Historic catches and opportunistic sightings of humpback whales
(Megaptera novaeangliae)
in the Hauraki Gulf, New Zealand
Authors:
Laura Torre-Williams
Emmanuelle Martinez
Karen A Stockin
Abstract:
Humpback whales were once abundant in New Zealand (NZ) waters but are now infrequently sighted. Most available whaling data on this species were recorded at Tory Channel station, Cook Strait, during the northern migration. In contrast, little has been reported from catches at the Whangaparapara station, Great Barrier Island, Hauraki Gulf, North Island. Furthermore, there is a paucity of data on reported catches of humpbacks harvested during the southern migration. We examined two data sets: Historical, reported, records from Whangaparapara station; and contemporary opportunistic sightings from the Hauraki Gulf compiled from citizen and NZ Department of Conservation database. The main objectives were to a) detect trends and assess historical and present occurrence of migratory humpbacks in the region; and b) compare, when possible, the Whangaparapara and Tory Channel data sets. Between 1956 and 1962, Whangaparapara station captured 317 humpbacks, with 88.6% (n=281) of individuals taken during the northern migration. Males and females represented 69.5% (n=194) and 75% (n=27) of the catch during the northern and southern migration, respectively. Females with near term foetuses (n=10) were only caught during the former. Large catches in 1959 (32.8%, n=104) and 1960 (42.6%, n=135) in austral winter suggest that the North Island East coast was an important historic migration route. All whales captured during the southern migration (n=36) revealed prey items in their stomachs. These whaling records provide the first evidence of opportunistic feeding within NZ waters. Additionally, twenty four opportunistic sightings recorded between 1978 and 2011, indicate that humpbacks can transit through the Hauraki Gulf during any month of the year. This study provides new insights to historical migratory behaviour and distribution of humpbacks in NZ waters, which are important to ensure the conservation and recovery of this remnant population.
Date : December 2013