|Our Research/Fishing Impacts
||last updated 18 May 2002
Mortality in gillnets (and to a lesser extent trawling) is a serious
problem for whale and dolphin populations in many parts of the world.
In New Zealand, bycatch in gillnets is threatening several Hectors
Dolphin bycatch in gillnets is one of the Trusts main research
projects. Our ground-breaking research on the Hectors dolphin
population at Banks Peninsula showed that bycatch in gillnets was
unsustainable, and led to the creation of the Banks Peninsula Marine
Mammal Sanctuary. Later research has shown that substantial numbers
of dolphins are still caught immediately north, south and offshore
of the sanctuary. A major focus of our current research, therefore,
is on assessing these impacts.
Based on these studies, we actively promote the extension the boundaries
of the Banks Peninsula sanctuary, and the need to create sanctuaries
in other areas where bycatch is unsustainable. The most urgent issue
at the moment is the critically endangered
Hectors dolphin population off the west coast of the North
Our research on the effects of bycatch has included population
surveys around the South Island and off the North Island west coast,
to estimate population size. Without an accurate population estimate
it is not possible to assess the risks caused by bycatch. We are
also actively involved in research on survival, reproductive rate,
movements, habitat requirements and risk analyses to assess the
effects of bycatch on Hectors dolphins around the country.
Publications and reports
- Dawson, S.M. 2002. Cephalorhynchus dolphins.
pp. 200-203 In: Encyclopedia of Marine Mammals (Perrin,
W.F., Würisg, B. & Thewissen, J.G.M, eds.). Academic
Press. San Diego. (2002) [ISBN 0-12-551340-2].
- Fletcher, D., Dawson, S. and Slooten, E.
Designing a mark-recapture study to allow for local emigration.
Journal of Agricultural, Biological and Environmental Statistics
- Pichler, F.B. Slooten, E. & Dawson, S.M.
Hectors dolphins and fisheries in NZ: a species at risk?
Marine mammals and humans: towards a sustainable balance. N. Gales,
M. Hindell & R. Kirkwood (eds), Melbourne University Press
- Slooten, E., Dawson, S. and Rayment, W. Quantifying
abundance of Hectors dolphins between Farewell Spit and
Milford Sound. Published client report on contract 3076, funded
by Conservation Services Levy. Department of Conservation, Wellington
http://csl.doc.govt.nz/ dsis35.pdf (2002).
- Clement, D., Slooten, E., Dawson, S. and
DuFresne, S. Line-transect survey of Hectors dolphin abundance
between Farewell Spit and Motunau. Published client report on
contract 3075, funded by Conservation Services Levy. Department
of Conservation, Wellington, http://csl.doc.govt.nz/CSL3075.pdf
- Dawson, S., Pichler, F., Slooten, E., Russell,
K. and Baker, C.S. The North Island Hectors dolphin is vulnerable
to extinction. Marine Mammal Science 17 (2): 366-371 (2001).
- Dawson, S.M. 2001. Fine-scale abundance estimates
from the 2000/2001 aerial survey of Hectors dolphins on
the South Island west coast. DOC Science Internal Series 21. 9pp.
Department of Conservation, Wellington.
- DuFresne, S., Dawson, S.M. and Slooten, E.
Line-transect survey of Hectors dolphin abundance between
Timaru and Long Point, and effect of attraction to survey vessel.
Published client report on contract 3074, funded by Conservation
Services Levy. Department of Conservation, Wellington, http://csl.doc.govt.nz/CSL3074.pdf
- Dawson, S., DuFresne, S., Slooten, E. and
Wade, P. Line-transect survey of Hectors Dolphin abundance
between Motunau and Timaru. Published client report on contract
3072, funded by Conservation Services Levy. Department of Conservation,
Wellington, http://csl.doc.govt.nz/CSL3072.pdf (2000).
- Slooten, E., Fletcher, D. and Taylor, B.L.
Accounting for uncertainty in risk assessment: Case study of Hector's
dolphin mortality due to gillnet entanglement. Conservation Biology
14: 1264-1270 (2000).
- Cameron, C., Barker, R., Fletcher, D., Slooten,
E. and Dawson, S. Modelling survival of Hectors dolphins
around Banks Peninsula, New Zealand. Journal of Agricultural,
Biological and Environmental Statistics 4(2): 126-135 (1999).
- Martien, K.K., Taylor, B.L., Slooten, E.
and Dawson, S. A sensitivity analysis to guide research and management
for Hectors dolphin. Biological Conservation 90: 183-191
- Dawson, S.M., Read, A. and Slooten, E. Pingers,
porpoises and power: Uncertainties with using pingers to reduce
bycatch of small cetaceans. Biological Conservation 84(2): 141-146
- Pichler, F., Baker, C.S., Dawson, S.M. and
Slooten, E. Geographic isolation of Hectors dolphin populations
described by mitochondrial DNA sequences. Conservation Biology
12(3): 676-682 (1998).
- Slooten, E. and Dawson, S.M. Conservation
of marine mammals in New Zealand. Pacific Conservation Biology
2: 64-76 (1995).
- Dawson, S.M. The potential for reducing entanglement
of dolphins and porpoises with acoustic modifications to gillnets.
Reports of the International Whaling Commission. Spec. Issue 15:
- Dawson, S.M. and Slooten, E. Conservation
of Hectors dolphins: The case and process which led to establishment
of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation:
Marine and Freshwater Ecosystems 3: 207-221 (1993).
- Slooten, E., Dawson, S.M. and Lad, F. Survival
rates of photographically identified Hector's dolphins from 1984
to 1988. Marine Mammal Science 8(4): 327-343 (1992).
- Dawson, S.M. Clicks and Communication: The
behavioural and social contexts of Hector's dolphin vocalisations.
Ethology 88(4): 265-276. 1991.
- Dawson, S.M. Incidental catch of Hector's
dolphins in inshore gillnets. Marine Mammal Science 7(3): 283-295.
- Dawson, S.M. Modifying gillnets to reduce
entanglement of cetaceans. Marine Mammal Science 7(3): 274-282.
- Slooten, E. and Lad, F. Population biology
and conservation of Hector's dolphin. Canadian Journal of Zoology
69: 1701-1707 (1991).
- Thorpe, C.W., Bates, R.H.T. and Dawson, S.M.
Intrinsic echolocation capability of Hector's dolphin Cephalorhynchus
hectori. Journal of the Acoustical Society of America 90(6): 2931-2934.
- Dawson, S.M. and Thorpe, C.W. A quantitative
analysis of the acoustic repertoire of Hector's dolphin. Ethology
86: 131-145. 1990.
- Dawson, S.M. The high-frequency sounds of
free-ranging Hector's dolphins Cephalorhynchus hectori. Reports
of the International Whaling Commission Special issue 9: 339-344.
- Dawson, S.M. and Slooten, E. Hector's Dolphin
Cephalorhynchus hectori : Distribution and abundance. Reports
of the International Whaling Commission, Special Issue 9: 315-324
For a list of general Trust associated publications and reports
on marine mammals and marine mammal ecology, click
here. To find out about some of the people involved in this
research, see the Univerisity
of Otago Marine Mammal Research Group web site.