Population dynamics and conservation challenges of Diptychus maculatus Steindachner, 1866 in the Indus tributary of the Ladakh Trans-Himalayan region, India

The lack of demographic data for many endemic cold-water fishes limits effective conservation planning in the Trans-Himalayan region. This study presents the first comprehensive assessment of the population dynamics and exploitation status of the monotypic cyprinid Diptychus maculatus Steindachner, 1866, which inhabits the Indus tributaries of Ladakh, India. Three hundred specimens were analysed for length–weight relationships, growth parameters, and mortality. The species exhibited negative allometric growth (b = 2.89) and a mean condition factor of K (0.91), moderate physiological condition. von Bertalanffy growth parameters (L∞ = 407.40 mm; K = 0.11 yr–1; ϕ′ = 4.26) characterize D. maculatus as a slow-growing species, typical of high-altitude schizothoracines. Mortality analysis revealed total, natural, and fishing mortality rates of 0.48, 0.14, and 0.34 yr–1, respectively, with an exploitation rate of 0.71, indicating unsustainable exploitation levels. These findings suggest that D. maculatus populations in the Indus River tributaries of Kargil, Ladakh, are adversely affected by external pressures like sand mining, infrastructure development, and damming and face a decline, necessitating effective conservation and restoration strategies.