| Summary: | Estuaries provide many ecosystem services such as buffering the negative impacts of storms, offering recreation and commercial fishing opportunities, and they serve as a critical habitat corridor for migratory fish. In New England, estuarine habitats have been dramatically altered over the last 200 years due to dam construction; migratory fish such as Atlantic salmon and alewives have suffered. While the beneficial effects of dam removal on migratory fish is well documented, less information exists on how dam removal and fish restoration affect nearshore prey communities. Here, we present data on abundance, diversity, and community composition of zooplankton in the Penobscot estuary following two dam removals. We couple this information with results from fish diet analysis to better understand the importance of fish predation on estuarine zooplankton communities. Our field surveys reveal zooplankton abundances being driven by changes in temperature and turbidity. Zooplankton community composition varied on both temporal and spatial scales and were strongly affected by temperature, dissolved oxygen, and juvenile river herring abundances. Juvenile alewives show distinct preferences for Eurytemora spp. and barnacle cyprids and nauplii. River herring may affect zooplankton community composition through selective feeding, but they do not appear to have impacted zooplankton abundances even as return of adult river herring numbers have increased exponentially as a result of dam removals and stocking.
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