Te Waewae Bay boat surveys
There have been three vessel based surveys conducted in Te Waewae Bay - two used line transect methods (Dawson et al. 2004) and the most recent one used mark-recapture method (Green et al. 2007, in prep). Both methods can be used to gain a robust population estimate but in the case of Te Waewae Bay are different both in terms of the method and length of study.
The first population estimate of Hector's dolphins in Te Waewae Bay (Dawson & Slooten 1988) was conducted as part of a nationwide coastal strip-transect survey to estimate total abundance of the dolphins. Dawson and Slooten (1988) estimated the population of the bay at approximately 341 dolphins, with no confidence intervals provided.
A later survey in 1998/99 (Dawson et al. 2004) provided a population estimate of Te Waewae bay of 89 dolphins (CV = 0.324; 95% CI = 36-218) as part of a wider study to provide a population estimate for an area between Farewell Spit and Long Point.
Vessel-based surveys were conducted in Te Waewae Bay, Southland during 2004 and 2005. The aims of the study were to provide an abundance estimate and document the distribution of the Hector's dolphin population that used the bay.
Key findings of the study were:
- The study estimated that the population that used Te Waewae Bay in the Autumn of 2004 was 259 (CV = 0.171; 95% CI = 185-361) and in the summer period, 403 (CV = 0.121; 95% CI = 280-488).
- 282 hours were spent on the water over 38 days of study with a total of 2,462 km travelled.
- Dolphin distribution was concentrated along the inshore coastal section of the bay (less than 5.6km from shore) and dolphins were sighted less at the western and eastern extremes of the bay.
- 16.1 % of the sighted dolphins in the Autumn period were sighted further than 5.6 km from shore and in summer 2.1% were sighted further than 5.6 km from shore, showing some indication of seasonal inshore-offshore movement.
Important Note: Due to the considerable difference in the methods between line-transect and mark-recapture surveys, the results do not indicate any trend such as an increase in the Hector's dolphin population of Te Waewae Bay.
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Contacts
To report whale or dolphin sightings or strandings phone the DOC HOTline 24 hour emergency number:
0800 DOC HOTline (0800 362 468)