Rakiura Stewart Island and Te Ara a Kiwa IMMA
Size in Square Kilometres
Qualifying Species and Criteria
Antarctic blue whale – Balaenoptera musculus intermedia
Criterion A; C (3)
Fin whale – Balaenoptera physalus
Hector’s dolphin – Cephalorhynchus hectori
Criterion A; B (1)
Humpback whale – Megaptera novaeangliae
Criterion A; C (3)
New Zealand fur seal – Arctocephalus forsteri
Criterion C (1)
New Zealand sea lion – Phocarctos hookeri
Criterion A; B (1); C (1)
Pygmy blue whale – Balaenoptera musculus brevicauda
Criterion A; C (3)
Sei whale – Balaenoptera borealis
Southern right whale – Eubalaena australis
Criterion C (1, 3)
Sperm whale – Physeter macrocephalus
Marine Mammal Diversity
Criterion D (2)
Berardius arnuxii, Balaenoptera bonaerensis, Delphinus delphis, Lagenorhynchus obscurus, Orcinus orca, Hydrurga leptonyx, Globicephala melas, Caperea marginata, Mirounga leonine, Lissodelphis peronii
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Covering the southern coast of Te Waipounamu/South Island, Te Ara a Kiwa/Foveaux Strait, and the waters around Rakiura/Stewart Island, this IMMA has a wide range of marine mammal habitats from terrestrial haul out sites to shallow, coastal shelf waters to deep, off the shelf waters. Twenty one species or subspecies have been recorded in the IMMA including eight threatened marine mammals: Critically Endangered Antarctic blue whales, Endangered Hector’s dolphins, New Zealand sea lion, pygmy blue whale, humpback whale (Oceania sub-population), and sei whale, as well as Vulnerable fin whale and sperm whales. The IMMA contains the third largest breeding area for the endemic New Zealand sea lion and a small, genetically distinct population of endemic Hector’s dolphins. The IMMA is also an important migratory route for blue, southern right and humpback whales. The deeper waters to the west support sperm and beaked whales including frequent sightings and strandings of Arnoux’s beaked whales.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
There are eight species or subspecies found in the IMMA that meet this criterion with IUCN threatened or vulnerable status, and include Antarctic blue whale Balaenoptera musculus intermedia (CR), Hector’s dolphin Cephalorhynchus hectori (EN), New Zealand sea lion Phocarctos hookeri (EN), pygmy blue whale Balaenoptera musculus brevicauda (EN), humpback whale Megaptera novaeangliae (Oceania sub-population; EN), sei whale Balaenoptera borealis (EN), fin whale Balaenoptera physalus (VU), and sperm whale Physeter macrocephalus (VU). All these species have been reported from the IMMA (e.g. DOC Marine Mammal Sighting and Stranding database 2020) and this IMMA forms an important part of their range within New Zealand.
Criterion B: Distribution and Abundance
Sub-criterion B1: Small and Resident Populations
New Zealand sea lions are slowly recovering within the IMMA with a new, small breeding colony established in Port Pegasus, on the south eastern coast of Rakiura, which is now the fifth largest breeding population of this endangered, endemic species with an estimate of 178 (168-194) adults and pups in 2014-2015 (Roberts & Doonan 2016). There are also a small number of additional breeding females in the Catlins (e.g. northeastern part of the IMMA). The total number of New Zealand sea lions within the IMMA is presently estimated at approximately 300-400 individuals (S. Childerhouse pers. comm.). The turbid coastal waters along the South Island coast including three large bays within the IMMA (i.e. Te Waewae, Toetoes and Porpoise Bays) form part of a small, endemic and genetically distinct sub-population of Hector’s dolphins, called the South Coast South Island sub-population (Hamner et al. 2012). These three bays are spread over approximately ~120 km of coastline but dolphins at all three sites consistently exhibit a high degree of genetic differentiation from the two other South Island sub-populations of Hector’s dolphins (Hamner et al. 2012). An aerial survey estimated a total of 332 (95% CI 217-508) Hector’s dolphins along the south coast of the South Island (e.g. the whole area is contained within the IMMA) (MacKenzie & Clement 2018), providing evidence that this sub-population is extremely vulnerable.
