moulpied, Clinton R. Robertson, Ryan Smith, Matthew Johnson, Adrienne M. Wootten, Elinor Martin, Roel Lopez, Charles R. Randklev

1. Life history information such as growth and longevity have been useful for understanding evolutionary relationships and predicting species responses to management and habitat alteration for aquatic species. For unionid mussels, which are globally imperilled, life history information remains unknown for a majority of unionid mussels and because of this has not been broadly used to guide mussel conservation efforts.
2. To address this knowledge gap, growth and longevity were estimated for Cyclonaias petrina, Texas pimpleback, and Lampsilis bracteata, Texas fatmucket, using thin-sectioning and validated using cross-dating. Both species are proposed for listing under the US Endangered Species Act.
3. Growth and longevity estimates differed between C. petrina (K = 0.065, 0.086, 0.101; L∞ = 55.03, 76.44, 94.43) and L. bracteata (K = 0.187, 0.208; L∞ = 61.40, 61.52), and growth for L. bracteata correlated to annual flow indices. Cross-dating revealed high interseries correlations (R = 0.400–0.573), indicating estimates can be viewed with some certainty.
4. Growth and longevity estimates indicate C. petrina is positioned near the K endpoint and L. bracteata near the r endpoint along the r/K life history continuum. This suggests C. petrina should be favoured in stable habitats where disturbance is minimal, whereas L. bracteata is expected to tolerate habitats with frequent and likely stochastic patterns of disturbance.
5. Knowledge of growth and longevity along with life history position provides a qualitative basis to help scientists and practitioners better anticipate how species will respond to environmental change and management actions. Given the conservation status of C. petrina and L. bracteata the life history findings from this study are timely and should be useful in their conservation.

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