Implications for Habitat Suitability Using Length–Weight Relationships and Condition Factors in the Chirchik River, Syr Darya Basin

Abstract

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.