Ms Smith: Now we are heading towards the shark lagoon in the Central Aquarium.
Nam: Can we also see blue whales and dolphins?
Ms Smith: I'm afraid you can't. These animals shouldn't be kept in captivity. It's also impossible to build a suitable habitat for the blue whale.
Mai: The blue whale is the largest animal on Earth, isn't it?
Ms Smith: That's right. It can weigh as much as 30 elephants. It's longer than the longest jumbo jet.
Nam: Wow! Amazing! But are these animals an endangered species?
Ms Smith: Yes, they're classified as endangered on the IUCN Red List. Before the 1920s they were considered too difficult to hunt because of their size and speed. However, technological advancement gave rise to the hunting and killing of whales. It became a profitable business, and more than 340,000 blue whales were killed in the first half of the 20th century.
Mai: So how many blue whales are left now?
Ms Smith: Scientists estimate that the current population is between 10,000 and 25,000 individuals.
Mai: Do they face other threats?
Ms Smith: Unfortunately, large cargo or cruise ships also pose a threat to blue whales, which get hit by these huge boats especially at night when they feed near the water surface.
Nam: That's very sad! How about pollution? Has it affected the blue whale?
Ms Smith: Yes, it has. Our oceans are filling up with plastic so blue whales could be swallowing 10 million pieces of plastic every day. Another threat is climate change. Rising temperatures are causing a decline in their food sources.
Nam: So what can we do to protect them? ...