Bhubaneswar: The Chilika lake in Odisha has emerged as the single largest habitat of Irrawaddy dolphins in the world with the spotting of 155 such animals, a Chilika Development Authority (CDA) official said.

The finding is based on the preliminary report of the first ever 'Annual Monitoring' of the lake held on Saturday, CDA Chief Executive Susanta Nanda said.

The 'Annual Monitoring' was conducted by the CDA to count the number of the marine mammals and to study the hydrological impacts of removal of pen culture (locally known as gherries), he said yesterday.

The number is more compared to the last year's figure of around 100 dolphins during the annual census, Nanda said.

Stating that the results of the monitoring are being analysed by plotting the locational GPS, Nanda said the finer details were likely to take some time.

"The dolphins are now seen in different sectors of the lake where they were not seen before due to removal of obstruction for their migration," Nanda said.

While dolphins are seen in different parts of the lake has raised the hope of eco-tourism, Nanda said high degree of cautions was necessary to preserve them by taking up responsible tourism.

The monitoring also revealed that the lake houses around 0.9 million birds which is similar to the trend of population over the years. No new species is identified during the monitoring, he said.

However, it has been observed that the birds, mainly the migratory ducks, have started colonising new areas previously covered by pen culture as their new habitat, he said.

The CDA official said Barunakuda and Krushnaprasad offered tremendous opportunity for eco-tourism due to congregation of the winter birds along these new areas.

Some waders have already started leaving the lake, but other migratory birds have prolonged their stay mainly because of cool nights and increased available food in the lagoon, the preliminary report said.

The sea grass bed which was reduced to 86 square km in 2016 has now shown a marked improvement and with ground trothing stands at 135 sq km indicating improved hydrological condition of the lake, it said.

"This will provide ample opportunity for the mud crabs to grow. The presence of Sponge, which was found by the ZSI in the lake before 1985 and had disappeared thereafter, have made their appearance indicating a clean and healthy eco-system," the report said adding that Spongillaalba species was identified by the monitoring team in certain locations.

The use of zero nets for fishing has also been reduced significantly, but they still pose the maximum threats to the eco-system of the lake as they increase siltation.

All the three channels and the Palur canal are free from obstruction. But, the number of nets used in the outer channel for fishing is silting up the channel at a very fast pace, it said.

Nanda said this problem was needed to be discussed with the fishermen of these localities to prolong the life of the lagoon by promoting responsible fishery and adhering to certain self restrictions to reduce the siltation.