Moana Uta (Wet Jacket Arm) Marine Reserve: Protected Marine Landscapes in Fiordland, New Zealand

The fiord itself carries a long human story. European exploration of Wet Jacket Arm is generally traced to 1773, when the crew of HMS Resolution under Captain James Cook charted and named the inlet. The name 'Wet Jacket Arm' comes from an incident in which crewmen rowed the length of the fiord in calm conditions, only to be caught by a sudden storm that left them without a fire for warmth or cooking, and thus spent the night in damp clothes. The name has stuck ever since.

In the early twentieth century, the wider Fiordland region became the unlikely home of introduced moose. Moose brought from Canada were released in Fiordland in 1910 and photographed intermittently over subsequent decades. A photograph purportedly taken in Wet Jacket Arm in 1953 was later shown to have been captured in a different location, illustrating how the remote and visually uniform character of Fiordland's fiords has historically confused even well-intentioned observers. 'Moose hunting' trips continued into the later twentieth century, although the animals have since disappeared from the landscape.

The marine reserve itself was the product of a more recent, deliberate conservation effort. In 2002, the Fiordland Marine Guardians launched a strategy to protect the area's marine environment, which they presented to Minister for the Environment Marian Hobbs and Minister of Fisheries Pete Hodgson in 2003. Following this advocacy, Wet Jacket Arm was officially designated as a marine reserve on 21 April 2005, giving statutory protection to its waters from Entry Island to the head of the sound.

Since its establishment, the reserve has continued to benefit from inter-agency management. The Department of Conservation administers the site, while the Ministry of Primary Industries, the Fiordland Marine Guardians, and other agencies collaborate to monitor the marine environment and to prevent the spread of invasive seaweed. In 2021, the New Zealand Air Force conducted aerial surveillance flights over the reserve and adjacent waters to detect illegal commercial fishing activity.

Wet Jacket Arm is a classic Fiordland fiord: a long, narrow, steep-walled inlet carved deep into the mountains of the South Island's southwestern coast. The reserve covers the full length of this inlet, from Entry Island near its mouth to the far head of the sound. Towering forested slopes rise on either side of the water, and the cliffs often drop abruptly toward the surface without the gradual shelving that characterises most coastlines.

Within the reserve, the underwater landscape is equally diverse. The shoreline includes extensive rock walls and broken rocky reef, while the central basin plunges to considerable depth and is fully shielded from ocean swell. Smaller estuarine inlets branch off the main sound, and islands such as Oke Island punctuate the waterway, each with their own distinctive tidal conditions. These varied substrates and exposures create an unusually compact range of marine microhabitats within a single fiord system.

The freshwater cap on the surface is one of the most distinctive physical features of the reserve. In some places this layer is merely a thin film of a few centimetres; in deeper basins influenced by higher rainfall it can extend to around ten metres below the surface. Beneath this lid, the marine water is calm and clear, a striking contrast to the rough, swell-driven coastal environment outside the fiord.

The reserve's ecosystems are shaped as much by water column structure as by the surrounding land. The interplay between freshwater runoff from the heavily forested catchments, marine water entering from the outer coast, and tannins leached from the temperate rainforest produce a stratified environment unlike almost anywhere else in New Zealand.

In the upper marine layer, where light penetrates and the water is warm and stable, extensive communities of sponges and corals thrive alongside reef fish. Rock walls near points of stronger tidal flow, such as around Oke Island, support suspension feeders such as lampshells (brachiopods), which depend on moving water to deliver their food. Below the tidal zone, some rocky reefs host dense kelp beds and sea urchins (kina).

The deep central basin is dominated by black coral colonies, which establish themselves in low-light, low-disturbance conditions. Brittle stars live among the branches of these coral colonies, taking advantage of the structure they provide. Deeper still, tannin-stained water limits the ability of most marine life to persist, creating a quiet and impoverished but visually dramatic lower layer that descends hundreds of metres toward the seabed.

