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Marine Ecology Progress Series

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MEPS 598:167-185 (2018)  -  DOI:

Validation of otolith δ18O values as effective natural tags for shelf-scale geolocation of migrating fish

Audrey M. Darnaude1,2,*, Ewan Hunter2,3

1CNRS, UMR 9190 MARBEC, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier, France
2Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Lowestoft, Suffolk NR33 0HT, UK
3School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
*Corresponding author:
Advance View was available online November 29, 2017

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 δ18O 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 δ18O-based geolocation of fish during their annual migrations. Detailed intra-annual otolith δ18O measurements for 1997-1999 from individuals of 3 distinct sub-stocks with different spawning locations were compared with δ18O 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 δ18O values (-0.23 to 2.94‰) mainly reflected variation in temperature, and among-zone discrimination potential using otolith δ18O varied greatly by temporal scale and by time of year. Measured otolith δ18O values (-0.71 to 3.09‰) largely mirrored seasonally predicted values, but occasionally fell outside expected δ18O 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 δ18O. Comparing intra-annual δ18O 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 δ18O values can therefore provide relatively detailed fisheries-relevant data not readily obtained by conventional means.

KEY WORDS: Fish migration · Oxygen · Stable isotopes · Natural tag · Site fidelity · Plaice · Pleuronectes platessa

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Cite this article as: Darnaude AM, Hunter E (2018) Validation of otolith δ18O values as effective natural tags for shelf-scale geolocation of migrating fish. Mar Ecol Prog Ser 598:167-185.

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