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Marine Ecology Progress Series

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MEPS 433:195-204 (2011)  -  DOI:

Resolving natal tags using otolith geochemistry in an estuarine fish, rainbow smelt Osmerus mordax

Ian R. Bradbury1,4,*, Claudio DiBacco2, Simon R. Thorrold3, Paul V. R. Snelgrove4, Steven E. Campana2

1Fisheries and Oceans Canada, Science Branch, 80 East White Hills Road, PO Box 5667, St. John’s, Newfoundland and Labrador A1C 5X1, Canada
2Fisheries and Oceans Canada, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada
3Biology Department, MS #50, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
4Ocean Sciences Centre and Biology Department, Memorial University of Newfoundland, PO Box 4200, St. John’s, Newfoundland and Labrador A1C 5S7, Canada

ABSTRACT: Dispersal and connectivity are central to stability and persistence in natural populations. The use of otolith composition as geo-referenced tags may provide unparalleled resolution of spatial movements in marine and anadromous fish, although these geochemical signatures remain largely undescribed and the factors influencing otolith composition poorly understood. We examined spatial variation in the otolith geochemistry of juvenile rainbow smelt Osmerus mordax using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and isotope ratio monitoring mass spectrometry to evaluate its potential as a natural tag to resolve fine-scale geographic patterns and dispersal of estuarine early life history stages. Otolith element ratios (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) and isotope ratios (δ13C, δ18O, 87:86Sr) varied significantly among locations (n = 9) and provided 83% cross-validated accuracy using a quadratic discriminant function analysis. Assignments based only on the 3 isotope variables resulted in the highest rates of correct assignment (87%), largely driven by a significant increase (~11%) in correct assignments at nearby locations (<20 km distant). Five of the 7 elements examined were significantly correlated with each other, consistent with a common response to estuarine differences. We also observed a significant effect of habitat on assignment success, in that sites with partially restricted marine access (i.e. sand bars) assigned correctly at significantly higher rates. This study demonstrates that geochemical otolith signatures are intimately linked to estuarine structure, which in turn directly influences assignment power. It also demonstrates that assignment over fine spatial scales (<20 km) can be maximized by the examination of isotope signatures and sampling of specific habitat types.

KEY WORDS: Otolith chemistry · Rainbow smelt · Connectivity · Population structure · Elemental fingerprint

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Cite this article as: Bradbury IR, DiBacco C, Thorrold SR, Snelgrove PVR, Campana SE (2011) Resolving natal tags using otolith geochemistry in an estuarine fish, rainbow smelt Osmerus mordax. Mar Ecol Prog Ser 433:195-204.

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