The Western Ghats of India harbours an exceptional diversity of endemic freshwater fishes, which are threatened because of various anthropogenic stressors, including biological resource use. Lack of organized studies on the population dynamics and exploitation levels of endemic species, however, has hindered the development and implementation of systematic conservation action plans in this region. This is especially true for large cyprinid fishes threatened because of overharvest. This study examined length–weight relationships and length‐structured population dynamics of an endemic large cyprinid (Hypselobarbus kurali), based on data obtained from an artisanal gill‐net fishery in Malampuzha Reservoir. Length–weight analysis suggested the fish exhibited significantly lower exponents than expected under isometry, indicating the growth of H. kurali in the reservoir was negative allometric. The von Bertalanffy growth formula fitted to the length‐frequency data indicated H. kurali grew relatively slower than other large cyprinids in this region. Statistical analysis of recruitment revealed two peaks, implying the fish have two spawning bouts each year. Analysis of mortality and exploitation of the species revealed large‐sized individuals were targeted by the fishers, resulting in an exponential decline in the survivors in the virtual population analysis. Relative yield‐per‐recruit and relative biomass‐per‐recruit analysis indicated the current exploitation rate for the population was greater than the exploitation rate under which the stock would be reduced to half its unexploited biomass. Further, the current exploitation level was more than 60% of the expected maximum exploitation above which the population could collapse. The results of this study identify a serious need to develop and implement management plans to guide the future sustainability of the reservoir fishery of H. kurali.

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This study presents fundamental information on the reproductive biology of Puntius denisonii, an endemic and threatened aquarium fish of the Western Ghats Hotspot. Results are based on the observations from three river systems, Chandragiri, Valapattannam and Chaliyar. Maximum observed total length in P. denisonii was 162mm and 132mm for males and females, respectively. Males attained sexual maturity at a lower size than females with mean size at first maturity determined as 85.33±1.52 mm for males and 95.66±1.15 mm for females. Puntius denisonii spawned from October to March with minor differences in the peak breeding months between the three river systems, which were studied. Sex ratio deviated significantly from 1:1 and was skewed in favour of males. Absolute fecundity varied from 376 (fish of 102mm total length) to 1098 (fish of 106mm total length) eggs. Currently, the closed seasons for P. denisonii have been put in place during June, July and October based on the (mis)assumption that the species breeds during these three months. However, the results of the present study have helped us to understand more about the reproductive biology of the species so as to recommend more appropriate seasonal closures. The months from October until March need to be designated as a closed season for protecting the breeding population of P. denisonii.