In this Jan. 23, 2005, file photo, a humpback whale leaps out of the water in the channel off the town of Lahaina on the island of Maui in Hawaii. (AP Photo/Reed Saxon, file)
File - In this Jan. 23, 2005, file photo, a whale leaps out of the water in what is called "breaching," as seen from a whale watching boat operated by the Pacific Whale Foundation in the channel off the town of Lahaina on the island of Maui. (AP Photo/Reed Saxon, File)
In this Oct. 3, 2009, file photo, boaters and fishermen watch as a group of up to six humpback whales feed on herring near Ketchikan, Alaska. (Tom Miller/Ketchikan Daily News via AP, file)
HONOLULU — Researchers are gathering to compare clues on the reasons behind a significant decline in the number of sightings of North Pacific humpback whales in their traditional breeding grounds in waters around Hawaii.