Hikurangi Trench IMMA

Size in Square Kilometres

50,546 km2

Qualifying Species and Criteria

Marine Mammal Diversity 

Criterion D2 – Diversity

Balaenoptera musculus, Ziphius cavirostris, Balaenoptera physalus, Mesoplodon grayi, Cephalorhynchus hectori, Megaptera novaeangliae, Globicephala melas, Kogia breviceps, Balaenoptera borealis, Physeter macrocephalus, Mesoplodon layardii, Balaenoptera edeni, Tursiops truncatus, Delphinus delphis, Mesoplodon densirostris, Balaenoptera edeni, Orcinus orca, Hydrurga leptonyx, Globicephala melas, Arctocephalus forsteri, Caperea marginata, Globicephala macrorhynchus, Mirounga leonina, Eubalaena australis, Lissodelphis peronii, Stenella coeruleoalba

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The Hikurangi Trench dominates this area, with geologically complex canyon and channel systems fed by the East Cape Current from the north and the productive Wairarapa Eddy from the south (Hadfield, 2007). The area supports an important area for marine mammal diversity. Pygmy sperm whales with a high proportion of mother-calf pairs in the region are reported from strandings data (Baker and van Helden, 1990, Brabyn, 1991). There are other deep-diving species most notably Gray’s, strap-toothed, Cuvier’s, and other beaked whales, sperm whales, and long-finned pilot whales, all of which are well represented in the stranding and sighting records for the region (Gaskin 1973, Betty et al. 2020). The Hikurangi Trench is a southerly extension of the Kermadec Trench incorporating one of the most geologically diverse canyon and channel systems in the world. It is enriched by the East Cape Current (Hadfield et al. 2007). The south travelling East Cape Current and the north flowing component of the Wairarapa Eddy brings nutrient-rich waters to this region. These conditions provide an abundant and important habitat for teuthophagous and deep-diving species including in this region: pygmy sperm whales, sperm whales, Gray’s beaked whales, strap-toothed beaked whales, Cuvier’s beaked whales, other beaked whale species, and long-finned pilot whales.

The Shelf area has coastal dolphin species particularly common and common bottlenose dolphins, and some of the only records of Hector’s dolphins on the east coast of the North Island (Freeman 2003, Gaskin 1968). NZ fur seals are also numerous in the area (Baird 2011). The area appears to be part of a migratory corridor for various species of Balaenopterid possibly following distinctive geophysical features or current systems. Humpback and southern right whales are occasionally seen near shore along this coastline as their numbers around New Zealand are increasing post whaling (Carroll et al. 2014, Dawbin 1956, Riekkola et al. 2018). These species contribute to the overall high species diversity in the area.

Description of Qualifying Criteria

Criterion D: Special Attributes

Sub-criterion D2: Diversity

Limited sightings data and the stranding record indicate the occurrence of 22 cetacean and 3 pinniped species in this IMMA (Brabyn 1991, Baird 2011, New Zealand Department of Conservation (DOC) Marine Mammal Sighting and Stranding database 2020). This represents an exceptional diversity of deep diving cetaceans. There is also a high diversity of other cetaceans including coastal and shelf delphinids (including killer whales, common dolphins, striped dolphin and Hector’s dolphin), and mysticetes including 6 rorqual species, the southern right whale, and the pygmy right whale (Brabyn 1991, Baker and van Helden 1999, Baker 2002, van Helden et al 2002,Thompson et al 2013, Gaskin 1973, Roberts et al 2019, Freeman 2003, Betty et al. 2020, Cranswick et al. 2022, DOC Marine Mammal Sighting and Stranding database 2020). The primary species recorded for the region are pygmy sperm whale, Gray’s beaked whale, strap-toothed beaked whale, and Cuvier’s beaked whale (Baker and van Helden 1990, Thompson et al. 2013). There are numerous records of strandings and sightings of various species of Balaenopteridae (Dawbin 1956, DOC Marine Mammal Sighting and Stranding database 2020). Sighting records of southern right whales are increasing (Cranswick et al. 2022). New Zealand fur seals are common in the region with 2 other pinniped species (i.e. southern elephant seal, leopard seal) regularly recorded from the region. The warm subtropical East Cape Current may explain the occasional records of cetaceans more commonly sighted in tropical waters (e.g. short-finned pilot whale, dense beaked whale).

Supporting Information

Baird, S.J. 2011. New Zealand fur seals – summary of current knowledge. New Zealand Aquatic Environment and Biodiversity Report No. 72. 51 p.

Baker, A.N. 2002. ‘Status, relationships, and distribution of Mesoplodon bowdoini Andrews, 1908 (Cetacea: Ziphiidae)’. Marine Mammal Science 17: 473-493.

