Seaweek – What lies beneath?

Department of Conservation —  08/03/2020

Did you know New Zealand/Aotearoa is bigger than it looks? About 93% of it is actually underwater! Our total area goes 200 nautical miles out to sea from our coastline and 80% of our native species live in the ocean.

That is probably why we have a special affiliation with the sea.

Most Kiwis live near the coast, and a lucky few live in relative isolation on offshore islands. Nowhere is this more prevalent that in our only national park of the sea, Hauraki Gulf Marine Park/Ko te Pātaka kai o Tīkapa Moana. The Auckland region alone has 3,200 km of coastline, two thirds of which provides public access to the sea, while people live on Gulf Islands including Aotea/Great Barrier, Kawau, Rakino, Waiheke, Mercury islands and more.

Sunset view from Aotea/ Great Barrier Island.
📷: DOC

It’s an ideal way to celebrate Seaweek – Kaupapa Moana, New Zealand’s annual national week celebrating the sea. From Saturday 29 February to Sunday 8 March 2020, the NZ Association for Environmental Education (NZAEE) is highlighting the diverse connections and interactions we have with the sea which makes our lives so intertwined with the health and wellbeing of our ocean environment.

So, what lies beneath and why should we care? The answer is simple: the life-giving force of Tīkapa Moana provides for a richness and variety of species found nowhere else on this planet, from tiny rhodoliths that roll like tumbleweeds along the seafloor to 24m long Pygmy blue whales – and everything in between.

Did you know that the Marine Park is a nursery for multiple species of shark including great whites, threshers and hammerheads? Check out this video of hundreds of sharks, including many juveniles, swimming in the shallow waters of Aotea/Great Barrier Island, taken in January.

Great White photographed in our Marine Park.
📷: DOC

As well as great white sharks, two of the largest fish in the world, whale sharks and giant manta rays, visit to feed on the Gulf’s bounty. Other stingrays such as eagle rays are a food source for the iconic orca/ika kākahi, who often visit the Gulf in their close-knit family groups.

Orca family visiting the Gulf.
📷: Auckland Whale and Dolphin Safari

Speaking of big, the Hauraki Gulf Marine Park has a semi-resident population of about 140 Bryde’s (pronounced “brooders”) whales. Feeding on enormous quantities of plankton and small baitfish (pilchards and anchovies), these 15 m baleen whales are a sign of the abundance of life in the Gulf.

Bryde’s Whale spotted by the Auckland Whale and Dolphin Safari crew.
📷: Auckland Whale and Dolphin Safari

Super pods (up to 1,000!) of common dolphins/aihe hunt in Tīkapa Moana, herding huge schools of fish to the surface, providing fair game for seabirds such as gannets/takapū who dive into the sea at speeds of 145km/h with their eyes wide open!

Common dolphin super pod!
📷: Auckland Whale and Dolphin Safari

But it’s not all about the big guys. The diverse coastal and marine habitats of the inner and outer Hauraki Gulf are home to a multitude of fish/ika, shellfish, sponges, algae and more.  Underwater, the landscape is diverse as it is on land, with forests of kelp, sponge gardens and rocky reefs to name a few.

Ask any fisherman, and they will tell you that snapper is the king of all fish in the Gulf. Armed with sharp teeth, it’s not hard to see why. They consume a wide variety of foods found on rocky reefs, switching prey as they grow. Larger snapper are able to tackle heavily armoured shellfish and can even crack open prickly kina! This helps reduce the presence of kina barrens (areas where kina have eaten too much), which is why we need to only take what we need, allowing these large predators to keep kina populations in check.

Kahawai can travel at speeds of 100mph, while tarakihi can live to be wise old fish at 45 years old.

The powerhouse for all this life comes from single-celled algae called phytoplankton which uses the sun’s rays to produce energy, and in turn feeds animal plankton, known as zooplankton. Colourful sponges and colonial sea squirts which live permanently attached to rock surfaces in the Gulf, feed on this planktonic food as it drifts past them in the currents.

Plankton also provides food for two types of shellfish common in the Gulf, scallops and mussels. Mussels are a critical species for the Hauraki Gulf, as they are filter feeders that can filter out small particles including toxins from the water. A recent decision by the Hauraki Gulf Forum to restore 1000 sq km of mussel beds in the Marine Park will go a long way to help restore the health and wellbeing/mauri of the Park. And nerd-alert, a little-known fact is that scallops have two rows of eyes which can sense danger!

Let’s finish on kelp. Why? Because it too is an algae, and algae is the base for almost all marine life. So when you next see giant kelp, known also as bladder kelp, swaying in the currents of Tīkapa Moana, you can marvel at more than just the fact that it grows up to half a metre per day.

Help us celebrate the 20th birthday of Hauraki Gulf Marine Park/Ko te Pātaka kai o Tīkapa Moana by respectfully enjoying your big blue backyard.

You can:

  • keep rubbish away from streams that flow into the Gulf
  • wash your car on the lawn to stop chemicals from your brake pads ending up in the storm water drains that lead to Gulf
  • say no to single-use plastic – use a keep cup for your coffee and multi-use bottle for your water
  • if you are walking on the beach with your dog, keep it away from the marine species that come ashore to rest
  • if you see any rubbish on the beach, at the park or on the street, pick it up and dispose of it properly.

Love it, restore it, protect it.

One response to Seaweek – What lies beneath?


    Love your blogs; keep them coming.