Hooghly estuary, the lowermost part of River Ganges in India, following the construction of Farakka barrage in 1975, witnessed improved freshwater inflow in the estuarine stretch of the river with significant impact on the salinity... more
Hooghly estuary, the lowermost part of River Ganges in India, following the construction of Farakka barrage in 1975, witnessed improved freshwater inflow in the estuarine stretch of the river with significant impact on the salinity regime, water transparency, suspended sediments and nutrient load leading to alternations in the distribution and abundance of fish and other biotic organisms like plankton and benthos. A detailed seasonal study was conducted in Hooghly estuary during 2010–2012 to evaluate the spatio-temporal changes in selected physico-chemical parameters like temperature, transparency, pH, free CO2, dissolved oxygen, specific conductivity, total alkalinity, total hardness, salinity, available nutrients
like nitrate, phosphate and silicate under the present hydrological regime in determining the distribution
of fish and other aquatic organisms. The salinity based zonation during pre-Farakka period apparently stands modified with a downward shift of freshwater zone. Accordingly, distribution and abundance of biotic communities like plankton and fish now present a completely different scenario from the past.
like nitrate, phosphate and silicate under the present hydrological regime in determining the distribution
of fish and other aquatic organisms. The salinity based zonation during pre-Farakka period apparently stands modified with a downward shift of freshwater zone. Accordingly, distribution and abundance of biotic communities like plankton and fish now present a completely different scenario from the past.
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The tidal freshwater areas of estuaries have received little attention in ecological research although they are often heavily stressed by environmental impacts. These critical habitats contribute significantly to the biodiversity of the... more
The tidal freshwater areas of estuaries have received little attention in ecological research although they are often heavily stressed by environmental impacts. These critical habitats contribute significantly to the biodiversity of the entire estuarine system. The present study aims to describe the fish diversity, assemblage structure and seasonal dynamics through data collected by intensive sampling of the tidal freshwater stretch of the Hooghly estuary (June 2010 to June 2012), the largest estuary in India formed in the Gangetic delta. The tidal freshwater zone of Hooghly has gained importance due to ecological changes during the post-Farakka period since this zone covers 74% of the total estuarine stretch. During the study, a total of 155 fish species belonging to 49 families and 15 orders were recorded from the tidal freshwater zone of the Hooghly estuary. The exotic ornamental fish Barbonymus altus (Tinfoil Barb) has been recorded from the tidal freshwater zone which is the first record of these species in Indian inland waters. A detailed analysis of the fish diversity revealed that of the total 155 species recorded from the study, 19 species have been listed in category of threatened fishes by National Bureau of Fish Genetic Resources (Lakra et al.,2010). This includes 16 vulnerable (VU) species and 4 endangered (EN) species. This signifies the role of tidal freshwater zone as an essential fish habitat due to its rich fish diversity and as a sheltered area which favours the growth and survival of larval and juvenile fish assemblages.
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The study deals with the diversity and spatial distribution of the dinoflagellate class Dinophyceae in Chilika lagoon, north east coast of India. Thirty-eight species of dinoflagellates belonging to eight families were recorded, of which... more
The study deals with the diversity and spatial distribution of the dinoflagellate class Dinophyceae in Chilika lagoon, north east coast of India. Thirty-eight species of dinoflagellates belonging to eight families were recorded, of which twelve are new reports to the lagoon. Of the twenty-six species recorded earlier, Neoceratium furca, Neoceratium fusus, Dinophysis caudata and Noctiluca scintillans were common among most of the earlier studies. Current study recorded presence of Dinophysis miles, which has not been encountered ever since it was first reported from the lagoon six decades ago. An updated checklist of dinoflagellates indicated presence of 68 species in the lagoon. The outer channel of the lagoon differed from southern and central sectors in distribution of dinoflagellates under the influence of salinity regime.