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Effect of dam removal on aquatic communities in the Salmon River, New York. Interim Report for 2010
John Cooper
Date Created and/or Issued
Contributing Institution
UC Riverside, Library, Water Resources Collections and Archives
Clearinghouse for Dam Removal Information (CDRI)
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Scope/Content: Abstract: Dam removal has become a major part of restoring aquatic communities to an approximation of the pre-disturbance condition. Phase 1 of this study (2002-2004) was designed to collect data on the aquatic community (defined here as sediment, macroinvertebrates, fish, unionid mussels, and aquatic plants) of the Salmon and Little Salmon rivers to evaluate the effects of removing the Fort Covington Dam. Additional fish data was obtained in 2008 and mussel data from 2005-2009. The dam was removed in 2009, nearly 100 years after construction, and opened about 22 km of river to migrating fishes. The opening of the dam lowered the reservoir water level by 47 cm over a 25-hr period and increased the water velocity from three to five times the previous rate, particularly between transects 3 and 5. This resulted in scouring of sediment, primarily sand, from just downstream of transect 7 through the former reservoir. The sediment was deposited from transect 3 downstream to transect 1 reaching a depth of 3 m at transects 1 and 2. The amount of redistributed sand was estimated to be 42,480 m3. Alteration of the habitats did not cause major changes in any of the macroinvertebrate indices although scouring of sand away from rocks on the east side of transect 2 and west side of transect 4 in 2010 resulted in an increase in mayfly and caddisfly families, most likely due to an increase in habitat complexity. Transect 4 also showed an increase in Total Families and decreased Percent Dominants and Percent Chironomids, all of which suggest an increase in diversity. The macroinvertebrate assemblage within the former reservoir remains much as it was prior to dam removal. Glide transects were dominated by midges (Chironomidae) while caddisflies, mayflies, riffle beetles, and midges were more abundant in riffle transects. The lowering of the water level in the reservoir stranded, and subsequently killed, 4 approximately 77% of the reservoir population of mussels in 2009, and this was reflected in a decline in mussel density at transect 5 in 2010. Deposition of sand in downstream areas buried an unknown number of mussels including two species, Lampsilis ovata and Lampsilis cariosa, considered to be in greatest conservation need by the New York Heritage Program. The abundance of these two species was estimated from shell middens and perhaps represented a dense mussel bed that is now covered by 3 m of sand. Total scores for the fish IBI declined in the Salmon River from 48 in 2002-2004 to 38 in 2010. The lower scores resulted from higher percentages of dominant species, omnivores, and insectivores. The total score for the Little Salmon River has varied between 40 and 44 for the three sampling periods of 2002-2004, 2008, and 2010. The IBI score was 'good' for the Salmon River and 'very good' for the Little Salmon River. Eastern sand darter (a threatened species in New York) was sixth in relative abundance and was collected in the main channel of the Salmon River and in the Little Salmon River. Eastern sand darter was not collected at Lewis Marina where it was abundant in 2004, perhaps due to increased silt and algae covering the former sand habitat. The abundance and distribution of aquatic plants did not change substantially since the 1930s in the Little Salmon River but nearly all submersed plants were either removed or buried in the Salmon River. The more abundant plant genera in the Little Salmon River were Potamogeton, Elodea, and Vallisneria. These plants provided the major nursery habitat for fish larvae and juveniles. The distribution of the exotic flowering rush (Butomus umbellatus) was similar to that in pre-dam removal years but the European frogbit Hydrocharis morsus-ranae, found in 2004, was no longer present.
Scope/Content: Dam type: concrete
Scope/Content: Reservoir size: 12 acre-feet. Height: 3 meters. Length: 27 meters.
Scope/Content: Date constructed: 1912. Date removed: 2009.
Ecology and river restoration
Dam retirement
Salmon, NY
Fort covington
Lat: 44 59 20; Long: 74 29 40

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