Moana Uta supports a mix of marine and coastal wildlife drawn from the broader Fiordland ecosystem. Bottlenose dolphins (aihe) are known to use the fiord's sheltered waters, and New Zealand fur seals (kekono) haul out on the surrounding coast and islands, taking advantage of the rocky terrain. The reserve also provides habitat for two penguin species: the Fiordland crested penguin (tawaki), a species strongly associated with the Fiordland coast, and the smaller little blue penguin (kororā).

Underwater, the most celebrated wildlife feature is the dense population of black coral in the deep basin, where their branching structures host brittle stars and other invertebrates. Brachiopods, or lampshells, are locally common along exposed rock walls and represent one of the more unusual and ancient lineages of marine life still present in Fiordland. Together, these species give the reserve a distinctive wildlife profile that reflects both the unusual water conditions and the undisturbed nature of the fiord environment.

The reserve's principal conservation value lies in its protection of one of Fiordland's most ecologically distinctive fiords. By prohibiting fishing, the taking or moving of marine life, and anchoring in many areas, the reserve preserves an environment where fragile communities such as black coral forests, sponge gardens, and lampshell colonies can persist with minimal direct human interference.

Its placement within the broader Fiordland Marine Guardians' conservation framework reflects a coordinated view that the region's fiords are exceptional and require targeted protection. The reserve also plays a role in controlling invasive marine threats: agencies including the Department of Conservation, the Ministry of Primary Industries, and the Fiordland Marine Guardians work together to monitor and prevent the spread of invasive seaweed in and around the reserve.

Enforcement is an active element of management. Aerial patrols by the New Zealand Air Force in 2021, for example, were used to detect illegal commercial fishing activity in the reserve and nearby waters. The reserve's regulatory regime also recognises the cultural responsibilities of Ngāi Tahu, allowing authorised collection of pounamu and certain marine mammal remains in ways that respect customary protocols while preserving the broader ecological protections of the site.

The reserve's dual name reflects the shared cultural landscape of Fiordland. 'Moana Uta' is the name used by mana whenua, particularly Ngāi Tahu, recognising the long-standing customary relationship of Māori with these waters and their resources. The English name 'Wet Jacket Arm' originates from Captain James Cook's 1773 voyage aboard HMS Resolution and reflects the European exploration history of the fiord.

The reserve's regulations accommodate Ngāi Tahu cultural practices alongside ecological protection. Authorised customary collection of pounamu (greenstone) is permitted, as is the collection, under appropriate protocols, of deceased marine mammals and certain of their remains. These provisions reflect recognition of the role of tangata whenua as kaitiaki, or guardians, of the marine environment and acknowledge that the fiord has long cultural as well as ecological significance.

Moana Uta (Wet Jacket Arm) Marine Reserve stretches across an entire long, narrow Fiordland fiord, offering an unusually complete snapshot of how these southern inlets function. Among its most distinctive features are the highest known densities of black coral in Fiordland, thriving in a shaded, sheltered basin beneath a stable freshwater cap.

The reserve also stands out for its diverse microhabitats: tidal rock walls with lampshells and other suspension feeders, kelp beds and kina on shallow reef, steep rock walls, deep basins, and estuarine pockets. Its recognition of Ngāi Tahu customary rights, including authorised pounamu collection, adds a cultural dimension that complements its ecological protection.

Fiordland's climate is famously wet, with substantial rainfall feeding the freshwater layer that defines Wet Jacket Arm's water column. Calm, settled weather offers the best conditions for appreciating the fiord's quiet grandeur and for diving or snorkelling, when the marine visibility in the upper layers is at its clearest. Cooler months may bring stronger storms and reduced access, while the brighter summer months generally provide longer daylight hours and more favourable boating conditions.

Wildlife sightings are not strongly seasonal in this sheltered environment, though penguin and fur seal viewing tends to be easier along accessible rocky shorelines throughout the warmer months. Because the reserve is in a remote part of the South Island, visitors should expect weather to play a defining role in any trip, with the calmest conditions typically aligning with the broader New Zealand summer.