Northwest Fisheries Science Center

Display All Information

Document Type: Journal Article
Center: NWFSC
Document ID: 1082
Title: The Use of Fatty Acid Analysis to Determine Species Dispersal: Caspian Terns in the Columbia River Basin
Author: C. Maranto, J. K. Parrish, D. P. Herman, A. E. Punt, Julian D. Olden, Michael T. Brett, Daniel D. Roby
Publication Year: 2011
Journal: Conservation Biology
Volume: 25
Issue: 4
Pages: 736-746
DOI: 10.1111/j.1523-1739.2011.01706.x
Keywords: source-sink, salmon, avian predator
Abstract: Understanding dispersal and source-sink dynamics is crucial in both ecology and conservation. Lethal control, which has been used as a tool to locally depress populations of animals in conflict with humans or endangered species, may counter intended management goals without consideration of animal movement. In open populations, localized lethal control may induce compensatory immigration, creating "attractive sinks." Within the Columbia River Basin, hydroelectric dams may represent attractive sinks because of their tendency to retard the out-migration of juvenile salmonids (Oncorhynchus spp.), attracting avian predators, the local abundance of which are then actively managed with a combination of non-lethal and lethal control. In 2001, over 900 Caspian terns (Hydroprogne caspia) were taken across mid-Columbia River dams. We used differences in fatty acid (FA) profiles of terns collected at coastal and inland breeding colonies to infer dispersal patterns. In particular, we modeled the rate of loss of FA marine biomarkers to infer whether and when terns foraging on dams had departed from the coast, and ultimately whether they could have bred at inland colonies. Multivariate analyses showed that coastal terns were differentiated by C20 and C22 mono-unsaturated FAs (MUFAs), whereas Potholes Reservoir terns were predominantly characterized by high levels of C18:3n3, C20:4n6, C22:5n3. Models of FA loss rates showed that a minimum of 56% of the terns collected at Rock Island Dam immigrated into the system from coastal sites. Because the coastal colony is orders of magnitude larger than any inland site, local lethal control at dams creates an attractive sink, and may impact regional population dynamics. We suggest that the use of FA biomarkers to monitor patterns of dispersal in animal populations can provide accurate and unique information, and may be extremely valuable in cases where source populations differ demonstrably in prey base.
Official Citation: Maranto CJ, Parrish JK, Herman DP, Punt AE, Olden JD, Brett MT, Roby DD. Use of Fatty Acid Analysis to Determine Dispersal of Caspian Terns in the Columbia River Basis, U.S.A. Conservation Biology 25(4):736-746.