A Hierarchical Bayesian Approach for Estimating Freshwater Mussel Growth Based On Tag-Recapture Data

In fisheries stock assessment and management, mark-recapture survey is often used to collect individual growth information. However, some tagged animals can be recaptured more than one time in mark-recapture studies and ignorance of the autocorrelations for individual may result in substantial biases in growth parameters estimation. To investigate the existence of individual and sex variability in growth, we designed a mark-recapture survey for one endangered freshwater mussel species (oyster mussel) and one common, non-imperiled species (pheasantshell) by using a passive integrated transponder (PIT) technique. A model with individual and sex variability (M1), a sex-related difference model (M2), an individual variability model (M3) and a nonhierarchical model (M4) were developed to estimate the growth of oyster mussel and pheasantshell. Deviance information criterion (DIC) was used to measure the performance of these models. For oyster mussel, females tended to have higher means of asymptotic length (44.96 mm) and growth rate (0.283/year) than males (42.18 mm and 0.213/year). The model incorporating individual variability (M3) yielded the lowest DIC value for both species. Thus, we suggest that a hierarchical approach be used to consider individual variability for modeling growth of mussels with mark-recapture data, especially when there is a high percentage of multiple recaptures.