Densest whale population observed

Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 03 May 2011

Scientists doing observations in the Wilhelmina Bay in the western Antarctic have found an estimated two million tons of krill, and more than 300 humpback whales feeding on them. It is the densest population of these whales ever recorded, more than 15 per square mile.

Virtually all the larger animals of the Antarctic are either directly or indirectly dependent on krill.

The observations were made in May 2009, autumn in the southern hemisphere, and for four weeks, the scientists documented the gigantic assemblage of shrimplike krill and the ways whales fed on them. The researchers tagged 11 whales in Wilhelmina and nearby Andvord Bay, and found they rested during the day, dived to more than 300 yards in the late afternoon, and fed intensively at night as the krill moved toward the surface.

A humpback can consume half a ton of krill a day, but even at that rate, the authors estimate that the daily intake of the 306 whales was less than seven one-thousandths of 1 percent of the available krill.

Still, according to the lead author, Douglas P. Nowacek, an associate professor of marine conservation technology at Duke, the future of whales and krill in the Antarctic remains in doubt.

“Whales are going to have a few bumper years,” he said, because krill have less ice to hide under, leaving them exposed to predators for longer periods. But krill, feed and reproduce under the ice, and with warmer weather and more open water in winter, the population of krill is likely to decline.

“In the long term, krill aren’t getting the protection they need to reproduce effectively,” Dr. Nowacek said, “and if the krill disappear, the whales will, too.”

By: Nicholas Bakalar
Source: NY Times

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