Deaths and Entanglements of Humpback Whales, Megaptera novaeangliae, in the Main Hawaiian Islands, 1972-1996

Abstract

Reports of humpback whales, Megaptera novaeangliae, that either died or were entangled in Hawaiian waters from 1972 through October 1996 were analyzed to determine age class (estimated from body length and/or notes), location, annual frequency, and seasonal distribution of occurrence. Using reports collected from the National Marine Fisheries Service Pacific Area Office and published news reports, 26 whales were identified and their records analyzed. Deaths and entanglements were predominantly of calves of the year. Greatest incidence of deaths and entanglements occurred off the islands of Hawai'i, Maui, and O'ahu during the month of February. Of the 26 reported cases, 19 animals were confirmed dead. In the majority of the cases cause of death was unknown. However, shark attacks appear to be a secondary cause of death subsequent to entanglement, perinatal death, calf abandonment, illness, or unknown causes. The annual frequency of occurrence over the 25-yr period indicates an increasing trend of entanglement in natural fiber and synthetic lines since 1992 and a three-fold increase in death and entanglement occurrences related to human activity in 1996.