Tuhua (Mayor Island)

Tuhua (Mayor Island) Marine Reserve protects 10.6 square kilometres of coastal waters surrounding the northern and north-western shores of Tuhua, a dormant volcanic island lying about 35 kilometres off the coast of Tauranga in the Bay of Plenty region. ^[1] Established in 1992 and managed by the Department of Conservation, the reserve safeguards clear, subtropically influenced waters around an island of national geological and cultural importance. Tuhua is renowned as a source of obsidian (volcanic glass), prized by Maori, and its surrounding reefs, drop-offs and kelp forests host a mix of temperate and warm-water marine species. ^[2] The reserve is a notable diving destination, valued for its water clarity and abundant marine life.

The reserve's waters host a diverse mix of temperate and warm-temperate reef fish, including snapper, blue maomao, demoiselles, red moki, leatherjacket, butterfish and large schools of trevally and kingfish that visit the offshore reefs. ^[1] Its position offshore in the warm East Auckland Current brings occasional subtropical visitors not common on the mainland coast. Crayfish and reef invertebrates such as kina, sponges and anemones are abundant on the rocky reefs and drop-offs. New Zealand fur seals haul out on the island and forage in the surrounding waters, while seabirds including shearwaters, petrels and gannets feed offshore, and dolphins and migrating whales are sometimes seen passing the island.

Underwater, the reserve supports kelp forests and rich algal communities adapted to the relatively warm, clear offshore waters. Bladder kelp and other large brown algae form canopies over the rocky reefs, while bull kelp fringes exposed edges and ecklonia kelp covers many subtidal surfaces. A varied understorey of red, green and brown seaweeds, including coralline turf and encrusting algae, blankets the reef. These marine plants provide food and shelter for grazing invertebrates and juvenile fish, and the comparatively warm waters around Tuhua allow some species more typical of northern New Zealand to thrive at the southern edge of their range.

Tuhua is a rhyolitic volcanic island, one of the most significant in New Zealand, formed by eruptions that produced lava domes, ash and extensive deposits of obsidian, the black volcanic glass for which the island is famous. ^[1] The island contains two summit crater lakes — Lake Aroarotamahine (Green Lake) and Lake Te Paritu (Black Lake) — and steep, rugged terrain; its highest point, Opuahau, reaches 354 metres. ^[1] The volcanic origins of the island extend offshore into the marine reserve. The surrounding seafloor combines rocky reefs and boulder slopes of volcanic rock with deeper sandy areas, and underwater drop-offs reflect the island's steep volcanic flanks. This volcanic geology, including exposures of obsidian and rhyolite, gives the reserve a distinctive seabed structure prized by divers, and geothermal activity produces underwater hot springs in parts of the reserve.

The reserve enjoys a mild, subtropically influenced maritime climate, warmed by the East Auckland Current that flows down the eastern Bay of Plenty. Summers are warm and humid, while winters are mild, and sea temperatures range from around 14-15 degrees Celsius in winter to 20-22 degrees Celsius in late summer, among the warmest reef-diving waters on New Zealand's mainland coast. The offshore island is exposed to swells and winds from the open ocean, and conditions can change quickly. Settled summer weather typically brings excellent water clarity, while strong winds and ocean swells can make the 35-kilometre crossing and diving access challenging.

Tuhua has profound significance for Maori, especially the iwi of the western Bay of Plenty, and the island's obsidian was a highly valued resource traded throughout New Zealand for cutting tools and weapons — archaeological evidence shows obsidian from Tuhua distributed across sites from Tiwai Point to the Kermadec Islands. ^[1] The island was occupied and used for fishing, gardening and resource gathering, with pa sites and archaeological remains attesting to long settlement. Tuhua remains under the kaitiakitanga (guardianship) of Te Whanau a Tauwhao ki Tuhua, and access to the island is managed by the Tuhua Trust Board in partnership with iwi. ^[2] The surrounding waters were and remain important fishing grounds, and the cultural value of both the island and its marine environment underpins the protection of the reserve.

Tuhua (Mayor Island) Marine Reserve was established in 1992 under the Marine Reserves Act 1971 to protect a representative example of offshore, subtropically influenced reef habitat and to complement the conservation values of the island itself. ^[1] Covering the northern portion of the island's coastline, the reserve was created with the involvement of the island's traditional owners and the Department of Conservation, recognising both the ecological and cultural importance of Tuhua's waters. Since its establishment it has been managed as a no-take area, allowing marine populations to flourish and providing a benchmark for the recovery of fish and invertebrate communities in offshore Bay of Plenty waters.

The reserve's principal attractions are its diving and snorkelling sites, regarded as among the best in the Bay of Plenty for water clarity and marine life, with Orongatea Bay offering accessible shallow rock platforms for snorkelling. ^[1] Divers explore volcanic reefs, drop-offs and kelp forests teeming with reef fish, crayfish and colourful invertebrates, with the warm offshore waters occasionally hosting subtropical species. On the island itself, walking tracks lead to the summit crater lakes and lookouts over the volcanic landscape, offering a memorable land-based complement to the marine experience. Boat-based wildlife watching for seals, seabirds and dolphins, and the island's striking obsidian geology, add to its appeal for visitors making the offshore journey.

Access to the reserve is by boat across roughly 35 kilometres of open sea from Tauranga, the nearest city, typically via charter or private vessel; the crossing requires settled weather. ^[1] There are no visitor facilities within the marine reserve. The island is privately owned by Te Whanau a Tauwhao ki Tuhua and managed by the Tuhua Trust Board; visitors must arrange access with the Trust Board in advance and follow quarantine procedures on arrival. ^[2] Diving, snorkelling and fishing charters operate seasonally from Tauranga and surrounding harbours. Visitors should plan carefully for the exposed crossing and changeable ocean conditions, and remember that all fishing and collecting are strictly prohibited within the reserve.

As a no-take marine reserve, Tuhua prohibits all fishing, shellfish gathering and removal of marine life, allowing fish and invertebrate populations to recover and helping to safeguard a representative offshore ecosystem. ^[1] The reserve is managed by the Department of Conservation in partnership with the island's traditional owners, reflecting both ecological and cultural conservation goals. Monitoring tracks the abundance of reef fish, crayfish and other species within the protected area. Conservation priorities include maintaining the island's predator-managed status to protect seabirds — native species including kiwi, kaka and North Island robin have been reintroduced — alongside guarding against marine pests and climate-driven changes in the warm offshore waters, and ensuring the reserve's no-take rules are respected by those visiting the remote site.