FRESHWATER – MARINE LINKAGES: THE ROLE OF SMALL COASTAL RIVER SYSTEMS AS A SOURCE OF FALL FORAGE FISH (RIVER HERRING) IN THE NEARSHORE MARINE ENVIRONMENT IN MAINE

Throughout their range, river herring (alewives and blueback herring) spawning runs are depressed. In Maine, river herring spawning runs are tiny in comparison to descriptions of historical runs in the 1700-1800s, where fish were harvested by the ship-hold. Decreases in these harvests have been attributed to the construction of innumerable small and large dams on nearly every coastal river and stream and, within the last 40 years, more efficient harvest methods in the marine environment. Today there is an unprecedented rate of dam removal and efforts to re-invigorate alewife runs in larger rivers. We will discuss these activities in the context of nearshore marine food webs and what may be missing from these food webs under current river herring production. Diet data collected from two Maine estuaries in 2007 and 2008 demonstrated that young-of-year (YOY) alewives can compose a large proportion of the diet of a diversity of predatory fishes when YOY alewives are abundant in the estuary and nearshore region. However, in 2007, alewives were only present during one 2 week period, suggesting that although alewife represent high-quality food late in the growing season, when juvenile and adult groundfish are in need of energy prior to the onset of winter, the resource is only available in short-lived pulses as YOY migrate out of freshwater nursery habitat. We argue that the limited number of river herring runs active today may be contributing to the pulse nature of this potentially important resource, and that in the past many runs from a diversity of freshwater systems may have resulted in what was effectively an extended out-migration period. This result argues for a regional approach to river herring restoration that takes into account the cumulative potential for YOY production.