Coastal River Connectivity and Shortnose Sturgeon: A Metapopulation Perspective

Although previously believed to remain within rivers, recent work has shown that shortnose sturgeon frequently move among coastal rivers such as the Penobscot and Kennebec in the Gulf of Maine. These movements include incursions into neighboring smaller coastal rivers. Because, most work thus far in the Gulf of Maine has focused on movements within systems, a paucity of information detailing local and regional scale factors influencing population dynamics exists. Our work focuses on determining the relative importance of coastal migrations and habitat use to the overall population viability of shortnose sturgeon within the Gulf of Maine. We continue to assess population connectivity with several techniques. Using standardized acoustic telemetry, we assessed immigration and emigration rates in conjunction with mark recapture methods within the Penobscot River to estimate population size. Moreover, observations of movements among systems were used to characterize the degree of connectivity between systems. Diet analyses and concurrent habitat surveys to be conducted will provide habitat use and habitat quality information. Additionally, elemental analyses of hard structures may prove useful in determining river of origin, thereby increasing our understanding of connectivity and source/sink dynamics in the region. The demographic information gained from diet and elemental analyses will contribute to understanding the influence of local scale drivers on connectivity. Our work has begun to address the relationship between, and influences of, local metapopulation patch dynamics and spatially larger regional dynamics on sturgeon populations in the Gulf of Maine. We hypothesize that coastal migrations of shortnose sturgeon in conjunction with demographic connectivity are important in maintaining population viability and expanding the metapopulation framework throughout the Gulf of Maine.