Dolphin sightings, Tasman bay to Cook Strait, New Zealand, September 1968‐June 1969 (note)

Abstract

Abstract Seventy‐one schools of dolphins were sighted, in which four species were identified: common dolphin, Delphinus delphis Linn.; dusky dolphin, Lagenorhyn‐rhus obscurus (Gray); bottlenose dolphin, Tursiops truncatus (Montagu); and Hector's dolphin, Cephalorhynchus hectori (van Beneden). Of the 71 schools, 37 were of common dolphin, 12 of dusky, 12 of bottlenose, and 5 of Hector's; and 5 were mixed (4 schools of common + dusky; and 1 of these two + bottlenose). Sightings of albino specimens of common and bottlenose dolphin are recorded, and copulation is described for these species. Scarcity of summer sightings of common and dusky dolphin is related to observations of large, apparently migratory schools elsewhere in New Zealand waters during this season. Observations on all four species revealed a mean sustained swimming speed of around 15–18 km.h‐1, and a maximum of 36km.h‐1. Common dolphin were observed to spout for air at 6–10 s intervals, with occasional longer dives of 15–20 s. Sea surface temperatures in the range 9.5–20.0°c are plotted as seasonal ranges in the Tasman Bay, Marlborough Sounds, and Cook Strait areas respectively, and are related to the presence or apparent absence of each species.