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Clues sought for decline in Hawaii humpback whale sightings

HONOLULU — Researchers are convening this week to compare clues about a significant decline in the number of sightings of North Pacific humpback whales in their traditional breeding grounds off Hawaii.

Fewer sightings doesn’t necessarily mean the iconic giants are dying off, or that they’re not still migrating to the islands. But the apparent disappearance of many whales from a historically predictable location is causing concern and some researchers believe there’s a link between warmer ocean temperatures in Alaska and the effect that has on the whales’ food chain.

While scientists say it’s too early to draw any conclusions about the phenomenon, the decline has sparked enough interest that a consortium of whale experts will meet today and Wednesday in Honolulu to compare data and attempt to better understand what’s happening and what to do about it. The drop in sightings is estimated at 50 percent to 80 percent over the past four years.

Researchers use a variety of monitoring methods to count the whales, including visual observations conducted aboard ships that follow specific coordinates and acoustic monitoring that listens for whale songs from fixed underwater locations. There is also a less scientifically rigorous count done each year where residents on shore report their sightings.

The humpbacks traditionally migrate each autumn from Alaska, where they feed during the summer months, to Hawaii, where they mate and give birth during the winter. Based on the latest large-scale population study, it is estimated that half of all North Pacific humpbacks make the journey to Hawaii each year, putting the total number of whales making the 6,000-mile round trip migration at around 11,000 annually.

Most humpbacks were taken off the Endangered Species list in 2016 but are still federally protected.

Officials with the National Oceanic and Atmospheric Administration hope this week’s meetings will help them to form a consensus about what to do going forward to help ensure the species’ continued success. NOAA conducts research, creates federal regulations and enforces laws meant to protect the whales and their habitats.

Marc Lammers, research coordinator for the agency’s Hawaiian Islands Humpback Whale National Marine Sanctuary, said different research groups have collected various data sets that all seem to point toward decreased whale sightings.

“People started to report fewer sightings and there was concern about what might be going on,” Lammers said in a telephone interview. “We’ve noticed that there’s been basically a decrease in the overall acoustic energy levels that we’re picking up produced by humpback whale songs.”
Source: Hawaii Tribune Herald

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