Otolith Morphology and Population Discrimination of Triplophysa yarkandensis

To study the classification, identification, and discrimination between different geographical populations of Triplophysa yarkandensis and explore the related otolith morphology and fish life history, this study statistically analyzed the morphological otolith indices and fish bodies of 734 T. yarkandensis from the Yarkand River, Hotan River, and Tarim River using otolith morphology and fish ecology methods. The results showed that otoliths were small in T. yarkandensis, approximately elliptic, thicker in the middle, gradually thinning to the outer edge, and with a prominent protrusion in the center of the external surface. Otolith length was obviously larger than otolith width while the excisural notch was not obvious, wherein the rostrum was developed, the ventral otolith edge was smooth with a shallow arc, and the otolith dorsal had a crest-like ridge. No significant difference between left and right lapillus morphology was observed (P > 0.05). The otolith morphological indices followed a logarithmic function with the body length and weight (R2=0.48~0.62). It reflects the ontogenetic adaptation to the environment, and migration behavior mainly affects the relationship between otolith morphology and fish body morphology. The SHAPE software was used to extract the outer otolith contour of T. yarkandensis, revealing morphological differences between T. yarkandensis populations. The parameter with the largest discriminant coefficient, i.e., the one in which the morphological difference has the greatest significant effect, was screened. Therewith, the discriminant formula was set up to calculate the discriminant accuracy. Discriminant analysis between groups using fish morphology, otolith morphometry and elliptical Fourier analysis, respectively. The discriminant accuracy of the Hotan River and Tarim River populations was 96.0%, 61.4%, and 82.2%; the Yarkand River and Hotan River was 93.0%, 79.5%, and 87.9%; the Yarkand River and Tarim River populations was 96.5%, 77.5%, and 86.8%. Environmental factors such as water temperature, spatial niche adaptation, and habitat depth were the main causes of the otolith morphological changes, also affecting the behavior characteristics of typical T. yarkandensis life history, especially fish migration. In this study, the T. yarkandensis was found to live in high altitude, low habitat temperature, and high salinity and alkaline waters, so the fish body growth and the elements deposition rate onto otoliths were low. T. ya