VOA慢速英語：專家們齊聚為解夏威夷附近座頭鯨數量減少的原因

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Every winter, thousands of humpback whales migrate from Alaska to the warmer waters near the Hawaiian Islands. There, they have sex and give birth before making their return trip north.

From December to April, visitors from around the world travel to Hawaii. They go to watch the huge animals in the wild, as they break through the surface of the ocean and rise high into the air.

But since 2014, there has been a reduction in humpback whale sightings in Hawaii. Scientists say the decrease may suggest changes to the food supply.

American and international researchers, wildlife experts and federal officials are meeting in Honolulu this week to discuss the drop in humpback sightings.

Data presented at the meetings show a strong connection between warming oceans and the missing whales, said Christine Gabriele. She is a federal wildlife biologist who studies humpbacks at Glacier Bay National Park in Alaska.

Three conditions have warmed the ocean in Alaska since 2014, scientists say. There was a change in an ocean current, a warm “El Nino” period in 2016, and a huge “blob” of warm water in the area.

The current, called the Pacific Decadal Oscillation, changes from cool to warm over a period of many years. It changed to warm in 2014.

Gabriele said data shows that “it was more favorable for the whales when we were in a cold period, and then less favorable when the (current) switches to warm.”

Scientists have estimated about 11,000 North Pacific humpbacks migrate to Hawaii and back each year. That is about half of the total North Pacific humpback population. The trip is more than 9,500 kilometers.

The whales may be spreading out or moving north to cooler waters to find their prey -- the animals they eat for food. This could explain why there have been fewer sightings in Hawaii itself.

If the whales are forced to find new areas to feed, they could also be finding new areas to reproduce. Scientists say the whales could be going to waters in the Northwestern Hawaiian Islands. No people live on those islands. The area’s waters are not as closely observed as waters off the main Hawaiian islands.

Researchers say there have been decreases in sightings on some Hawaiian islands in the past. But those decreases were met with increased sightings in other parts of Hawaii.

But in the last four years, there has been a reduction of between 50 and 80 percent across all of the main Hawaiian islands. Gabriele calls this “unprecedented,” or never seen before.

Officials with NOAA, the National Oceanic and Atmospheric Administration, hope this week’s meetings will help them form a plan and get money necessary to help the species. NOAA does research, creates federal rules and enforces laws meant to protect the whales.

Marc Lammers is with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary. He said, “At least in Alaska, there’s something happening with the prey.” He added that scientists have not been able to determine whether the issue is only in Alaska or across a greater North Pacific area.

Lammers said, “There is no question that the world is changing, the oceans are changing.” He said the humpback whales are “reflecting” that change.

I’m Caty Weaver.

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Words in This Story

migrate - v. to move from one area to another at different times of the year

El Nino - n. a flow of unusually warm water along the western coast of South America that causes many changes in weather in other places (such as a lot of rain in areas that are usually dry)

blob - n. something that does not have a regular shape

determine - v.? to learn or find out (something) by getting information?

switch - v. make a change from one thing to another

reflect - v. to show (something): to make (something) known