Shortnose Sturgeon

Ecological Risk Analysis for the Shortnose Sturgeon Populations in the Connecticut River

funded by
Electric Power Reasearch Institute and Northeast Utilities

Summary

        This project focused on two populations in the Connecticut River separated by the Holyoke Dam, with particular emphasis on the effects of migration on long-term survival. We developed a stage-based stochastic metapopulation model using RAMAS Metapop.  Based on the existing data, the model results suggested that the observed stability of the two populations is possible either with reproduction in both upper and lower populations and small to moderate rates of dispersal between them, or with no fecundity in the lower population, very high fecundity in the upper population and high rate of net downstream dispersal.  We also assessed the extinction risk of the two populations under various sets of assumptions, and explore the combinations of upper population fecundity and downstream migration that might compensate for lack of reproduction in the lower population.

        The results of the model demonstrate the type of questions that may be addressed with a modeling approach. However, the specific model predictions are not reliable due to a lack of data. To model the shortnose sturgeon populations of the Connecticut River, we made a number of assumptions, which could have an impact on the predictions. Our results suggest that large change in the fecundity and/or migration rates included in the model will have large effects on the long-term survival and final abundance of these shortnose sturgeon populations. This research, therefore, highlights three key areas for future research: (1) a better estimate of the annual fecundity its temporal variation in both the upper and lower populations, (2) a more accurate measurement of the rate of downstream movement, (3) estimates of annual survival rates, and their temporal variation, for ages less than 5 years.