Seven department fish ladders on six coastal rivers were operated during the spring of 2005 to facilitate the passage of river herring, American shad, and other diadromous fish over dams.
Estimated numbers of river herring monitored in 2005 were lower than in 2004 in all six rivers. This may be attributed to high flows in all monitored rivers during the river herring run. Record low returns at the Exeter and Taylor river ladders are of concern. Possible causes of low return numbers in the Exeter are low dissolved oxygen levels in the river, impediments to downstream migration, excessive harvest by the in-river fishery, or a combination of the three. Alewives constituted 100% of the returns in the Lamprey and Exeter rivers and dominated returns in the Cocheco and Winnicut rivers. River herring returns in the Oyster and Taylor rivers were exclusively blueback herring.
Confirmed returns of shad to the fishways were 12 in the Lamprey, three in the Exeter, and eight in the Cocheco rivers. The number of returns to the Exeter River decreased from 22 in 2004 to three in 2005. It is speculated that the reduction in returns could be due to water quality problems in the impoundment above the dam or incidental mortality in the in-river fishery for river herring. Biological samples indicated that ages ranged from III to VII and the ratio of males to females was three to one.
In a concerted effort between New Hampshire Fish and Game and the U.S. Fish and Wildlife Service (USFWS), approximately 3,200 river herring were transferred into impoundments or lakes in the Great Bay Estuary drainage to enhance spawning stocks. No American shad were stocked this year as low numbers at the Merrimack River fish lift prevented collection of gravid adults.
In addition, other collaborative efforts to restore anadromous fish to NH coastal rivers include dam removal or fish passage projects on three rivers within the Great Bay system. The first dam located at the head-of-tide on the Bellamy River was removed in 2004 to provide access to additional spawning and rearing habitat for species such as river herring and rainbow smelt. A feasibility study has recently been completed on fish passage options for the Winnicut River dam with dam removal and installation of a technical fishway at the next upstream barrier being chosen as the preferred option. Finally, a nature-like fishway has been selected as the preferred option for fish passage at Wiswall Dam on the Lamprey River and an Environmental Assessment for this project has been developed and approved.
NH Fish and Game, "Anadromous Fish Investigations, Year 2005" (2006). PREP Reports & Publications. 398.