FISH DIVERSITY AND PRODUCTIVITY OF SELECTED RESERVOIRS OF SOUTHERN TAMIL NADU
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Date
2017-08-28
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
The present investigation was conducted to study hydro-biological parameters, zooplankton diversity, fish diversity and productivity in Manimuthar, Vaigai and Kullursandai reservoirs from December, 2014 to November, 2016. The water quality parameters were recorded for all three reservoirs and the water temperature ranged from 27.8±0.3 to 29.7±0.4 oC, transparency from 15.3±0.4 to 92.4±6.1 cm, total dissolved solids from 10.2±0.7 to 33.9±2.1 mg/l, pH from 7.1±0.1 to 7.7±0.1, dissolved oxygen from 5.8±0.1 to 6.7±0.2 mg/l, total alkalinity from 44.4±1.3 to 170.9±4.9 mg/l, total hardness from 28.9±0.9 to 66.6±1.9 mg/l, nitrate from 0.8±0.1 to 1.0±0.2 µg at NO3-N/l, phosphate from 0.2±0.0 to 0.8±0.1 µg at PO4-P/l and chlorophyll ‘a’ from 11.3±0.3 to 192.6±4.8 mg/m3. The average water quality during study period indicated that these three reservoirs were ideal for fisheries productivity. In present study, 29 species of zooplankton representing two phyla, four classes, five orders, eight families and 18 genera were recorded from these reservoirs. Zooplankton diversity indices were calculated for Margalef’s species richness (1.12 to 1.2), Pielou’s evenness (0.99 to 1) and Shannon-Wiener species diversity (2.31 to 2.32). The results indicated moderate zooplankton diversity in these reservoirs. The present investigation discovered presence of 66 species of fishes under eight orders, 19 families and 40 genera. The highest number of fishes were recorded in Manimuthar (62 species) followed by Vaigai (44 species) Kullursandai (15 species). The order with diverse species composition was Cypriniformes (33 species). Cyprinidae was the most diverse family with 32 species. Of the 66 fishes, 59 species were supporting capture fishery, 40 species could possibly support ornamental fishery and 18 species could be used for capture based culture fishery. The indigenous fishes Dawkinsia arulius, D. tambraparniei, D. rohani and Hypselobarbus curmuca are recorded as threatened and need conservation initiatives. The ranges of fish diversity indices calculated during study period were Shannon-Wiener species diversity (3.67 to 5.58), Margalef’s species richness (3.2 to 11.06), Pielou’s evenness (0.94 to 0.96), Average taxonomic distinctness (84.43 to 86.38) and Total phylogenetic diversity (782.4 to 3,100). The calculated ranges of fish diversity indices indicated healthy nature of ecosystem with rich species diversity in descending order from Manimuthar > Vaigai > Kullursandai. The results of trophic state index (TSI) indicated that the Manimuthar as mesotrophic reservoir, Vaigai as eutrophic and Kullursandai as mid-eutrophic. The highest value of the morpho-edaphic index (MEI) was recorded in Kullursandai (11.93±0.72/year) followed by Vaigai (3.57±0.10/year) and Manimuthar (0.61±0.04/year). The potential fish yield was predicted for Manimuthar as 2.74±0.08 kg/ha/year, Vaigai as 6.29±0.08 kg/ha/year and Kullursandai as 10.96±0.33 kg/ha/year. The average potential fish yield was 10.76 kg/ha/year in Manimuthar, 47.18 kg/ha/year in Vaigai and 440.75 kg/ha/year in Kullursandai. The mean value of the fish production during the last ten years from Manimuthar was 8,646 kg/year, Vaigai was 29,557.10 kg/year and Kullursandai was 48,534 kg/year. The catch per unit effort (CPUE) observed during study period was 10 kg/coracle/day in Manimuthar, 4 kg/coracle/day in Vaigai and 122 kg/coracle/day in Kullursandai. The Cytochrome C Oxidase subunit I gene (COI) sequence of Anguilla bengalensis (Gray, 1831) and Xenentodon cancila (Hamilton, 1822) were generated. Considering all the hydro-biological parameters, zooplankton and fish diversity, TSI, MEI, predicted potential fish yield and CPUE of studied reservoirs reflected Kullursandai as the most productive reservoir followed by Vaigai and Manimuthar. To enhance the fish yield, the stocking of 40 to 150 mm sized fingerlings at the rate of 1000 fingerlings/ha in Vaigai reservoir and 2000 fingerlings/ha in Kullursandai and Manimuthar reservoirs are recommended Optimizing the use of available water area through the cage or pen culture practices is essential to augment fish yield in Vaigai and Manimuthar reservoirs.
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