Ichthyofaunal diversity and ecological characteristics of upland Mehao and Ganga Lakes, Arunachal Pradesh

Arunachal Pradesh is blessed with vast and variety of aquatic resources manifested in the forms of streams, falls, rivers and lakes. Amongst several coldwater lakes of the state, Mehao Lake in lower Dibang valley district and Ganga lake in Papum Pare district are two such water bodies where hardly any work was undertaken in the context of limnological characteristics and fish production potential. The proposed work embodies to study the ecology, the status and sustainable utilization of biotic communities and the future prospect of sport and food fisheries in these lakes. The mean pH of Ganga Lake water ranged from 6.8–8.2 throughout the study period (2012–13). However, the Mehao Lake water is slightly acidic having pH 6.2–6.8. The aquatic life forms of both the lakes comprised of diversified groups of planktonic, periphytic, benthic and neustonic life forms. However, due to distinctness of the topographic locations as well as variability in physico-chemical parameters particularly temperature regimes of both the lakes created different micro distributional pattern both in diversity and abundances among those life forms. It is to mention that the Mehao Lake is devoid of any aquatic macrophytes. However, Ganga Lake contains dispersed population of macrophytes in different littoral areas particularly with introduced groups. The zooplankton population of Ganga Lake comprised of 6 genera of Cladocera, 4 genera of Copepod and 6 genera of Rotifera along with various other minor population of larval forms as well as Protozoans. The phytoplankton population of Ganga Lake comprised of Chlorophyceae with 17 genera, Cyanophyceae with 9 genera and Bacilarophyceae with 19 genera. The study on plankton population and diversity in the Mehao Lake revealed that there are quite diverse plankton population exists in the lake water. The study indicated the abundance of smaller sized wild fish with the dominant species as Danio aquepinatus, Danio devario, Puntius ticto and Rasbora daniconius in Ganga Lake. However, four species of fish viz. Salmo trutta fario, Cyprinuscarpio, Neolissochilus hexagonolepis and Exostoma labiatum have been identified from the Mehao Lake. It is evident from the two years of consecutive study that both Ganga and Mehao Lakes possess sufficiently congenial environment for undertaking fishery activities in terms of aquaculture and sports fisheries.