Document Type



Aquaculture and Fisheries | Ecology and Evolutionary Biology | Population Biology | Terrestrial and Aquatic Ecology | Zoology


Alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) occur in anadromous populations that have a largely overlapping distribution from Florida to Newfoundland (Loesch 1987). Anadromous populations of these species are commonly collectively referred to as “river herring”. Adults inhabit coastal shelf waters until sexual maturity is reached at age 3-5 (Neves 1981). Sexually mature individuals make spawning migrations, commonly referred to as “runs”, into freshwater systems during spring months (Loesch 1987). Spawners can survive and return to spawn in subsequent years (Mullen et al. 1986). Juveniles reside in freshwater for 3-7 months, at which time they undertake a gradual migration to estuarine and marine waters (Loesch 1987).

Many freshwater systems within the State of Connecticut support river herring runs. These fish have historically been taken for use as bait by recreational anglers in Connecticut waters. These species also have ecological significance. Throughout all phases of their life cycle, river herring provide an important source of forage for a wide variety of predators (Loesch 1987). River herring runs can also serve as a vector for nutrient transport from the marine environment to freshwater systems (Durbin et al. 1979). There is also evidence that the seasonal presence of river herring in freshwater systems may benefit sport-fish species (McCaig 1980; Yako et al. 2000).

There is compelling evidence that river herring populations in Connecticut are declining. Annual passage of blueback herring at Holyoke Dam on the Connecticut River has declined three orders of magnitude over the previous 15 years (Savoy and Crecco 2004). Available data from other sites in Connecticut provide strong evidence of declines in the majority of streams surveyed, with the worst declines being noted in large river watersheds (Gephard et al. 2004). In response to these declines, an emergency fishery closure for inland waters was instituted by the Connecticut Department of Environmental Protection (CDEP) in 2001; this closure is still in effect.

The purposes of this project were to assess river herring population structure at study sites within Connecticut, make inter-watershed and temporal comparisons of population structure, and develop quantitative sampling strategies for estimation of river herring run size. Current data on population structure of river herring in Connecticut are largely unavailable. Collection of these data is crucial to the development of management strategies for amelioration of current population declines and will serve as valuable baseline data for future managers. Comparisons of contemporary population structure data to historic data will help to characterize decade-scale temporal shifts in population structure. Inter-watershed comparisons of population structure data may provide insight into processes driving the disproportionately precipitous declines within large river watersheds. Quantitative estimates of abundance are not available for many runs in Connecticut due to the prohibitive amount of cost and effort required to perform a census. Assessment of candidate quantitative sampling strategies will elucidate levels of sampling effort at which reasonably accurate and precise estimates of run size can be obtained.