Criterion C: Key Life Cycle Activities
Sub-criterion C1: Reproductive Areas
Important New Zealand fur seal breeding colonies (e.g. Ruapuke Island, Bench Island, Breaksea Island, Codfish Is, Solander Island) occur on offshore Islands around Te Ara a Kiwa and Rakiura (Baird 2011) whose coastal and offshore feeding (particularly for nursing females) are constrained to feeding completely within the IMMA during the breeding season (MPI 2017). Also, as noted previously, there are important New Zealand sea lion breeding areas at Port Pegasus, Rakiura (the third largest colony for this endangered, endemic) and the Catlins on the North Island. The highest concentration of records of southern right whales are from Te Ara a Kiwa with a local hot spot in Te Waewae Bay. Te Waewae Bay was the site of the first recorded mating of southern right whales around New Zealand post commercial whaling operations and is also a site of regular records of cow-calf pairs (Carroll et al. 2014, Cranswick et al. 2022).
Sub-criterion C3: Migration Routes
Historical whaling data confirms this IMMA as an important migration route for humpback whales (Dawbin 1956) sperm whales (Gaskin 1973) and southern right whales (Richards et al. 2009, Carroll et al. 2014), and efforts to research this important migratory route has been undertaken for humpback whales (Gibbs & Childerhouse 2000, Constantine & Riekkola 2019), sperm whales (Gaskin 1973) and southern right whales (Carroll et al. 2014, Mackay et al. 2020). Recent satellite tracking of blue whales and southern right whales), have also further confirmed that this IMMA still contains important migratory pathways for these species (Carroll et al. 2013, Goetz et al. 2018, Mackay et al. 2020, DOC Marine Mammal Sighting and Stranding database 2020).
Criterion D: Special Attributes
Sub-criterion D2: Diversity
This IMMA supports 21 different marine mammal species or subspecies recorded (e.g. DOC Marine Mammal Sighting and Stranding database 2020) and the presence of other unrecorded species highly likely. The IMMA is an important migratory route for humpback whales (Gibbs & Childerhouse 2000, Constantine & Riekkola 2019), sperm whales (Gaskin 1973) and southern right whales (Carroll et al. 2014, Mackay et al. 2020). Whilst little is known about living pilot whales in New Zealand, Rakiura is a renowned stranding site for pilot whales, including 100+ individuals, with the number of strandings increasing (Oremus et al. 2013, Betty et al. 2019). Seasonally enhanced productivity in this region may influence pilot whale occurrence (Hamilton et al. 2019) and changes in temperature (Shears & Bowen 2017) and ocean dynamics may be contributing to increased habitat use by them. The combination of shallow, coastal shelf waters and deep, submarine canyon waters provide ideal habitat for a number of other cetaceans with regular sightings of Arnoux’s beaked whales, pygmy right whales, sperm whales. There are increasing reports of leopard seals on Rakiura and the southeast coast of the South Island (Hupman et al. 2020).
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Betty, E.L., Bollard, B., Murphy, S., Ogle, M., Hendriks, H., Orams, M.B., and Stockin, K.A. 2019 Using emerging hotspot analysis of stranding records to inform conservation management of a data-poor cetacean species. Biodiversity and Conservation 29: 643-665
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Hamner, R.M., Pichler, F.B., Heimeier, D., Constantine, R., and Baker, C.S. 2012. Genetic differentiation and limited gene flow among fragmented populations of New Zealand endemic Hector’s and Maui’s dolphins. Conservation Genetics 13: 987-1002
Hupman, K., Visser, I.N., Fyfe, J., Cawthorn, M., Forbes, G., Grabham, A.A., Bout, R., Mathias, B., Benninghaus, E., Matucci, K., Cooper, T., Fletcher, L., and Godoy, D. 2020. From Vagrant to Resident : occurrence, residency, and births of leopard seals (Hydrurga leptonyx) in New Zealand waters. New Zealand Journal of Marine and Freshwater Research 54 :1-23
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Neumann, D.R. 2001. Seasonal movements of short beaked common dolphins (Delphinus delphis) in the north-western Bay of Plenty, New Zealand: influence of sea surface temperature and El Niño / La Niña. New Zealand Journal of Marine and Freshwater Research 35: 371-374.
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Oremus, M., Gales, R., Kettles, H., and Baker, C.S. 2013. Genetic evidence of multiple matrilines and spatial distribution of kinship bonds in mass strandings of long-finned pilot whales, Globicephala melas. Journal of Heredity 104: 301-311
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