Line-transect survey of Hector's dolphin abundance between Farewell Spit-Motunau and Timaru-Long Point

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Line-transect survey of Hector's dolphin abundance between Farewell Spit and Motunau (PDF, 484 K)

Line-transect survey of Hector's dolphin abundance between Timaru and Long Point (PDF, 708 K)

Summary

These repors summarises the results of line-transect surveys undertaken in 1999/2000 to quantify the abundance of Hector's dolphins (Cephalorhynchus hecotri) in the coastal area

Between Farewell Spit and Motuanu, along the north-east coast of the South Island, New Zealand, a total of 23 sightings were recorded in 766 km of trackline. Greatest dolphin densities were found within Queen Charlotte Sound, Cloudy and Clifford Bays, and between Cape Campbell and Motunau, South Island, New Zealand. No sightings were reported within Golden Bay or Tasman Bay, within Pelorus Sound, or seaward of the Marlborough Sounds. The total corrected abundance estimate for the survey area (to 4n.m. offshore) is 285 dolphins (95% CI = 137- 590).

Between Timaru and Long Point, along the east coast of the South Island, a total of 27 sightings were made in 437 km of trackline. Greatest dolphin densities were found in Te Waewae Bay, and between Timaru and Oamaru. No sightings were made off the SE coast between Karitane (north of Dunedin) and Colac Bay (west of Bluff), and no sightings were made on any of the offshore transects extending from 4 to 10 nautical miles offshore. 

Simultaneous boat and helicopter surveys were conducted off the south side of Banks Peninsula to measure the combined effect of dolphins being attracted to the survey vessel and observers missing sightings. Correcting for attraction and missed sightings results in a downward revision of abundance estimates by 50%. The total abundance estimate, summing all three surveys  is 1882 dolphins (95% CI= 1246-2843).