Otolith microchemistry reveals spatial population structure of Paracapoeta trutta in the Euphrates River Basin, Türkiye

In this study, the concentrations of 44 Ca, 88 Sr, 23 Na, 39 K, and 24 Mg were analyzed in lapillus otoliths of Paracapoeta trutta (Heckel, 1843) collected from Keban, Karakaya, and Atatürk Dam Lakes in the Euphrates River Basin between October 2023 and March 2024. Right and left otoliths were analyzed together for elemental composition. Otolith microchemistry indicated significant differences among populations inhabiting the three dam lakes. Across all populations, the elemental concentrations followed a consistent pattern of Ca > Sr > Na > K > Mg, with Ca identified as the dominant element. Element/Ca ratios also differed among reservoir populations, although the magnitude and significance of these differences varied among elements. Multivariate analyses, including principal component analysis (PCA), permutational multivariate analysis of variance (PERMANOVA), and quadratic discriminant analysis (QDA), revealed significant spatial differentiation among the three reservoir populations. QDA, evaluated using leave-one-out cross-validation (LOOCV), achieved an overall classification accuracy of 81.8%, with correct classification rates of 90.8, 88.7, and 66.2% for the Keban, Karakaya, and Atatürk Dam Lake populations, respectively. These findings indicate that otolith elemental signatures may serve as useful natural markers for discriminating the spatial population structure of Paracapoeta trutta in the Euphrates River Basin.