Challenges in otolith shape analysis in riverine gobies: Effects of growth and asymmetry

Articles in Press

Document Type : Research Paper

Authors

1 NRF-South African Institute for Aquatic Biodiversity, Private Bag 1015, Makhanda 6140, South Africa

2 Ichthyology and Molecular Systematics Research Laboratory, Zoology Section, Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran

3 Department of Biology, Bo. C., Islamic Azad University, Borujerd, Iran

10.22124/cjes.2026.9874

Abstract

Otolith morphology has long been a valuable tool in fish taxonomy and, more recently, in stock assessment and the analysis of intraspecific population structure. However, it is influenced by a complex interplay of intrinsic and extrinsic factors, which can introduce variability and obscure meaningful patterns. This study investigated the effects of two such factors, ontogenetic development and left-right asymmetry, on otolith shape in two south Caspian riverine gobiid species, Ponticola gorlap and P. patimari, using single-population samples while controlling for other variables. Results showed strong, consistent ontogenetic effects: smaller individuals exhibited compact shapes, whereas larger individuals had more elongate outlines with pronounced regional features. Left-right asymmetry was also evident, with inconsistent directional trends suggesting developmental noise rather than functional adaptation. Wavelet-based classification accuracy was modest (overall classification: 32.2% and 40.9%, respectively), reflecting considerable morphological overlap among size classes and emphasizing the limitations of relying solely on otolith shape for population discrimination. These findings highlight the need to standardise for growth, analyse both otoliths when feasible, and integrate otolith data with complementary sources such as molecular information. Such an integrative approach is essential for accurately interpreting otolith shape variation and ensuring effective management of fish populations.

Keywords

Caspian Journal of Environmental Sciences

Articles in Press, Corrected Proof
Available Online from 26 August 2026

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