‘Gahirmatha dolphins migrated to deep sea due to climate change’

Migration of dolphins from Odisha’s Gahirmatha marine sanctuary to deep sea; climate change and unfavourable weather; illegal fishing practices — these were the reasons why aquatic mammals’ population saw a decline in the state — according to officials.

Down to Earth reported on 25 February, 2020, that only 62 dolphins were spotted at Gahirmatha — down from 126 in 2019. Their number was pegged at 307 in 2015.

Gahirmatha is located within Bhitarkanika National Park in Odisha’s Kendrapara district.

The state’s total dolphin count was pegged at 233, down from 259 in 2019, according to the new census report. Their total count in 2018 was 469.

“We conduct dolphin census only two kilometres from the coast, as a result of which it was not possible to count them deep in the sea. Few dolphins were spotted in Gahirmatha this year due to dense fog on the census day. Dolphins often migrate to other areas as well," said Muntaz Khan, researcher and zoology teacher at a government college in Bhawanipatana. 

"In 2015, we sighted a transient population of humpback dolphins at Gahirmatha. A total of 307 such dolphins were spotted in 2015,” he added.

 According to Lala Aswini Kumar Singh, a former wildlife researcher in the forest department of Odisha:

Reduction in the dolphin count could be due to their migration from Gahiramatha to Chilika lake and towards the deep sea. Climate change and bad weather could have also pushed them towards deep sea. Their death is an unlikely reason, as only a few carcasses have been found on the beach.

The decrease indicated a change in Gahirmatha’s ecosystem, according to Biswajit Mohanty, secretary, Wildlife Society of Odisha.

“There is something wrong with Gahirmatha’s ecosystem. Sometimes, dolphins are trapped in fish nets or hit by propellers of fishing trawlers. Marine sanctuary had been disturbed due to illegal fishing, despite the ban enforced to protect Olive Ridley sea turtles in Gahrimatha,” he said.

Meanwhile, according to the census report, Irrawaady dolphins saw a spurt in Chilika lake. The count of Irrawaddy dolphins increased to 146 from 130 in 2019. 

According to Sudhakar Kar, former wildlife researcher and herpetologist in Forest and Wildlife Department, Odisha:

Irrawaddy dolphins reside in estuaries of Chilika lake. Humpback dolphins live in sea water near the coast at Gahirmatha. Many Irrawaddy dolphins migrated to Chilika Lake from Gahrimatha this year. Erratic and untimely rain due to climate change reduced the saltiness of sea water, due to which humpback dolphins migrated into the deep sea as well. 

He said this was the reason forest officials did not spot any humpback dolphins at Gahirmatha this year.

“There was a time when dolphins were seen jumping out of the sea. But they are hardly seen these days,” said Ashok Behera, a fisherman.

In 2019, the Odisha High Court had ordered the state government to initiate the demolition of illegal prawn gherries in Chilika Lake to restore the wetland’s ecology.

Gherries are encroached areas used for illegal prawn cultivation inside wetland areas. Illegal prawn farming has choked Chilika’s biodiversity.

“Acting on the court’s order, we demolished around 162 square kilometers of illegal prawn gherries last year,” said Susant Nanda, chief executive of the Chilika Development Authority.

Officials conducted a dolphin census for the first time in Gahirmatha in 2015. The census in 2016 and 2017 had been cancelled due to bad weather. The 2020 census was the fourth such dolphin census undertaken in the marine sanctuary.

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