Species Regional Summary
Alosa sapidissima
Columbia River ( P260 )

Invasion History Vectors Impacts References

Invasion

Invasion Description

1st Record: OR-WA/Columbia River (1880, Chapman 1942, Lampman 1946)

Geographic Extent

OR-WA/Columbia River (1880, Chapman 1942, Lampman 1946); Crimms Island (downriver from Longview WA/OR/Columbia River (Haskell and Tiffin 2011); Albany/OR/Willamette River (1880, Chapman 1942, Lampman 1946); Astoria to the Cascades, 240 km upstream/OR/Columbia River (1896) (Chapman 1942; Lampman 1946; Sol et al. 2021); Granite Dam/ID/ Snake River, 600 km from the Ocean (Pearcy and Fisher 2011)

Vectors

Level Vector
Probable Fisheries Accidental (not Oyster)

Regional Impacts

Ecological ImpactCompetition
Zooplankton predation by American Shad are expected to affect food availability for native fishes, including Pacific salmon (Oncohrynchus spp.) (Haskell et al. 2013).
 
Ecological ImpactPredation
The increased population of American Shad in reservoirs of the Columbia River appears to have altered the zooplankton population, reducing the abundance of large zooplankton such as Daphnia spp. American Shad are estimated to consume an average of 23% of daily zooplankton production (Haskell et al. 2013).
 
Ecological ImpactParasite/Predator Vector
The increased population of American Shad in reservoirs of the Columbia River appears to have amplified the population of a native protistan parasite, Ichthyophonus spp. in freshwater reservoirs of the river. The parasite is regarded as a threat to native Pacific salmon, although prevalence was very low (~4%) in spring Chinook Salmon (Hershberger et al. 2010).
 
Economic ImpactFisheries
'Several hundred thousand shad are landed annually by commercial and sport fisheries in the Columbia River (Petersen et al. 2003', cited by Pearcy and Fisher 2011).
 
Ecological ImpactTrophic Cascade
Migration by American Shad has partially replaced the transport by native Salmon of nutrients (N and P) from the marine environment to the Columbia River Basin. At present, shad import 2% of the total phosphorus load to the John Day Reservoir, on the lower Columbia. Nutrient imports by shad roughly equal those of native salmon at present, but are much smaller than those from historic salmon population (Haskell 2018).
 

References

Full Reference List for Alosa sapidissima

  • Nemesis (current)
  • Marine Invasions Lab
  • Partner Portals
    Nemesis California Panama Galapagos Cocos Island NP JTMD
    Archived Projects
    Chesapeake
  • Browse Species
    Taxonomic Groups All Species
  • Browse Regions
    States
    Alaska
    Bioregions & Bays
  • News
  • login

Direct questions and comments to nemesis@si.edu.

©