By Roger Grace

The Department of Conservation (DoC) has recently released a discussion document on a proposal for a large marine reserve on the remote northeast coast of Great Barrier Island. It is an ambitious project, but has the potential to become one of the greatest marine conservation successes in New Zealand. A real treasure for future generations.

At 56,000ha, it would be by far the biggest marine reserve close to the New Zealand mainland, dwarfing the first marine reserve at Leigh (518ha), and even the large Te Tapuwae O Rongokoko marine reserve (2452ha) north of Gisborne. But the proposed Great Barrier Island marine reserve would still be less than eight percent of the size of the ginormous Kermadec Islands marine reserve (748,000ha).

Most marine reserves around the New Zealand coast are quite small. In fact recent research is showing that bigger reserves would be far more beneficial for some of the more mobile species. Even quite small marine reserves, however, can have really positive effects on aspects of the marine ecology and biodiversity. Small specialised marine reserves in certain areas are fine, but we need large ones too, to get an effective network of these ‘marine national parks’.

If we are to get anywhere close to the 10% target for marine protection by 2010 as the Government wants, then we will have to start thinking BIG. This proposal certainly qualifies in that respect.

The area that DoC is looking at for a marine reserve extends from the Needles at the north end of Great Barrier to Korotiti Bay, about half way down the east coast, and eastward to the 12-mile limit of the territorial sea. The area encompasses the widest range of marine habitats available around the island. Together with already protected land habitats, the new marine reserve would provide fully protected status from the mountain tops to the edge of the continental shelf. Ecological corridors would be protected throughout this full range.

The wide variety of marine habitats is one of the key factors of particular value in this proposed reserve, as protection of the full range of marine habitats is part of the Biodiversity Strategy 2000, the Government policy document driving the push for more marine reserves. Here no fewer than eight major marine ecological types are present, each with its own special physical characteristics, and each with its own special make-up of marine life.

In the middle of the coast is Whangapoua Estuary, which is recognised as the most undisturbed estuary in northern New Zealand. It has high value as a habitat for several rare and endangered bird species (New Zealand dotterel, variable oystercatcher) and supports about a third of the total population of the endemic brown teal. The Department of Conservation also recognises that the estuary is the best source of cockles and pipis for people on the island, and is keen to listen to the people’s needs.

The open coast is sheltered from southwest winds but exposed to the northeast. It includes the surf beach of Whangapoua, and a more sheltered beach at Harataonga, a popular camp ground and snorkelling area. Wild rocky shores with pebbly coves characterise the northern coast, while more sheltered rocky shores drop quickly on to sandy sediments south of the estuary.

Offshore Rakitu Island is an imposing sight with its stark white cliffs and plunging shores. Sheltered on the western side, the outer coast is rugged with rocky headlands and reefs dropping to maximum diving depths. A delightful sheltered cove is a popular anchorage at the northern end of the island, and diving is superb around the entrance to the cove.

Further offshore there is a maze of rocky reefs, pinnacles and boulder fields. At 75 to 110 metres depth, they are beyond conventional scuba diving, but provide an unusual habitat for some of the richest assemblages of rocky bottom animals known in New Zealand. The high parts of the reefs, which stick up 20 to 30 metres above the surrounding seabed, are bristling with black coral trees up to three metres tall, many with coatings of fluorescent pink jewel anemones adorning dead branches. There is also a second, peach-coloured species of black coral.

Rare glass sponges, usually found in much deeper water, occur commonly on the high reefs where the constant gentle currents keep the reefs free of silt yet supply abundant plankton for food. Giant tube sponges nearly a metre tall, large fan-like sponges, and strange gorgonian fans are scattered amongst a living fuzz of small encrusting bryozoans, hydroids, colonial seasquirts and cup corals.

Underwater video revealed subtropical Lord Howe Island coralfish and foxfish, but we did not see any hapuku although the habitat looks right. The reefs have been heavily fished for hapuku for years, some black coral showing broken branches with bits of fishing line wrapped around the stumps.

Sediment areas between Rakitu Island and the mainland support a mosaic of communities of animals living in the sand. With increasing depth the sediment becomes muddy. Out on the continental shelf deep water tusk shells and some strange small fan shells can be found in the mud out to nearly 150 metres depth.

The northeast side of Great Barrier Island is one of the last places where divers can occasionally see old giant packhorse crayfish, which once were common throughout the Bay of Plenty and Northland east coast. Smaller marine reserves have developed high numbers of large red crayfish, but have done nothing to assist recovery of packhorse. It is hoped that protection of this large area may allow packhorse numbers to climb back, and perhaps one day we will again see many huge packhorse in shallow water like in the old days.

There is no doubt that with full protection the marine life of this area will thrive. Snapper and red crayfish numbers and sizes will increase many times as they have in the marine reserve at Leigh. The reserve may also be large enough to allow schooling fish such as kahawai, kingfish and trevally to form spectacular schools again. There could be many surprises as we have no marine reserve even close to this size near the mainland to guide us as to what could happen. Large hapuku back in shallow water?

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