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Length–weight relations (LWR) were estimated for 14 endemic and indigenous fish species from the Aral Sea basin: Alburnoides holciki Coad et Bogutskaya, 2012; Capoetobrama kuschakewitschi (Kessler, 1872); Cottus spinulosus Kessler, 1872; Glyptosternon oschanini (Herzenstein, 1889); Gobio lepidolaemus Kessler, 1872; Gobio nigrescens (Keyserling, 1861); Iskandaria kuschakewitschi (Herzenstein, 1890); Iskandaria pardalis (Turdakov, 1941); Paracobitis longicauda (Kessler, 1872); Sabanejewia aralensis (Kessler, 1877); Schizothorax fedtschenkoi Kessler, 1872; Triplophysa daryoae Sheraliev, Kayumova et Peng, 2022; Triplophysa ferganaensis Sheraliev et Peng, 2021; and Triplophysa uranoscopus (Kessler, 1872). Measurements were taken for total length (0.1 cm precision) and total weight (0.1 g precision). The LWR parameters were determined using a linear logarithmic regression model of weight against length in which values for the slope of the regression, b , that are higher and lower than 3 indicate positive and negative allometric growth, respectively. The estimated values of parameter b ranged from 2.703 ( Iskandaria kuschakewitschi ) to 3.162 ( Gobio nigrescens ). The correlation coefficient ( r 2 ) values varied from 0.951 to 0.993, indicating a strong positive relation between length and weight. The maximum total lengths of four of the species ( Glyptosternon oschanini , Iskandaria kuschakewitschi , Triplophysa daryoae , and Triplophysa uranoscopus ) constitute new records, and the LWRs of twelve fish species have hitherto not been available in FishBase.

Snow trout ( Schizothorax ), endemic to the high-altitude freshwater systems of the Tibetan Plateau and the Tien Shan Mountains region, are key components of these ecosystems. This fish lineage may serve as an appropriate model to understand the evolution of biodiversity in the Tien Shan Mountain water ecosystems. However, research has been hindered by poorly understood phylogenetic relationships, unresolved taxonomic classifications, and ambiguous biogeographical histories, particularly in the underexplored western regions of the Tien Shan Mountains. Here, we analyzed three mitochondrial genomes assembled using the next-generation sequencing data of three snow trout species, S. eurystomus , S. fedtschenkoi , and Schizothorax sp., from the western Tien Shan Mountains. These genomes range from 16,584 to 16,592 bp in length and include 13 protein-coding genes (PCGs), 2 rRNAs, 22 tRNAs, and a control region. Our phylogenetic analyses suggest six snow trout from the Tien Shan Mountains region were divided into two distinct clades: clade I comprises S. fedtschenkoi , and Schizothorax sp., and clade II includes S. eurystomus , S. biddulphi , S. pseudoaksaiensis , and S. argentatus . We classified Schizothorax sp. as a valid independent species based on comprehensive phylogenetic trees and DNA barcode genetic distance. The dramatic uplift of the Tien Shan Mountains during the Late Miocene to the Pliocene, followed by periods of isolation on its eastern and western flanks, has driven extensive speciation, contributing to the rich diversity observed today. Notably, S. eurystomus spread westward along the Pamir-Tien Shan corridor, shaping the region’s current biogeographical distribution of snow trout species. Our findings not only clarify the evolutionary histories of snow trout in the Tien Shan Mountains but also advance our understanding of the mechanisms shaping the rich biodiversity.

Accurate fish growth and condition assessment is central to understanding the ecological health of freshwater ecosystems. Despite severe anthropogenic pressures, ecological and biometric studies of fish populations from heterogeneous habitats of the Chirchik River, a key tributary of the Syr Darya, remain poorly studied. Here, we demonstrate the length–weight relationships (LWRs) and condition factors of five freshwater fish species from the upper and middle parts of the Chirchik River, including two native and three invasive species. Observed positive ( Gymnodiptychus dybowskii , Rhodeus ocellatus , and Micropercops cinctus ) and isometric growth ( Pseudorasbora parva and Cottus jaxartensis ) patterns indicate good habitat and resource conditions in both reaches of the river. Relative condition factor ( K n ) values were consistently near 1.0 and did not differ significantly among species, indicating a stable physiological status. In contrast, Fulton’s condition factor ( K ) varied significantly, reflecting marked interspecific differences in body robustness and energy allocation strategies. Taken together, our findings provide vital biometric data for poorly studied and heavily human‐impacted rivers of Central Asia, and demonstrate the utility of combined growth and condition metrics as indicators of environmental suitability.