Fishway efficiency and passage behaviour of Alewife in three fishways on Tantramar Marsh near Amherst, Nova Scotia
LE3 .A278 2014
Masters of Science
Alewives (Alosa pseudoharengus) are small anadromous river herring that move up coastal tributaries during an annual spring spawning migration. Over the last half century, dams and other riverine obstructions have severely restricted the access of alewives to their spawning grounds as well as impeding the movements of many other fish species both resident and migratory. In order to mitigate the effects of these barriers,thousands of fishways have been constructed, though how well such structures facilitate fish passage is still largely unknown. In this study, 1196 alewives were tracked though three different fishways (two Denil and one pool and weir) on the Tantramar Marsh nearAmherst Nova Scotia in order to evaluate the passage efficiency of the structures. Passage data revealed that fishways were size selective with larger fish being able to pass the structures more easily than smaller fish. Additionally it appeared that young immature fish may enter the river along with larger adults, but they may not seek out the fishways or complete the spawning migration. Fishway activity was also observed to be strongly diurnal with migratory alewives only entering the structures during periods of daylight; this included dawn and dusk. Questions of site fidelity were also raised during this study after the observation of river switching in migrants. Further data gathered suggested that the migratory period may range from 1-3 weeks depending on location and that migrant survival may be as high as 72-88% for spawning adults. River residency and attempts at fishway passage were also evaluated to determine possible behavioural effects on fishway passage efficiency.
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