Conservation Genetics of American Shad (Alosa sapidissima) and River Herring (Alosa aestivalis and Alosa pseudoharengus)
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By Eastern Ecological Science Center
November 25, 2024
USGS scientists are studying American shad (Alosa sapidissima), blueback herring (Alosa aestivalis), and alewife (Alosa pseudoharengus; collectively “alosines”) to develop robust genetic baselines that will inform management practices for individual species.
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What is the issue?
- Substantial resources have been invested to support the recovery of alosine populations, yet results have been mixed. For example, implementation of some fish passage projects to allow alosines better access to freshwater spawning areas has been associated with subsequent large increases in populations. However, other fish passage projects have not appeared to have a large positive effect, suggesting other factors beyond passage may be inhibiting recovery.
- Bycatch of alosines in other commercial fisheries is one potential factor which may be limiting the recovery of alosines.
- There is a critical need to be able to distinguish among populations or management units of alosines when individuals are found away from areas in which they originated. This information is needed to evaluate the impact of recovery investments focused on spawning population.
What’s at stake?
- American shad, blueback herring and alewife once supported large fisheries along the U.S. Atlantic Coast. However, impassable migration barriers, declines in habitat quality, and exploitation have led to declines in many spawning populations.
- Alosines are susceptible to fisheries bycatch (a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife) which can greatly reduce population size.
What is our approach?
- Together with our partners at Cornell University, we have developed single nucleotide polymorphisms (SNPs) and are using them to characterize the population genetics of American shad and provide decision-relevant information on the composition of both mixed stock aggregations and fisheries bycatch.
- Use genetic assignment testing to determine the source population of American shad, blueback herring, and alewife captured in marine environments.
- To help managers enhance recovery efforts for alosines, USGS will:
- Determine the population genetics of alosines at local, regional, and range-wide scales, including estimates of biodiversity, effective population size, and gene flow among populations.
- Assess patterns of diversity to identify populations that may be vulnerable (e.g., very small effective population size) or genetically diverse and thus potentially suitable as broodstock for restoration efforts.
- Continue collecting samples for its tissue repository to support ongoing studies of American shad and river herring species.
What are the benefits?
- An enhanced understanding of stock composition of alosines provides critical information on the status and trends of specific populations and offers much needed insight into how fisheries bycatch may be impacting recovery efforts.
- This study directly supports the needs of the Atlantic States Marine Fisheries Commission and its member states to effectively manage alosine populations across their ranges.
USGS scientists are studying American shad (Alosa sapidissima), blueback herring (Alosa aestivalis), and alewife (Alosa pseudoharengus; collectively “alosines”) to develop robust genetic baselines that will inform management practices for individual species.
Remote image Url
Sources/Usage: Public Domain. View Media Details
What is the issue?
- Substantial resources have been invested to support the recovery of alosine populations, yet results have been mixed. For example, implementation of some fish passage projects to allow alosines better access to freshwater spawning areas has been associated with subsequent large increases in populations. However, other fish passage projects have not appeared to have a large positive effect, suggesting other factors beyond passage may be inhibiting recovery.
- Bycatch of alosines in other commercial fisheries is one potential factor which may be limiting the recovery of alosines.
- There is a critical need to be able to distinguish among populations or management units of alosines when individuals are found away from areas in which they originated. This information is needed to evaluate the impact of recovery investments focused on spawning population.
What’s at stake?
- American shad, blueback herring and alewife once supported large fisheries along the U.S. Atlantic Coast. However, impassable migration barriers, declines in habitat quality, and exploitation have led to declines in many spawning populations.
- Alosines are susceptible to fisheries bycatch (a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife) which can greatly reduce population size.
What is our approach?
- Together with our partners at Cornell University, we have developed single nucleotide polymorphisms (SNPs) and are using them to characterize the population genetics of American shad and provide decision-relevant information on the composition of both mixed stock aggregations and fisheries bycatch.
- Use genetic assignment testing to determine the source population of American shad, blueback herring, and alewife captured in marine environments.
- To help managers enhance recovery efforts for alosines, USGS will:
- Determine the population genetics of alosines at local, regional, and range-wide scales, including estimates of biodiversity, effective population size, and gene flow among populations.
- Assess patterns of diversity to identify populations that may be vulnerable (e.g., very small effective population size) or genetically diverse and thus potentially suitable as broodstock for restoration efforts.
- Continue collecting samples for its tissue repository to support ongoing studies of American shad and river herring species.
What are the benefits?
- An enhanced understanding of stock composition of alosines provides critical information on the status and trends of specific populations and offers much needed insight into how fisheries bycatch may be impacting recovery efforts.
- This study directly supports the needs of the Atlantic States Marine Fisheries Commission and its member states to effectively manage alosine populations across their ranges.