Fractal analysis of otolith contours and shape for marine fish species discrimination

Fernando Condal; Giulia Guida

doi:10.29103/joms.v3i1.24159

Authors

Fernando Condal Departament de Biologia i Geologia. Institut Angeleta Ferrer i Sensat, Sant Cugat del Vallès, Barcelona, c/Granollers 43, 08173 Sant Cugat del Vallès, Spain https://orcid.org/0000-0002-7296-0225
Giulia Guida Dipartimento di Ingegneria Civile e Ingegneria Informatica (DICII). Università degli Studi di Roma Tor Vergata. Via del Politecnico,1. 00133 Rome, Italy https://orcid.org/0000-0003-1129-7906

DOI:

https://doi.org/10.29103/joms.v3i1.24159

Keywords:

Otolith morphology, fractal geometry , species discrimination, fisheries science, Merluccius merluccius, contour analysis, ecomorphology

Abstract

Otolith morphology serves as a powerful tool for species discrimination and ecological studies, yet traditional morphometric approaches often overlook the functionally significant complexity of otolith contours. Here, we apply fractal geometry to analyse 184 sagittal otoliths from five ecologically diverse marine fishes (Merluccius merluccius, Phycis blennoides, Gadus morhua, Lophius piscatorius, and Trachinus araneus) collected from NW Atlantic and Mediterranean waters. Using the Guida et al. (2020) method, we quantified three morphological descriptors: fractal dimension (Df, roughness), circularity (M), and angularity (m). Our results revealed distinct species-specific morpho-spaces. The demersal M. merluccius exhibited the highest contour complexity (Df = 1.06 ± 0.03) and elongation (M = 0.64 ± 0.03), while the other species displayed smoother, more circular otoliths. The strong negative Df-M correlation reflects an evolutionary trade-off between sensory adaptation and hydrodynamic efficiency. These findings establish fractal otolith analysis as an effective taxonomic tool and a window into ecological specialization, with direct applications for fisheries management, paleo-ecological reconstructions, and climate change monitoring in marine ecosystems.

Downloads

Download data is not yet available.

References

Avigliano, E., Alvarez, N., & Volpedo, A. V. (2023). Otolith shape and elemental composition as complementary tools for discriminating Ethmalosa fimbriata stocks in the area of Africa's second largest river estuary. Fisheries Research, 257, 106489. https://doi.org/10.1016/j.fishres.2022.106489.

Borges, C., Gordo, L., & Costa, J. L. (2024). Integrating machine learning and otolith morphometrics for automated species identification. Fisheries Research, 270, 106945. https://doi.org/10.1016/j.fishres.2023.106945.

Campana, S. E. (1992). Otolith microstructure examination and analysis (pp. 73–100). In D. K. Stevenson (Ed.). Department of Fisheries and Oceans..

Campana, S. E. (2005). Otolith science entering the 21st century. Marine and Freshwater Research, 56(5), 485–495. https://doi.org/10.1071/MF04147.

Froese, R., & Pauly, D. (Eds.). (2011). FishBase. World Wide Web electronic publication, version 2(2011), 14. https://www.fishbase.se/search.php.

Gaylord, B., Kroeker, K. J., Sunday, J. M., Anderson, K. M., Barry, J. P., Brown, N. E., ... & Harley, C. D. (2015). Ocean acidification through the lens of ecological theory. Ecology, 96(1), 3–15. https://doi.org/10.1890/14-0802.1.

Guida, G., Casini, F., & Viggiani, G. M. (2017). Contour fractal analysis of grains. In EPJ Web of Conferences (Vol. 140, p. 05008). EDP Sciences. https://doi.org/10.1051/epjconf/201714005008.

Guida, G., Viggiani, G. M., & Casini, F. (2020). Multi-scale morphological descriptors from the fractal analysis of particle contour. Acta Geotechnica, 15(5), 1067–1080. https://doi.org/10.1007/s11440-019-00873-1.

Guida, G. (2023). giuliaguida00/fractal_analysis: Fractal analysis of contours (v1.0.0) [Computer software]. Zenodo. https://doi.org/10.5281/zenodo.7501952.

Hüssy, K., Mosegaard, H., & Jessen, F. (2020). Effect of age and temperature on amino acid composition and the content of different protein types of juvenile Atlantic cod (Gadus morhua) otoliths. Canadian Journal of Fisheries and Aquatic Sciences, 77(6), 1055–1063. https://doi.org/10.1139/cjfas-2019-0222.

Lauchlan, S. S., Nagelkerken, I., & Connolly, S. R. (2024). Otolith morphometrics as bioindicators of climate change impacts: A global meta-analysis. Global Change Biology, 30(1), e17102. https://doi.org/10.1111/gcb.17102.

