Validation of otolith delta O-18 values as effective natural tags for shelf-scale geolocation of migrating fish

Abstract : The oxygen isotopic ratio of fish otoliths is increasingly used as a `natural tag' to assess provenance in migratory species, with the assumption that variations in delta O-18 values closely reflect individual ambient experience of temperature and/or salinity. We employed archival tag data and otoliths collected from a shelf-scale study of the spatial dynamics of North Sea plaice Pleuronectes platessa L., to examine the limits of otolith delta O-18-based geolocation of fish during their annual migrations. Detailed intra-annual otolith delta O-18 measurements for 1997-1999 from individuals of 3 distinct sub-stocks with different spawning locations were compared with delta O-18 values predicted at the monthly, seasonal and annual scales, using predicted sub-stock specific temperatures and salinities over the same years. Spatio-temporal variation in expected delta O-18 values (-0.23 to 2.94%) mainly reflected variation in temperature, and among-zone discrimination potential using otolith delta O-18 varied greatly by temporal scale and by time of year. Measured otolith delta O-18 values (-0.71 to 3.09%) largely mirrored seasonally predicted values, but occasionally fell outside expected delta O-18 ranges. Where mismatches were observed, differences among sub-stocks were consistently greater than predicted, suggesting that in plaice, differential sub-stock growth rates and physiological effects during oxygen fractionation enhance geolocation potential using otolith delta O-18. Comparing intra-annual delta O-18 values over several consecutive years for individuals with contrasted migratory patterns corroborated a high degree of feeding and spawning site fidelity irrespective of the sub-stock. Informed interpretation of otolith delta O-18 values can therefore provide relatively detailed fisheries-relevant data not readily obtained by conventional means.
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https://hal.umontpellier.fr/hal-02002357
Contributeur : Isabelle Vidal Ayouba <>
Soumis le : jeudi 31 janvier 2019 - 16:05:05
Dernière modification le : mardi 19 novembre 2019 - 17:08:02

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  • HAL Id : hal-02002357, version 1

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Audrey M. Darnaude, Ewan Hunter. Validation of otolith delta O-18 values as effective natural tags for shelf-scale geolocation of migrating fish. Marine Ecology Progress Series, Inter Research, 2018, 598, pp.167-185. ⟨hal-02002357⟩

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