A Mark-Recapture Study: Measuring Growth and Respiration of a Freshwater Mussel in Massachusetts, USA

Eastern Pearlshell mussels (Margaritifera margaritifera) are a globally declining species that require clean cold streams and salmonid fish hosts. Little is known about movement and growth of this species in field conditions. Mark-recapture techniques were used to understand growth, abundance, and survival of M. margaritifera in the Quinapoxet River, Massachusetts, USA. Initial mussel captures were double-tagged and length was measured. Recaptured mussels were also measured to track growth. Dissolved oxygen uptake was used to measure individual mussel respiration rates under a range of water temperatures. It was expected that mussel respiration would be positively correlated with temperature, potentially leading to less available energy for growth. However, increased temperatures could also increase growth by lengthening the growing season. Of the 243 mussels captured in the two-year sampling period, 188 were initial captures and 25 were captured in both years. Mussels < 60 mm in length made up 11.2% of the sample and mussels > 90 mm made up 60.4% of the sample. Results showed a growth rate of 1.77 mm year^-1 ± 1.01 (mean ± 95% CI). On average, mussels moved upstream 0.31 m year^-1 ± 0.53. Growth was not significantly related to body size (slope = -0.07 ± 0.08, p-value = 0.07). With one outlier excluded, the relationship between growth and body size showed a significant relationship (slope = -0.11 ± 0.05, p-value = <0.001). Mark-recapture work will continue in future years to better estimate recruitment and survival using the Robust Design as well as individual growth rates as a function of body size and temperature.