Habitat Modification and Destruction
In the past, this has been much less of a problem in New Zealand than in more heavily populated countries. However, substantial parts of the local marine environment have been changed dramatically through port developments, reclamations and other uses like aquaculture. And there are several major developments that may make habitat change a serious problem for marine mammals in New Zealand waters.

Mussel farming for example, has expanded rapidly in New Zealand and is competing for habitat with several whale and dolphin populations. The Trust has carried out several assessments of the effects of aquaculture on marine mammal populations (see below).

Marine mining is another activity that could threaten New Zealand marine mammals. For example, there are plans for sand mining throughout the range of the North Island Hector’s dolphin or Maui’s dolphin. Typically, it takes between one and three years for the plants and animals that live in and on the sand to recover to the same distribution and total numbers after a sand mining operation. However, it can take much longer for the community composition to recover. For example, the removal of some organisms and crushing of others tends to attract scavengers into the area, changing the local ecology. Proposals for gold mining off the South Island West Coast would include exploration in sandy and muddy marine environments as well as drilling into solid rock.

Energy use is another issue starting to encroach on marine environments in New Zealand. There are proposals for major oil and gas exploration as well as tidal energy generation. Some of these proposals are in habitats critical to Hector’s dolphin.

Publications and reports

• Slooten, E., Rayment, W.J. and Webster, T. Report to Pegasus Bay Marine Farms and Department of Conservation on potential impacts of marine farms on marine mammals: existing research data, information gaps and problems with monitoring (2005)
• Slooten, E., Rayment, W., DuFresne, S. and Clement, D. Whales and dolphins of the Marlborough Region: Distribution, human impacts and management considerations. Report for Marlborough Regional Council (2002)
• Slooten, E. Hearing evidence on potential effects of mussel farming on the whales and dolphins of the North Otago coastline. For Otago Regional Council Hearing (2002).
• Slooten, E. Conservation Management in the face of uncertainty: Effectiveness of four options for managing Hector’s dolphin bycatch. Presented at NZ Marine Sciences Society Conference, International Marine Mammal Conference (San Diego) and IUCN workshop to review red list of threatened marine mammal species (2007)
• Dawson, S.M. and Slooten, E. Management of gillnet bycatch of cetaceans in New Zealand.  Journal of Cetacean Research and Management  7: 59-64 (2005)
• Slooten, E., Battersby, Z. and Battersby, L. 2001. Potential effects of mussel farming on Hector’s dolphins in Queen Charlotte Sound. Report for Marlborough District Council.
• Slooten, E., Dawson, S.M. and DuFresne, S. 2001. Report on interactions between Hector’s dolphins (Cephalorhynchus hectori) and a Golden Bay mussel farm. Report for Environment Canterbury.
• Slooten, E., DuFresne, S. and Clement, D. 2000. Potential effects of mussel farming on Hector’s dolphins in the Banks Peninsula region. Report for Environment Canterbury.
• Slooten, E., Rayment, W., Clement, D. Jones, G. and DuFresne, S. 2000. Report on the potential effects on Hector’s dolphins of proposed mussel farming in Akaroa Harbour. Report for National Institute of Water and Atmosphere.
• Clement, D., Jones, G. and Slooten, E. 1999. Report on the potential effects of mussel farming in Clifford Bay on the Hector’s dolphin population in the area. Report for Clifford Bay Marine Farms Ltd.

For a list of general Trust associated publications and reports on marine mammals and marine mammal ecology, click here. To find out about the people involved in this research, see the University of Otago Marine Mammal Research Group web site.