Marlborough's diverse dolphin population
Monday, 26 February 2018
With Seaweek fast approaching, now is a good time to celebrate our most loved ocean-dwelling species – dolphins.
The Marlborough region is lucky to be home to five species of dolphin and you'll be able to see them frequently if you are out on the water.
A pod of killer whale or orca has recently been seen in Queen Charlotte Sound. This was a pretty exciting sighting, given that orca are classified as nationally critical in New Zealand with less than 200 individuals.
Despite their confusing name, orca are biologically classed as dolphins, not whales. It is the largest member of the dolphin family with some males growing as big as 5.5 tonnes. The male's dorsal fin is an impressive 2 metres high.
**READ MORE:
* Orca spotted in Queen Charlotte Sound
* Dolphins 'harrassed' in the sounds
* Much-loved dolphin returns to French Pass**
Because they are so rare, orca have been included in the definition of whales in the Marine Mammals Protection Regulations.
The main regulation that we find people inadvertently breach is that vessels should not approach within 50 metres of a whale. This can be tricky when the orca comes to you! If you can't move out of its path to maintain a distance of 50 metres, put your vessel in neutral and enjoy the show until the orca departs, as it can be more hazardous for the orca if you attempt to reverse away.
The bottlenose dolphin is also distinctive by its size, with adults reaching nearly 4 metres long. The bottlenose is one of our rarest dolphins, with fewer than 1000 in New Zealand waters.
There are three genetically distinct populations (450 in Bay of Islands, less than 70 in Fiordland, and around 400 in Marlborough Sounds-Westport), making these populations even more under threat. Bottlenose dolphins are calving in the sounds at this time of year so they are highly vulnerable to boat strike and disturbance to feeding calves.
The so-called common dolphins are not-so-common in Marlborough. Their stronghold is in the Hauraki Gulf, Bay of Islands and Bay of Plenty. They often migrate through Cook Strait, and are occasionally seen in the Sounds.
Seen in their thousands all year round in Kaikōura, with a smaller number in the sounds over winter, dusky dolphins are probably our most acrobatic dolphin species.
Their repertoire of tricks includes head-over-tail leaps, backslaps, headslaps, tailslaps and spins. These eye-catching displays are believed to help synchronise co-operative foraging.
And finally, our tiniest dolphin, the Hector's dolphin. They reach no more than 1.5 metres in length and can be easily identified by their 'mickey mouse ear' shaped dorsal fin. There are about 1000 in Clifford and Cloudy bays, but only 30-40 reside in Queen Charlotte Sound.
Watching dolphins is a joy to most people. However, what we can't see from our boat are the actions of the dolphins underwater.
Dolphins will often feed co-operatively, spending considerable time and energy rounding up fish into a ball. Members of the pod will take turns at maintaining the ball, while the others pick off the fish on the outside.
This feeding tactic increases their efficiency at catching prey. However, getting too close in your boat has the obvious impact of scattering the fish and wasting their efforts.
The best way to view dolphins is to approach slowly, stop no closer than 50 metres and turn your engine to neutral. Sit back and enjoy the show. It's not unheard of for dolphins to use a boat as a tool in their herding.