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Fishery Bulletin 102(3) 



proportion of dolphins detected within the strip, was 

 estimated. A current, more robust estimate is needed 

 for management. This study describes line-transect 

 boat surveys conducted to estimate Hector's dolphin 

 abundance on the north, east, and south coasts of the 

 South Island of New Zealand. 



Figure 1 



Photograph of the observer platform on the catamaran Cat 



Materials and methods 



Vessel choice and field methods 



Displacement catamarans are inherently suitable for 

 inshore surveys because of their resistance to rolling 

 and their ability to sustain reasonably high cruising 

 speeds with modest power. We based our 

 surveys from a 15.3-m sailing catama- 

 ran (RV Catalyst), which is powered by 

 two 50-hp diesel engines, and cruises 

 at 9-10 knots while using <10 liters of 

 fuel per hour. We fitted a collapsible 

 aluminum sighting platform (~6 m eye 

 height; Fig. 1) to increase the resolution 

 with which observers could measure the 

 downward angles to sightings (see Lerc- 

 zak and Hobbs, 1998. for details) and to 

 allow the observers to see animals far- 

 ther away. The surveys were conducted 

 with a crew of six (five observers, one 

 skipper). 



Three people stood on the platform at 

 any given time; one scanned the surface 

 waters to the right of the platform, and 

 the other scanned to the left, and a third 

 person (the recorder) recorded sightings 

 dictated by the observers. Sightings 

 made by the recorder were not used in 

 our analyses because his or her sight- 

 \Jj ^ ing effort was unavoidably uneven (the 



recorder could not make sightings while 

 recording another sighting). The record- 

 er did not point out sightings to observ- 

 ers. Observers and data recorder rotated 



alyst 



