The North Island of New Zealand is bathed in a subtropical mass of water. Water temperature varies from a low of around 14 degrees Celsius in winter to a high of around 22 degrees Celsius in summer. Visibility ranges from 5 metres to 40 metres depending on the time of year and location. The best visibility is usually from late summer to the end of winter, when there is less plankton in the water.
Unlike tropical reefs, where there is little change between the seasons, New Zealand waters have definite seasons that herald major changes to the reef community. The visibility can sometimes drop to as little as 3 metres during the spring plankton bloom from September to November. However, this explosion of planktonic growth signals many species to spawn, so there are benefits to diving in New Zealand all year round.
The general pattern of fish distributions around New Zealand is modified by ocean currents. The East Auckland Current originates in tropical waters off the east coast of Australia. On its way to New Zealand it passes Lord Howe Island and Norfolk Island, and once here it travels southeast between North Cape and East Cape, parallel to Northland’s east coast. This current brings clear, warm water (about 1-2 degrees Celsius warmer than on the adjacent mainland coast) to the offshore islands and some of the mainland peninsulas and headlands.
Larval and juvenile fishes are transported by the East Auckland Current from subtropical areas to New Zealand. Many of these immigrant fishes do not survive the low water temperatures of their first winter. Some that survive are unable to reproduce while others survive and do go on to reproduce. As such, the diversity of coastal fishes is greatest in the north, where these subtropical species mingle with cooler-water species.
Books to Read
A Guide to New Zealand’s Marine Reserves
By Jenny & Tony Enderby
A Photographic Guide to Sea Fishes of New Zealand
By Wade Doak
Coastal Fishes of New Zealand, An identification guide, Third edition
By Malcolm Francis
New Zealand Coastal Marine Invertebrates, Volume 1
By Steve de C. Cook
Poor Knights Wonderland, Field Guide to the Islands and Marine Reserve
By Glenn Edney
Subtidal Invertebrates of New Zealand, A Divers’ Guide
By Stephen Wing
The Surface of the Sea, Encounters With New Zealand’s Upper Ocean Life
By Iain Anderson
Top New Zealand Dive Sites
By Gillian & Darryl Torckler
Department of Conservation
The Department of Conservation is responsible for New Zealand’s marine reserves. You can find detailed information about each of these reserves on their website as well as information on New Zealand’s marine mammals.
Dive Planet NZ
A growing website with information on anything to do with New Zealand’s marine world.
Ian Skipworth’s Website
Breathtaking images of New Zealand’s underwater world. Ian has a great gallery of nudibranchs photographed in New Zealand waters.
An educational site full of stunning underwater photographs, videography and leading marine biology reports and presentations. There are tools for students, teachers and all those interested in the New Zealand marine environment.
Wade Doak’s Website
The Diver’s Discussion Forum has fish observations, mainly from the Poor Knights Islands, but also other New Zealand sites. A great resource to find out what interesting things people are seeing and where. Also a good site on which to post pictures of unfamiliar species where they can be identified by experts.