Phenotypic Variability and Adaptive Differentiation of Tench (Tinca tinca L.) from Aquaculture and Natural Populations in Southern Kazakhstan

This study provides a comparative analysis of phenotypic variability in the morphological traits of tench (Tinca tinca L.) reared under aquaculture conditions and those from a natural population in southern Kazakhstan. The aim of the study was to evaluate phenotypic plasticity and adaptive differentiation between populations shaped by contrasting ecological and trophic environments. Morphometric analysis revealed significant differences in indices associated with growth patterns and body shape. The aquaculture group demonstrated faster somatic growth and lower variability, whereas the wild population exhibited greater morphological diversity, likely reflecting the effects of natural selection and habitat heterogeneity. The results indicate pronounced phenotypic divergence between pond-reared and wild tench, which is likely driven by environmental conditions and aquaculture practices. These findings highlight the high adaptive plasticity of the species and support its potential for domestication and large-scale aquaculture in Kazakhstan. Overall, the data may contribute to the development of conservation and restocking programs for natural populations, as well as to selective breeding strategies and sustainable aquaculture practices.