Baker, A.N. and van Helden, A.L. 1990. ‘First record of the dwarf sperm whale, Kogia simus (Owen), from New Zealand. National Museum of New Zealand Records’ 3: 125-130.

Baker, A.N. and van Helden, A.L. 1999. ‘New records of beaked whales, Genus Mesoplodon, from New Zealand (Cetacea: Ziphiidae).’ Journal of The Royal Society New Zealand 29: 235-244

Beatson, E. 2007. ‘The diet of pygmy sperm whales, Kogia breviceps, stranded in New Zealand: implications for conservation’. Reviews in Fish Biology and Fisheries 17:295–303 DOI 10.1007/s11160-007-9039-9

Betty, E.L., Bollard, B., Murphy, S., Ogle, M., Hendriks, H., Orams, M.B., Stockin, K.A. 2020. ‘Using emerging hot spot analysis of stranding records to inform conservation management of a data-poor cetacean species’. Biodiversity and Conservation 29: 643-665

Brabyn, M. 1991. An analysis of the New Zealand Whale Stranding record. Science and Research Series No. 29. Department of Conservation, Wellington.

Carroll, E.L., Rayment, W.J., Alexander, A.M., Baker, C.S., Patenaude, N.J., Steel, D., Constantine, R., Cole, R., Boren, L., and Childerhouse, S. 2014. ‘Reestablishment of former wintering grounds by New Zealand southern right whales’. Marine Mammal Science 30: 206-220

Cranswick, A.S.,Constantine, R., Hendricks, H., Carroll, E.L. 2022. Social media and citizen science records are important for the management of rarely sighted whales. Ocean & Coastal Management 226: 106271

Dawbin, W.H. 1956. ‘The migrations of humpback whales which pass the New Zealand coast’. Transactions and Proceedings of the Royal Society of New Zealand 84: 147-196

Freeman, D. 2003. A review of records of Hector’s dolphin (Cephalorhynchus hectori) from the East Cast of the North Island, New Zealand. Department of Conservation Technical Support Series No 11. Department of Conservation, Gisborne, New Zealand.

Gaskin, D. E. 1968. Distribution of Delphinidae (Cetacea) in relation to sea surface temperatures off Eastern and Southern New Zealand. ‘New Zealand Journal of Marine and Freshwater Research 2: 527-534

Gaskin, D.E. 1973. ‘Sperm whales in the western South Pacific’, New Zealand Journal of Marine and Freshwater Research 7: 1-20, DOI: 10.1080/00288330.1973.9515453

Hadfield, M.G., Rickard, G.J., and Uddstrom, M.J. 2007. ‘A hydrodynamic model of Chatham Rise, New Zealand’. New Zealand Journal of Marine and Freshwater Research, 41: 239-264, DOI: 10.1080/00288330709509912

Roberts, J.O., Webber, D.N., Roe, W.D., Edwards, C.T.T., and Doonan, I.J. 2019. Spatial risk assessment of threats to Hector’s and Māui dolphins (Cephalorhynchus hectori). New Zealand Aquatic Environment and Biodiversity Report No. 214. Fisheries New Zealand, Wellington, New Zealand, pp. 168

Riekkola, L., Zerbini, A.N., Andrews, O., Andrews-Goff, V., Baker, C.S., Chandler, D., Childerhouse, S., Clapham, P., Dodemont, R., Donnelly, D., Friedlaender, A., Gallego, R., Garrigue, C., Ivashchenko, Y., Jarman, S., Lindsay, R., Pallin, L., Robbins, J., Steel, D., Tremlett, J., Vindenes, S., and Constantine, R. 2018. ‘Application of a multi-disciplinary approach to reveal population structure and Southern Ocean feeding grounds of humpback whales’. Ecological Indicators 89: 455-465

Thompson, K., Baker, C.S., van Helden, A., Patel, S., Millar, C., and Constantine, R., 2012. ‘The world’s rarest whale’. Current Biology 22: R905–906.

Thompson, K.F., Millar, C.D., Baker, C.S., Dalebout, M., Steel, D., van Helden, A.L., and Constantine, R. 2013. ‘A novel approach provides insights into the management of rare cetaceans’. Biological Conservation 157: 331-340

van Helden, A.L., Baker, A.N., Dalebout, M.L., Reyes, J.C., Van Waerebeek, K., and Baker, C.S. 2002. ‘Resurrection of Mesoplodon traversii (Gray, 1874), senior synonym of M. bahamondi Reyes, Van Waerebeek, Cárdenas and Yáñez, 1995 (Cetacea: Ziphiidae)’. Marine Mammal Science 18: 609–621

New Zealand Department of Conservation (DOC) 2020. Marine Mammal Sighting and Stranding database. Public database maintained by DOC on behalf of New Zealand Government. Available from marinemammals@doct.govt.nz. Accessed in June 2020.


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