Title: Taxonomic Identity and Relative Population Status of the Double-crested Cormorant in the Columbia River Estuary
Status:
Completed
Synopsis: The Double-crested Cormorant (DCCO; Phalacrocorax auritus) is a North American avian species that not long ago faced serious threats to its persistence primarily due to heavy contaminant loads picked up in their fish prey. Their remarkable recovery starting in the 1970's was primarily due to the banning of DDT and other contaminants. Recently, increased aquaculture and fisheries activities have resulted in an opposite effect (i.e., extreme population growth) in many locations. The Columbia River estuary is one of the areas that has experienced a population explosion of DCCO (P. a. albocilatus); East Sand Island supported 0 pairs of DCCO in 1977 whereas approximately 11,000 pairs nested there in 2003.
Management efforts for this species vary across North America depending on its local status and perceptions regarding its role as a nuisance species. For example, the extensive breeding population of DCCO in the Columbia River estuary is a concern relative to juvenile salmonid survival. An estimated 4.8 million juvenile salmonids were consumed by DCCO in 2003 during a period of good ocean productivity and thriving alternative prey populations. Their predation level on juvenile salmonids exceeded that of Caspian Terns (Sterna caspia) in 2003. Current management in the Columbia River estuary calls for reduction of Caspian Terns in order to reduce their take of juvenile salmonids. Substantial effort went into determining the regional status of the Caspian Tern population prior to initiating an Environmental Impact Statement on their management. Similarly, it is now important to determine the geographic boundaries and population status of the DCCO subspecies present in the estuary prior to initiating NEPA documentation and implementing appropriate management actions on this species.
One important aspect in beginning this examination of the effect of DCCO in the Columbia River is to understand its taxonomic identity and relative population status. This is be
Related Publications:
Mercer, D.M., 2008, Phylogeography and population genetic structure of double-crested cormorants (Phalacrocorax auritus)--M.S. Thesis: Corvallis, OR, Oregon State University, 101 p. [Highlight][FullText] Catalog No: 2158
Contact: Haig, Susan M. - Supervisory Research Wildlife Biologist Phone: 541-750-7482 Email: susan_haig@usgs.gov
