Saturday, January 02, 2010

Hawaii's false killer whales truly kama'aina

Mr. Big Island here. Just thinking, I haven't been snorkeling in a while. May be time to get back in the water and swim with the fishes. That leads me to our question this week. An anonymous writer asks, "Is a false killer whale a whale or a dolphin? Are they endangered?"

Pseudorca, or false killer whales, are a rare open-ocean dolphin. Mr. Big Island got a little help answering this question from his friends at the Cascadia Research Collective, a nonprofit research organization based in Olympia, Wash.

These false killer whales are at risk. They have the smallest population size of any toothed whale or dolphin in Hawaiian waters, they feed high on the food chain and have to compete with humans for food. They accumulate high levels of persistent organic pollutants such as PCBs and flame retardants. In Hawaiian waters, many are killed each year or seriously injured in the offshore longline fishery. Since 1999, so many have been killed its been impossible for the false killer whales to maintain a sustainable level. There is evidence the island-associated population has declined substantially during the last 20 years, and a petition to list them under the Endangered Species Act was recently submitted.

In Hawaiian waters, the false killer whales are found both near and off shore. More is known about Pseudorca in Hawaii than anywhere else in the world. The ones found around the main Hawaiian islands are genetically isolation from Pseudorca elsewhere.

The island-associated population is small, with only about 120-160 individuals, while there are an estimated 484 in the offshore population in Hawaii waters.

False killer whales look nothing like killer whales. Their genus, Pseudorca, comes from similarities in their skull and teeth. Pseudorca mature in their teens, and may live to be in their 60s. The females give birth to one calf every six or seven years. Like humans, the females go through menopause, and have a long post-reproductive period. They feed on large fish like yellowfin tuna, mahimahi, ono and swordfish.

A Task Reduction Team is soon to be formed by National Marine Fisheries Service to find ways to reduce the bycatch. In addition, potential impacts from toxins, deliberate shooting and reduced prey availability may impact Pseudorca in Hawaii.

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