Lombarte, A., & Cruz, A. (2007). Otolith size trends in marine fish communities. Marine Ecology Progress Series, 340, 255–265. https://doi.org/10.3354/meps340255.

Lombarte, A., Matić-Skoko, S., & Kruschel, C. (2023). Otolith phenotypic diversity as a tool for species identification and stock discrimination in Trachurus species. ICES Journal of Marine Science, 80(5), 1450–1462. https://doi.org/10.1093/icesjms/fsad073.

Manjabacas, A., Chic, Ò., García-Ladona, E., Tuset, V. M., Morros, J. R., Sayrol, E., ... & Lombarte, A. (2025). Twenty years of AFORO: New developments and connections enhancing otolith research. Fisheries Research, 281, 107242. https://doi.org/10.1016/j.fishres.2024.107242.

Martinez, C. M., Rutenberg, E. K., & Frederich, B. (2023). Otolith shape reflects swimming activity and habitat complexity in marine teleosts. Functional Ecology, 37(5), 1245–1257. https://doi.org/10.1111/1365-2435.14289.

Matić-Skoko, S., Peharda, M., Vrdoljak, D., Uvanović, H., & Markulin, K. (2020). Fish and sclerochronology research in the Mediterranean: Challenges and opportunities for reconstructing environmental changes. Frontiers in Marine Science, 7, 195. https://doi.org/10.3389/fmars.2020.00195.

Morales-Nin, B. (1987). Métodos de determinación de la edad en los osteictios en base a estructuras de crecimiento. Instituto de Ciencias del Mar, CSIC. https://digital.csic.es/bitstream/10261/145906/1/Morales_1987.pdf.

Nimesh, N., & Jain, S. (2018). Importance of otolith microchemistry as pollution indicator: A brief review. Journal of Environmental Biology, 32(2), 285–290.

Panella, G. (1971). Fish otoliths: Daily growth layers and periodical patterns. Science, 173(4002), 1124–1127. https://doi.org/10.1126/science.173.4002.1124.

Paradis, S., Magnan, P., & Audet, C. (2021). Fractal geometry in otoliths discriminates cryptic fish species. Marine Ecology Progress Series, 673, 1–15. https://doi.org/10.3354/meps13822.

Popper, A. N., & Fay, R. R. (2011). Rethinking sound detection by fishes. Hearing Research, 273(1–2), 25–36. https://doi.org/10.1016/j.heares.2009.12.023.

Ross, P. M., Scanes, E., Byrne, M., Ainsworth, T. D., Donelson, J. M., Foo, S. A., ... & Parker, L. M. (2023). Surviving the Anthropocene: The resilience of marine animals to climate change. In S. J. Hawkins, B. D. Russell, & T. P. A. (Eds.), Oceanography and marine biology (Vol. 61, pp. 35–80). CRC Press. https://doi.org/10.1201/9781003363873-3.

Rountrey, A. N., Coulson, P. G., Meeuwig, J. J., & Meekan, M. G. (2014). Water temperature and fish growth: Otoliths predict growth patterns of a marine fish in a changing climate. Global Change Biology, 20(8), 2450–2458. https://doi.org/10.1111/gcb.12617.

Sadighzadeh, Z., Valinassab, T., Vosugi, G., & Motallebi, A. A. (2022). Application of otolith shape analysis for stock discrimination of Johnius belangerii in the northern Persian Gulf. Environmental Biology of Fishes, 105(8), 1099–1111. https://doi.org/10.1007/s10641-022-01320-x.

Schultz, H., Jones, C. M., & Tracey, S. R. (2024). Advancing fish ecology through otolith analysis: A global synthesis of recent developments. Reviews in Fish Biology and Fisheries, 34(1), 123–145. https://doi.org/10.1007/s11160-024-09848-0.

Secor, D. H., Dean, J. M., & Laban, E. H. (1992). Otolith removal and preparation for microstructural examination. In D. K. Stevenson & S. E. Campana (Eds.), Otolith microstructure examination and analysis (pp. 19–57). Canadian Special Publication of Fisheries and Aquatic Sciences.

Sturrock, A. M., Trueman, C. N., Milton, J. A., Waring, C. P., Cooper, M. J., & Hunter, E. (2022). Physiological influences can outweigh environmental signals in otolith microchemistry research. Marine Ecology Progress Series, 644, 1–18. https://doi.org/10.3354/meps13363.

Tuset, V. M., Lombarte, A., & Assis, C. A. (2008). Otolith atlas for the western Mediterranean, north and central eastern Atlantic. Scientia Marina, 72(S1), 7–198. https://doi.org/10.3989/scimar.2008.72s17.

Wright, P. J., Panfili, J., Morales-Nin, B., & Geffen, A. J. (2002). Types of calcified structures: Otoliths. In Manual of fish sclerochronology (pp. 31–57). IRD Éditions. https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2022-03/010043026.pdf.