Central West Coast, North Island IMMA
Size in Square Kilometres
15,626 km2
Qualifying Species and Criteria
Māui dolphin – Cephalorhynchus hectori maui
Criterion A; B (1)
Other Marine Mammal Species Documented
Delphinus delphis, Orcinus orca, Tursiops truncatus
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Summary
These nearshore waters, delineated by the 100m depth contour encompass the New Zealand West Coast North Island Marine Mammal Sanctuary and includes the coastal harbours. These turbid waters are the preferred habitat for endemic Cephalorhynchus dolphins. The area encompasses the known current habitat of the IUCN Red Listed Critically Endangered Māui dolphin (Cephalorhynchus hectori maui) and protects the important potential for distribution of the sister-taxa, Hector’s dolphins (Cephalorhynchus hectori hectori) (listed as Endangered by IUCN) from the South Island. The area is also used by transient common bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca). Common dolphins (Delphinus delphis) use the more offshore waters for feeding (although occasionally are closer to shore if there are schooling fishes inshore). They are subject to fisheries bycatch pressure in particular off this coast including northern Taranaki waters.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
This IMMA includes the only currently occupied year-round habitat of Critically Endangered (IUCN Red List) Māui dolphins (Oremus et al. 2012, Derville et al. 2016, Constantine et al. 2021, Roberts et al. 2019a). Their current range is extremely limited compared to their historical range (Dawson et al. 2001). Māui dolphins have been isolated by ~15,000 years from the South Island Hector’s dolphins (Baker et al. 2002) and their unique haplotype most likely resulted from a population bottleneck and small home range (Oremus et al. 2012, Pichler & Baker 2000). Their core range has decreased since the 1970s (Russell 1999, Constantine et al. 2021).
Criterion B: Distribution and Abundance
Sub-criterion B1: Small and Resident Populations
The entire known range of the Māui dolphin is included in this IMMA. This is a small population (54 dolphins aged 1+ 95% CI – 48-66) facing threats from disease and fisheries bycatch (Constantine et al. 2021, Cooke et al. 2018, Roberts et al. 2019a, Roberts et al. 2021). Individuals have small home ranges averaging 35.5 km, with a maximum range of 80 km recorded for one individual (Oremus et al. 2012). A genetic and photo-identification database has identified dolphins up to 20 years after their initial identification highlighting long-term site fidelity. In 2010, there were two female Hector’s dolphins genetically identified swimming with Māui dolphins within this IMMA; one of the females was identified again in 2011 and 2020 so remained with the Māui dolphins (Hamner et al. 2014, Constantine et al. 2021). This was considered an extraordinary event, but in 2015 and 2020, two different male Hector’s dolphins were also genetically identified with Māui dolphins suggesting long-range movements by Hector’s dolphins from the South Island may become a more regular occurrence (Constantine et al. 2021). Surveys have been mostly conducted in summer months with neonates and calves observed in this region. Groups containing calves are larger than non-calf groups. These nursery groups contain male and female adults which differs from Hector’s dolphins (Oremus et al. 2012).
Supporting Information
Abraham, E.R., Neubauer, P., Berkenbusch, K., Richard, Y. 2017. Assessment of the risk to New Zealand marine mammals from commercial fisheries. New Zealand Aquatic Environment and Biodiversity Report No. 189, Ministry for Primary Industries, Wellington, New Zealand
Baker, A.N., Smith, A.N.H., Pichler, F.B. 2002. ‘Geographical variation in Hector’s dolphin: recognition of new subspecies of Cephalorhynchus hectori’. Journal of The Royal Society of New Zealand 32: 713-727
Baker, C.S., Boren, L., Childerhouse, S., Constantine, R., van Helden, A., Lundquist, D., Rayment, W., Rolfe, J.R. 2019. Conservation status of New Zealand marine mammals, 2019. New Zealand Threat Classification Series 29. Department of Conservation, Wellington, New Zealand, pp 18
Constantine, R., Steel, D., Carroll, E., Hansen, C., Hickman, G., Hillock, K., Ogle, M., Tukua, P., Baker, C.S. 2021. Estimating the abundance and effective population size of Maui dolphins using microsatellite genotypes in 2020-21, with retrospective matching to 2001. Final Report to the Department of Conservation, Wellington, New Zealand
Cooke, J.G., Steel, D., Hamner, R., Constantine, R., Baker, C.S. (2018). Population estimates and projections of Māui dolphin (Cephalorhyncus hectori maui) based on genotype capture–recapture, with implications for management of mortality risk. Report to the 2018 International Whaling Commission, SC/67b/ASI. 15 p.
