Why Kaikoura?

Today there were monster swells in the ocean above the Kaikoura Canyon, and when the wind started to blow hard, we spent the day at anchor southwest of Kaikoura Peninsula taking stock, looking at data, and generally gathering our wits about us.

So, why have we decided to do this work off the Kaikoura coast and not someplace more convenient to Woods Hole? There are very few places in the world where sperm whales can be reliably found close to shore. Kaikoura is one of them. The feature that makes the location so special is the Kaikoura Canyon—an undersea trench that cuts through the continental shelf such that the seabed plunges to depths over 1000 metres within 4 kilometres of the coastline.

A sperm whale heads for the deep waters of the Kaikoura
Canyon to feed. (Will Rayment, University of Otago)

Whales aren't the only marine mammal attracted to the food
supplied by the riches of the canyon. Here, a New Zealand
fur seal. (Will Rayment, University of Otago)

The biological productivity within the canyon is enormous. Scientists have recently revealed that the biomass of seabed-dwelling invertebrates in the Kaikoura Canyon is 100 times greater than in typical deep-sea habitats. Likewise, the densities of bottom-living fish are dramatically higher in the canyon than on the surrounding seafloor.

This presumably makes the Kaikoura canyon a great place to look for food. And sperm whales need a lot of food. They are the largest of the odontocetes, the toothed whales, and probably require up to 1.5 tons of food per day. As we have seen from our DTAG data, they routinely dive to over 1,000 meters looking for their prey, primarily squid and bottom-living fish. Exactly what they eat at Kaikoura remains to be seen and is something we hope to learn from our analyses of their sloughed skin and fecal samples.

But it’s not just sperm whales that make use of the abundant food supply at Kaikoura—a there is a plethora of other marine mammal species that exploit this rich submarine larder, as well. Kaikoura is home to large numbers of dusky dolphins, which can be seen playing and resting in the coastal waters during the daytime before heading offshore to feed at night. Similarly, New Zealand fur seals rest up and bask on the rocky coastline, then swim out over the deep canyon waters to forage. There are a number of more transient visitors, too. So far, during our brief visit we have seen southern right, blue, and killer whales. And the productive waters are a Mecca for seabirds. Every day we are surrounded by albatrosses, petrels, and shearwaters, all looking for a piece of the action.

Seabirds like this Buller's albatross are attracted by the
productivity of the canyon--and the antics of scientists.
(Will Rayment, University of Otago)

The abundance and diversity of marine life makes Kaikoura a great place for scientists to work. Similarly, it’s a big draw for human visitors, and there is now a thriving tourism industry in Kaikoura. People come from far and wide to go whale watching, swim with dolphins, and view the huge variety of seabird species. During our time here we have come to realize just how lucky we are to do what we do in such a special environment.

Further reading:
De Leo et al., "Submarine canyons: Hotspots of benthic biomass and productivity in the deep sea," Proceedings of the Royal Society B 277(2010): 2783-2792.