Migratory Fish

How have migratory fish returns to the Piscataqua Region changed over time?

Overall migratory river herring returns to the Great Bay Estuary increased 69% between 2012 and 2016, however river herring returns have sharply declined for the Oyster and Taylor Rivers. Returns for American shad have been consistently fewer than five since 2011 and zero were reported in 2016. There are no statistically significant trends. A lack of fishable ice resulted in insufficient data for Rainbow Smelt in 2012, 2013, and 2016.


Migratory fish–such as river herring and American Shad–travel from ocean waters to freshwater streams, marshes, and ponds to reproduce. River herring are an important source of food for wildlife and bait for commercial and recreational fisheries.
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Observed river herring returns to the coastal rivers of the Great Bay Estuary varied during the 1972-2016 period (Figure 16.1). Total river herring returning to fish ladders in 2016 reached 199,090. This is a 69% increase from 2012 that was driven by record river herring returns in the Lamprey and Cocheco rivers. Conversely, returns have sharply declined in two other rivers: the Taylor and the Oyster. Due to variability in the dataset there are no statistically significant trends. Declines in river herring returns in some rivers may be due to several factors including: limited freshwater habitat quantity and quality, difficulty navigating fish ladders, safe downstream passage over dams, fishing mortality, pollution, predation, and flood events during upstream migrations. To continue improving river herring returns, NH Fish and Game and the NH Coastal Program continue to work with state, federal, and local partners on dam removal and culvert replacement projects on the Cocheco River (Gonic dams in Rochester), Bellamy River (Sawyer Mill dams in Dover), and Exeter River (Great Dam in Exeter; completed in September 2016).54, 55

Despite increases in river herring returns for some rivers, the Oyster and Taylor River populations have declined dramatically in recent years most likely due to poor water quality in impoundments upstream.56 Additionally the Winnicut River fish ladder has been declared ineffective and NH Fish and Game is working on a solution.57 The 2016 river herring returns are almost exclusively from the Lamprey and Cocheco Rivers.

Figure 16.1 Returns of river herring to NH coastal tributaries 1976-2016. In 2016 river herring returns were almost exclusively from two rivers: the Lamprey and Cocheco.