Description

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Context:

Sea otters are devouring thousands of green crabs — an invasive species native to Europe — at the Elkhorn Slough National Estuarine Research Reserve in California.

About Sea otters

Sea otters were heavily hunted in the 18th and 19th centuries for their thick, fine fur. In 1913, it was declared a fully protected mammal in California, but populations faced problems due to oil spills and habitat loss.
Their numbers increased again after they were listed as endangered and federally protected in 1977.

Contributing to the reduction of green crabs

Sea otters consume between 50,000 and 120,000 green crabs annually, effectively controlling their population. This represents a significant solution to the problem of invasive species on the West Coast of the United States.

Unique adaptations: Unlike other marine mammals, sea otters rely on a high metabolism rather than fat to stay warm in cold oceans. They consume about 25% of their body weight per day, making them voracious predators.

About Green Crab (Portunus Sanguinolentus)

The green crab is a common shore crab, known worldwide as the shore crab or green shore crab in the British Isles. It is among the top 100 "World's Worst Alien Invasive Species", showing off its invasive nature.
Habitat: Native to the Atlantic Ocean and the Baltic Sea, but has now spread to Australia, South America, and South Africa.

Physical Properties

In adulthood, the width of the carapace measures about 90 mm.
Coloration varies between green, brown, gray, and red, with delayed molting causing red coloration.
- - Red crabs are more aggressive compared to others.
Food: Feeds on small crustaceans, mollusks and worms.
Impact on Ecosystems: The invasive behavior of the green crab damages coastal ecosystems by:
Damage to seagrass beds, critical habitats for various marine species.
- - Overhunting of prey species is critical to the survival of other native species.
  - Competition with native species for resources such as food and habitat.

READ ABOUT

Sea otter | IUCN Status

Eurasian Otter

Source:

Indian Express

PRACTICE QUESTION

Q.Consider the following statements regarding sea otters:

Sea otters are primarily found along the coasts of the Pacific Ocean, particularly in the northern and central parts of the Pacific.
Sea otters play a crucial role in maintaining the health of kelp forest ecosystems by preying on herbivores that graze on kelp.
The conservation status of sea otters is classified as 'Least Concern' by the International Union for Conservation of Nature (IUCN).

Which of the statements given above is/are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(d) 1, 2, and 3

Answer: a

Explanation:

Statement 1 is correct: Sea otters are primarily found along the coasts of the Pacific Ocean, especially in the northern and central parts, including areas along the coastlines of Alaska, California, and parts of Russia.

Statement 2 is correct: Sea otters play a crucial role in maintaining the health of kelp forest ecosystems. They help regulate populations of herbivores such as sea urchins, which, if left unchecked, can overgraze on kelp, leading to the destruction of these important ecosystems.

Statement 3 is incorrect: The conservation status of sea otters is not classified as 'Least Concern.' They are listed as 'Endangered' or 'Threatened' depending on the region, particularly due to hunting, habitat loss, and oil spills, which significantly impact their populations.