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False Killer Whale Populations Dropping Off In Hawaii

April 3, 2009

A new study shows that the population of false killer whales in waters close to Hawaii seems to have declined significantly over the past 20 years, the Associated Press reported.

The report said that the dolphin species are likely dropping due to the declining food supplies and their tendency to get caught and injured on the longline fishing lines from commercial fishing vessels that can span 50 miles.

Environmental activists recently sued the federal government for allegedly failing to prevent longline fishing fleets from accidentally capturing the animals off Hawaii.

False killer whales, which look like real killer whales except they’re almost completely black, can grow as long as 16 feet and weigh over one ton.

They inhabit tropical and temperate waters around the world, including Maryland, Japan, Australia and Scotland.

An estimated 120 false killer whales currently live in waters up to 60 miles off Hawaii’s coasts, according to Robin Baird, one of the study’s co-authors.

In 1989, aerial surveys of waters up to 34 miles offshore counted 470 individuals in one group of false killer whales, as well as groups of 380 and 460 individuals.

However, in the same area in 2000 and 2003, researchers saw no false killer whales during aerial surveys.

“Several surveys analyzed for the paper don’t say much about the false killer whale population when viewed individually,” said Baird, a marine biologist with Cascadia Research Collective in Olympia, Wash.

But he said when taken together the data makes a convincing case, adding that it presented a much more alarming picture.

He suspects a combination of longline fishing, declining prey, and environmental toxins are hurting the dolphins.

Both human and false killer whales eat yellowfin tuna, mahimahi, and ono, which can result in many of the whales getting caught up in longlines.

Heavy fishing by humans has depleted stocks of yellowfin tuna and other fish the dolphins consume, including mongchong, albacore tuna and swordfish.

The full study appears in this month’s edition of Pacific Science.

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