Background/Question/Methods
Throughout their range, river herring (alewives and blueback herring) spawning runs are depressed. Nationally, the fishery has declined from 60 million pounds in the late 1960s to < 1.4 million pounds in 2006, prompting consideration of a national harvest closure on this once plentiful resource. 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 in the State of Maine there is an unprecedented rate of dam removal and efforts to re-invigorate alewife runs in larger rivers. However, less attention has been paid to the numerous runs that occur (or occurred) in smaller streams ranging in width from < 1 m to 10 m. In this paper we will review the current status of small alewife streams in coastal Maine as compared to published accounts of their status in the 1940s (Rounsefell and Stringer 1945) and discuss the importance of these runs to the nearshore marine food web in the context of diet data collected in 2006 and 2007.
Results/Conclusions
Diets 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. In our system, with fewer runs than in the 1940s, these alewives represent a pulse of high-quality food at a time when juvenile groundfish are near shore and need energy for over-wintering. However, because the timing of YOY alewife returns to the ocean appears to depend on system-specific factors, a diversity of local conditions across a range of rivers would have led, historically, to an extended out-migration period. Alewives would have been available as a forage fish for nearshore marine predators longer and in greater numbers than we see today.