Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?

Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science
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Abstract

American shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density-dependent, deterministic, stage-based matrix model to predict the population-level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic-tagged adult American shad and oxytetracycline-marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out-migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density-dependent processes, and the impacts of structures to increase out-migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?
Series title Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science
DOI 10.1080/19425120.2012.675969
Volume 4
Issue 1
Year Published 2012
Language English
Publisher American Fisheries Society
Contributing office(s) Coop Res Unit Atlanta
Description 22 p.
First page 262
Last page 283
Country United States
State North Carolina, Virginia
Other Geospatial Roanoke River
Online Only (Y/N) N
Additional Online Files (Y/N) N