Is the Deccan Mahseer, Tor khudree (Sykes, 1839) (Pisces: Cyprinidae) fishery in the Western Ghats Hotspot sustainable? A participatory approach to stock assessment

Abstract

In this paper, we use a participatory approach, to assess the suitability of data provided by local fishers for determining the demography and harvest rates of endangered species, exploited in remotely located small-scale fisheries. We specifically focus on the Deccan Mahseer (Tor khudree) in the Western Ghats Hotspot of Peninsular India. Using catch data provided by local fishers, we assessed the dynamics of exploited populations of T. khudree from six major fishing sites having varying patterns of harvest (commercial vs. subsistence) and protection status (protected vs. non protected area). Based on annual length frequency data, growth parameters of T. khudree were worked out as L∞ = 383.25–1202.25 mm total length and K = 0.12–0.23 year−1. The length frequency data of T. khudree individuals exploited from two fishing sites indicated that a high share of the catches throughout the year, are contributed by immature size classes. The total mortality coefficient (Z) was calculated to be between 0.35 year−1 and 0.95 year−1 and the fishing mortality coefficient (F) between 0.13 year and 0.8 year. The fishing mortality rate of T. khudree in Poringal Reservoir (0.8 year) may probably be one of the highest for any species of Mahseer in India, and points to the targeted indiscriminate exploitation by local fishers. Exploitation rate (E) (0.34–0.84 year−1) was higher than the expected optimal level (0.5) at all, but one fishing sites revealing that T. khudree populations are overfished in the study region. Further, a comparison of the exploitation rate at various fishing sites revealed no significant differences between commercial and subsistence harvest, as well as inside and outside protected areas. In spite of its ‘endangered’ status, T. khudree receives no protection even in Biodiversity Hotspots like the Western Ghats, and its fishery is under threat of an imminent collapse. Management guidelines for sustainable Mahseer fishery in the region are suggested.