Stable Isotope Analysis in Fish Otoliths

Stable isotope analysis of fish otoliths has emerged as a powerful method for reconstructing environmental and physiological histories of individual fishes. Otoliths are accreted calcium carbonate structures in the inner ear, which record chemical signatures in growth increments. Ratios of stable oxygen and carbon isotopes within otolith carbonate reflect ambient water temperature, salinity, metabolic rate and dietary carbon sources. By analysing these isotope ratios with high spatial resolution, researchers can infer thermal habitats, migration pathways and energy expenditure across the full lifespan of a fish. This approach has broad applications in fisheries management, conservation biology and the study of climate impacts on aquatic ecosystems.

Research from Nature Portfolio

Recent studies have demonstrated that carbon isotopic composition in otolith carbonate offers a retrospective proxy for field metabolic rates in teleost fishes. Investigations of Atlantic cod have established a direct relationship between δ13C_otolith values and oxygen consumption, validated through laboratory and wild‐sample analyses. This metabolic proxy enables reconstruction of individual energy expenditure over lifetime scales, opening new avenues for physiological ecology in free‐ranging fish.

Stable Isotope Analysis in Fish Otoliths publication trend

The graph below shows the total number of articles in stable isotope analysis in fish otoliths across all publications each year (not limited to Nature Index journals).

Technical terms

Stable isotope analysis: Quantitative measurement of non‐radioactive isotope ratios in biological carbonates to infer environmental and metabolic histories.

Otolith: Incrementally growing calcium carbonate structure in a fish's inner ear that records chemical and physical conditions experienced over its lifespan.

δ18O_otolith: Expressed deviation of the 18O/16O ratio in otolith carbonate from a standard, primarily used to reconstruct water temperature.

δ13C_otolith: Expressed deviation of the 13C/12C ratio in otolith carbonate, reflecting metabolic and dietary carbon sources.

Isoscape: Spatial map of environmental isotope variation used to match tissue isotope values with geographic locations.

Fractionation equation: Mathematical relationship describing how isotopic ratios in otolith carbonate vary with temperature or other parameters.

References

1. Water temperature affects somatic growth, body condition and oxygen and carbon otolith isotopes of stout whiting (Sillago robusta). The Science of The Total Environment (2024).
2. Simple visualization of fish migration history based on high‐resolution otolith δ18O profiles and hydrodynamic models. Limnology and Oceanography Letters (2024).
3. Field metabolic rates of teleost fishes are recorded in otolith carbonate. Communications Biology (2019).
4. Field-based oxygen isotope fractionation for the conservation of imperilled fishes: an application with the threatened silver shiner Notropis photogenis. Endangered Species Research (2020).