Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Abstract

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified.

Prolonged estuarine habitat use by dusky grouper Epinephelus marginatus at subtropical latitudes revealed by otolith microchemistry

“…A better understanding of habitat use patterns of marine fish populations is vital to evaluate their dynamics and resilience to harvest, ultimately supporting adequate management and conservation measures (Andrello et al 2014, Davoren et al 2015. This fundamental aspect of fish life history can be revealed through the evaluation of natural markers such as otolith microchemistry (Rooker et al 2008, Reis-Santos et al 2013a, Darnaude et al 2014, as detailed analysis of the chemical composition of otoliths allows reconstruction of the environmental conditions experienced by individual fish throughout their entire life history (Campana 1999, Elsdon et al 2008, Tanner et al 2013. In general, strontium (Sr) and barium (Ba) concentrations in otoliths have a positive correlation with salinity and freshwater, respectively (Elsdon & Gillanders 2005, Sturrock et al 2012, Reis-Santos et al 2013b).…”

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

“…Intact otoliths were returned along with the archival tags for 83 fish, amongst which individuals with data records ≥3 mo were released and recaptured mainly between 1997 and 1999 (Darnaude et al 2014). Consequently, we chose these 3 successive years to reconstruct multi-annual environmental conditions prevailing over the full observed distribution range to compare with the seasonal δ…”

“…The small , while in b, coloured arrows show migration routes typical of each sub-stock (Fig. 1b modified from Darnaude et al 2014) proportion of plaice from sub-stock C that spawn in the English Channel (EC) do so only in December or in January, spending the remainder of the winter in the Southern North Sea (SNS) ). There, they mix with the individuals of the same substock that spawn in the SNS (mainly in January), but also with fish of sub-stocks A and B that also spawn in this area (in February and March).…”

“…O signatures laid down simultaneously in the otoliths of 24 tagged fish, from 3 'sub-stocks' that have discrete distributions for most of the year (Darnaude et al 2014). Comparison between measured and expected δ…”

Comparative Diagenesis and Rare Earth Element Variation in Miocene Invertebrate and Vertebrate Fossils from Panama

“…The crystal structure of otolith aragonite is cryptocrystalline, that is, although difficult to determine with X-ray diffraction (XRD), this structure can be observed under high magnification. Like many invertebrates, otoliths grow incrementally and, in conjunction with stable isotopes, have been used to understand ancient and modern ecology (e.g., Francillon-Vieillot et al 1990;Patterson et al 1993;Darnaude et al 2014).…”