To stock or not to stock? Assessing restoration potential of a remnant American shad spawning run with hatchery supplementation

North American Journal of Fisheries Management
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Abstract

Hatchery supplementation has been widely used as a restoration technique for American Shad Alosa sapidissima on the East Coast of the USA, but results have been equivocal. In the Penobscot River, Maine, dam removals and other improvements to fish passage will likely reestablish access to the majority of this species’ historic spawning habitat. Additional efforts being considered include the stocking of larval American Shad. The decision about whether to stock a river system undergoing restoration should be made after evaluating the probability of natural recolonization and examining the costs and benefits of potentially accelerating recovery using a stocking program. However, appropriate evaluation can be confounded by a dearth of information about the starting population size and age structure of the remnant American Shad spawning run in the river. We used the Penobscot River as a case study to assess the theoretical sensitivity of recovery time to either scenario (stocking or not) by building a deterministic model of an American Shad population. This model is based on the best available estimates of size at age, fecundity, rate of iteroparity, and recruitment. Density dependence was imposed, such that the population reached a plateau at an arbitrary recovery goal of 633,000 spawning adults. Stocking had a strong accelerating effect on the time to modeled recovery (as measured by the time to reach 50% of the recovery goal) in the base model, but stocking had diminishing effects with larger population sizes. There is a diminishing return to stocking when the starting population is modestly increased. With a low starting population (a spawning run of 1,000), supplementation with 12 million larvae annually accelerated modeled recovery by 12 years. Only a 2-year acceleration was observed if the starting population was 15,000. Such a heuristic model may aid managers in assessing the costs and benefits of stocking by incorporating a structured decision framework.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title To stock or not to stock? Assessing restoration potential of a remnant American shad spawning run with hatchery supplementation
Series title North American Journal of Fisheries Management
DOI 10.1080/02755947.2013.763874
Volume 33
Issue 3
Year Published 2013
Language English
Publisher American Fisheries Society
Contributing office(s) Coop Res Unit Leetown
Description 9 p.
First page 459
Last page 467
Online Only (Y/N) N
Additional Online Files (Y/N) N
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