How important are herring to humpback whales? The role of herring in meeting the energetic requirements of humpback whales in a British Columbian feeding ground

Abstract

Management of cetacean populations is a global conservation concern. The North Pacific humpback whale (Megaptera novaeangliae) in Canada is listed as threatened under the Species At Risk Act, and prey reduction has been identified as a threat to this population. I used focal follows of humpback whales and underwater video of herring schools to estimate Pacific herring (Clupea pallasi) consumption by humpback whales in eastern Queen Charlotte Strait, British Columbia. I combined these results with a bioenergetic model to estimate sex- and age-specific annual energetic requirements of humpback whales to determine the proportion of these requirements that are met by herring. Non-reproductive female, pregnant female, and juvenile and adult male humpbacks met over 50% of their estimated energetic requirements by feeding on herring, while juvenile and lactating females met between 25 and 50% of their requirements. These results can lead to improved management decisions for both humpback whales and herring.