New Zealand Journal of Marine and Freshwater Research abstracts
Offshore distribution of Hector’s dolphins at Banks Peninsula, New Zealand:
is the Banks Peninsula Marine Mammal sanctuary large enough?
ELISABETH SLOOTEN1
WILLIAM RAYMENT1,2
STEVE DAWSON2
Departments of Zoology1 and Marine Science2
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: Liz.Slooten@stonebow.otago.ac.nz
Abstract Aerial surveys of Hector’s dolphins were carried out to
evaluate the effectiveness of the Banks Peninsula Marine Mammal Sanctuary.
In summer, the proportion of sightings inside the 4 nautical mile offshore
boundary of the sanctuary was 79%. This dropped to just over 35% in winter.
These estimates were used in a population viability analysis to determine whether
the sanctuary needs to be extended to reduce dolphin bycatch to sustainable
levels. We followed the standard procedure for setting limits on marine mammal
bycatch in the United States to calculate a bycatch limit of 1.6 or 2.8 dolphins
per year (depending on whether the sanctuary population is included). If the
offshore boundary was extended to 15 nautical miles, the sanctuary would need
to be extended alongshore north and south by more than 30 nautical miles to
reduce bycatch to 2.8, or north and south by 60 nautical miles to reduce bycatch
to 1.6 dolphins per year.
Keywords aerial survey; Hector’s dolphin; Banks Peninsula Marine
Mammal Sanctuary; gill-net entanglement; bycatch; sustainability; effective
survey design
New Zealand Journal of Marine and Freshwater Research,
2006, Vol. 40: 333–343
0028–8330/06/4002–0333 © The Royal Society of New Zealand
2006
M04148; Online publication date 3 May 2006. Received 1 November 2004; accepted
13 January 2006
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