Dawson, S., Pichler, F., Slooten, E., Russell, K., Baker, C.S. 2001. ‘The North Island Hector’s dolphin is vulnerable to extinction’. Marine Mammal Science 17: 366-371
Derville, S., Constantine, R., Baker, C.S., Oremus, M., Torres, L.G. 2016. ‘Environmental correlates of nearshore habitat distribution by the Critically Endangered Māui dolphin’. Marine Ecology Progress Series 551: 261-275
Hamner, R.M., Constantine, R., Oremus, M., Stanley, M., Brown, P., Baker, C.S. 2014. ‘Long-range movement by Hector’s dolphins provides potential genetic enhancement for critically endangered Maui’s dolphin’. Marine Mammal Science 30: 139-153
Miller, E., Dawson, S., Ratz, H., Slooten, E. 2013. ‘Hector’s dolphin diet: The species, sizes and relative importance of prey eaten by Cephalorhynchus hectori, investigated using stomach content analysis’. Marine Mammal Science 29: 606-628
Ogilvy, C., Constantine, R., Bury, S.J., Carroll, E.L. 2022. Diet variation in a critically endangered marine predator revealed with stable isotope analysis. Royal Society Open Science 9:220470
Oremus, M., Hamner, R.M., Stanley, M., Brown, P., Baker, C.S., Constantine, R. 2012. ‘Distribution, group characteristics and movements of the Critically Endangered Maui’s dolphin Cephalorhynchus hectori maui’. Endangered Species Research 19: 1-10
Pichler, F.B., Baker, C.S. 2000. ‘Loss of diversity in the endemic Hector’s dolphin due to fisheries-related mortality’. Proceedings of the Royal Society of London B 267: 97-102
Rayment, W., Dawson, S., Scali, S., Slooten, L. 2011. ‘Listening for a needle in a haystack: passive acoustic detection of dolphins at very low densities’. Endangered Species Research 14:149-156
Roberts, J.O., Webber, D.N., Roe, W.D., Edwards, C.T.T., Doonan, I.J. 2019a. 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
Roberts, J., Constantine, R., Baker, C.S. 2019b. Population effects of commercial fishery and non-fishery threats on Māui dolphins (Cephalorhynchus hectori maui). New Zealand Aquatic Environment and Biodiversity Report No. 215. Fisheries New Zealand, Wellington, New Zealand, pp. 18
Roberts, J.O., Jones, H.F.E., Roe, W.D.. 2021. The effects of Toxoplasma gondii on New Zealand wildlife: implications for conservation and management. Pacific Conservation Biology 27:208-220
Russell, K. 1999. The North Island Hector’s Dolphin: A Species in Need of Conservation. MSc Thesis. Auckland: University of Auckland
Stephenson, F., Goetz, K., Sharp, B.R., Mouton, T.L., Beets, F.L., Roberts, J., MacDiarmid, A.B., Constantine, R., Lundquist, C.J. 2020. ‘Modelling the spatial distribution of cetaceans in New Zealand waters’. Diversity and Distributions DOI: 10.1111/ddi.13035
Stockin, K.A., Amaral, A.R., Latimer, J., Lambert, D.M., Natoli, A. 2014. ‘Population genetic structure and taxonomy of the common dolphin (Delphinus sp.) and its southernmost range limit: New Zealand waters’. Marine Mammal Science 30: 44-63
