Restoration of Anadromous Alewife to Lakes of Connecticut

In the spring of 2014, the CT DEEP opened the final of three fishway on Mill Brook allowing anadromous alewife (river herring) access to historic spawning grounds in Rogers Lake. In Rogers Lake there was already a resident landlocked population. A decade of research on alewife in Rogers Lake and other lakes in the region has shown that anadromous and landlocked alewife differ in traits that strongly affect the ecology of lakes, including the duration in freshwater, gape width, gillraker spacing, prey size‐selectivity, diet composition, habitat usage, and whole‐body morphology (Palkovacs et al. 2008, Palkovacs and Post 2008, Schielke et al. 2011, Jones et al. 2013, Palkovacs et al. 2014). The fishway allowed for anadromous and landlocked alewife to come into "secondary contact," a process in which previously isolated and potentially divergent linages come back into contact. At the start of this project, the outcome of secondary contact between landlocked and anadromous alewife was uncertain. Landlocked alewife could outcompete and prevent establishment of anadromous alewife, anadromous alewife could establish a population that coexists with the landlocked population, or landlocked and anadromous alewife could hybridize in the lake. These potential outcomes would have important implications for anadromous alewife restoration efforts in CT and across the range of anadromous alewife. For example, a large locally adapted resident landlocked population might outcompete a small colonizing anadromous population, in which case additional management activities would be needed to facilitate anadromous alewife restoration. The outcomes of restoration and secondary contact could also have implications for the food webs and water quality of lake with existing landlocked populations and restored anadromous populations.