GS PAPER I PRELIMS: General issues on Environmental ecology, Bio-diversity & climate change – that do not require subject specialization.

Context: The population of dolphins in Chilika, India’s largest brackish water lake, and along the Odisha coast has doubled this year compared with last year.

More about news:

• The population estimation exercise for dolphins and other cetacean species covered almost the entire coast of Odisha.
• Three species were recorded during the census, with 544 Irrawaddy, bottle-nose and humpback dolphins sighted this year, compared with 233 last year.
• Wildlife activists are elated over the sizeable growth in the population of endangered Irrawaddy dolphins, which are mostly found in Chilika lake, jumping from 146 in 2020 to 162 this year.
• Apart from Chilika, 39 Irrawaddy dolphins were sighted in the Rajnagar mangrove division, though their number has come down from 60 in 2020.
• The highest growth has been noticed in the case of humpback dolphins. Only two humpbacks were sighted in the Rajnagar mangrove in 2020. In 2021, however, this population grew astronomically to 281.
• The number of bottle-nose dolphins grew from 23 in 2020 to 54 this year.

The rise in the Irrawaddy [dolphin] population in Chilika can be attributed to

• eviction of illegal fish enclosures
• thousands of hectares of Chilika water were made encroachment-free
• Irrawaddy dolphins found unobstructed area for movement due to the COVID-19 lockdown

The Irrawaddy dolphin (Orcaella brevirostris)

It is a euryhaline species of oceanic dolphin found in discontinuous subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia

• • Although it is called the Irrawaddy river dolphin, it is not a true river dolphin, but an oceanic dolphin that lives in brackish water near coasts, river mouths, and estuaries.
  • The Chilika Lake in Odisha has emerged as the “single largest habitat of Irrawaddy dolphins in the world”, following a fresh monitoring survey that pegs the number of individuals of the endangered species at 155.
  • Irrawaddy dolphins are classified as ‘Endangered’ in the IUCN Red List of Threatened Species.

  Humpback dolphins

  • These dolphins are characterized by the conspicuous humps and elongated dorsal fins found on the backs of adults of the species.
  • They are found close to shore along the coast of West Africa and right along the coast of the Indian Ocean from South Africa to Australia.
  • The Indian Ocean humpback dolphin was only recogised in recent years is already classified as endangered.

Bottle-nose dolphins

• Bottlenose dolphins inhabit warm and temperate seas worldwide, being found everywhere except for the Arctic and Antarctic Circle regions.
• Bottlenose dolphins have the third largest encephalization levels of any mammal on Earth (humans have the largest), sharing close ratios with those of humans and other great apes, which more than likely contributes to their high intelligence and emotional intelligence.
• Common bottlenose dolphins are considered Least Concern by the IUCN on a global level.

https://www.thehindu.com/sci-tech/energy-and-environment/dolphin-boom-in-odishas-chilika-lake/article34292274.ece?homepage=true

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