Can dietary reliance on Pacific salmon eggs create otolith Sr/Ca signatures that mimic anadromy in resident salmonids?
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Many aspects of the ecology, growth, life history, and population dynamics of fishes differ between anadromous populations and those residing exclusively in freshwater habitats. Analysis of the elemental composition of otoliths (ear stones) is commonly used to indicate the migration history of individuals, relying on the differences in ambient concentrations of calcium, strontium, and barium and their subsequent incorporation into calcified structures. Dietary contribution to otolith chemistry is often overlooked, but in this study we report results consistent with the possibility that reliance on food resources derived from the ocean via Pacific salmon can produce otolith Sr/Ca ratios suggesting anadromy in freshwater resident fish. Dolly Varden, Salvelinus malma, from the Iliamna River, Alaska feed very heavily on eggs and other tissues from sockeye salmon, Oncorhynchus nerka, and their otoliths had Sr/Ca ratios typical of fish making seasonal migrations to marine waters but the Ba/Ca ratios were consistent with residence in fresh water. Water samples from the river provided no indication that the elevated Sr concentrations came from the river. A simulation of otolith chemistry resulting from Sr incorporation from both water and diet across a range of published values in salmonids indicates that a diet of salmon eggs and tissues can produce marine Sr/Ca ratios while fish remain in fresh water. Without experimental evidence such as a controlled diet study these results are suggestive but not conclusive. Nevertheless, they send a cautionary note that in some cases heavy reliance on marine-derived food sources might affect otolith microchemistry, creating an appearance of anadromy in fish that did not leave fresh water.
KeywordsAnadromy Elemental analysis Microchemistry Migration Otolith Pacific salmon
This study was supported by the Alaska Department of Fish and Game Division of Sport Fish, and the H. Mason Keeler Endowment at the University of Washington, with permits from the AGF&G and University of Washington IACUC. We thank Cody Larson, Ian Fo and Craig Schwanke, among others, for assistance with field collections. Kathy Smikrud generously provided the map of sampling locations. Comments on earlier drafts and suggestions during the project’s development were provided by David Beauchamp, Keith Denton and Daniel Schindler (UW). We thank Randy Brown (U.S. Fish and Wildlife Service), Chris Zimmerman (U.S. Geological Service), and Jessica Miller (Oregon State University) for unpublished data, assistance with sample processing and interpretation, and comments on earlier versions of this manuscript. We also thank two anonymous reviewers for providing helpful advice that greatly improved the manuscript.
- Baker RR (1978) The evolutionary ecology of animal migration. Holmes and Meier, New YorkGoogle Scholar
- Jaecks TA (2010) Population dynamics and trophic ecology of Dolly Varden in the Iliamna River, Alaska: life history of freshwater fish relying on marine food subsidies. Master’s thesis. University of Washington, SeattleGoogle Scholar
- Kalish JM, Beamish RJ, Brothers EB, Casselman JM, Francis RICC, Mosegaard H, Panfili J, Prince ED, Thresher RE, Wilson CA, Wright PJ (1995) Glossary for otolith studies. In: Secor DH, Dean JM, Campana SE (eds) Recent developments in fish otolith research. University of South Carolina Press, Columbia, pp 723–729Google Scholar
- Matsuura H, Haraguchi H (2001) Multielement determination of major-to-ultratrace elements in salmon egg by ICP-AES and ICP-MS. Anal Sci 17(Suppl):975–978Google Scholar
- McDowall RM (1988) Diadromy in fishes. Timber Press, PortlandGoogle Scholar
- Northcote TG (1978) Migratory strategies and production in freshwater fishes. In: Gerking SD (ed) Ecology of freshwater fish production. John Wiley and Sons, New York, pp 326–359Google Scholar
- Rich HB Jr (2006) Effects of climate and density on the distribution, growth, and life history of juvenile sockeye salmon (Oncorhynchus nerka) in Iliamna Lake, Alaska. Master’s thesis. University of Washington, SeattleGoogle Scholar
- Tabouret H, Bareille G, Claverie F, Pecheyran C, Prouzet P, Donard OFX (2010) Simultaneous use of strontium:calcium and barium:calcium ratios in otoliths as markers of habitat: application to the European eel (Anguilla anguilla) in the Adour basin, South West France. Mar Environ Res 70:35–45CrossRefPubMedGoogle Scholar
- Toole CL, Nielsen RL (1992) Effects of microprobe precision on hypotheses related to otolith Sr/Ca ratios. Fish Bull 90:421–427Google Scholar
- Wells BK, Rieman BE, Clayton JL, Horan DL, Jones CM (2003) Relationships between water, otolith, and scale chemistries of westslope cutthroat trout from the Coeur d'Alene River, Idaho: The potential application of hard-part chemistry to describe movements in freshwater. Transactions of the American Fisheries Society 132(3):409–424Google Scholar
- Zimmerman CE, Nielsen RL (2003) Effect of analytical conditions in wavelength dispersive electron microprobe analysis on the measurement of strontium-to-calcium (Sr/Ca) ratios in otoliths of anadromous salmonids. Fish Bull 101:712–718Google Scholar