Codfish Island / Whenua Hou: An Essential Nature Reserve and Protected Island Geography

The history of Codfish Island / Whenua Hou begins well before European contact. Archaeological investigations in 2007, led by Angela Middleton, Ian Smith, and Atholl Anderson, identified two distinct phases of human occupation. The earliest phase dates from approximately the 13th to 15th centuries, when Māori communities were active throughout New Zealand, leaving behind stone artefacts and middens containing fish, bird, and mammal bones. The second phase occurred during the 19th century, broadly from 1800 to 1830, in the era of European sealing and exploration.

In 1808 the island received the English name "Pegasus Island" from the whaler Eber Bunker, prompted by the landing of sealers and the beginnings of European habitation. Because of tensions caused by sealers on nearby Stewart Island and concerns over the treatment of local Māori women, the Ngāi Tahu rangatira Honekai designated Whenua Hou as the site of a protected mixed-race settlement. Under his authority, Europeans who had married or partnered with Māori women, including figures such as Thomas Chaseland, were encouraged to relocate to the island. This settlement at Sealers Bay became one of the first sustained mixed Māori and European communities in southern New Zealand, and the names "Codfish Island" and "Whenua Hou" were both in use by around 1824.

The modern conservation era began in 1987, when the first kākāpō were transferred to the island from Stewart Island. Following the eradication of possums and rats in 1998 and the later removal of weka, the island became a predator-free refuge and the central hub for kākāpō recovery. Since then, major breeding seasons in 2002, 2009, and 2016 have helped drive population growth for the species, and the Department of Conservation now uses Codfish Island / Whenua Hou as a principal site for ongoing native species management. The island remains closed to the general public, with access reserved for researchers, Department of Conservation staff, and authorized conservation volunteers working under permit.

Codfish Island / Whenua Hou is a compact island covering about 14 square kilometres, set in the open waters of the Tasman Sea west of Stewart Island. Its topography is shaped by its southern exposure and maritime climate, with a low-to-moderate relief that rises to a maximum elevation of around 250 metres near the south coast. From this central high ground, slopes descend into coastal forest, rocky shoreline, and sheltered bays such as Sealers Bay on the northeast of the island.

The island's vegetation is dominated by temperate coastal forest, which extends down to the shore in many places and creates a habitat mosaic that supports both forest-inhabiting birds and seabirds nesting along the coast. The remote position, steep terrain, and lack of permanent human settlement have preserved a relatively undisturbed natural landscape.

Ecologically, Codfish Island / Whenua Hou functions as a near-pristine predator-free refuge in the southern New Zealand archipelago. Because rats, possums, and weka have been removed, the island supports a community of birds, bats, and seabirds that would otherwise be highly vulnerable to introduced mammals. Forest habitats fill much of the interior, while coastal cliffs and rocky shorelines provide nesting opportunities for a wide range of seabird species.

The island sits within a broader regional ecosystem that includes Stewart Island / Rakiura and surrounding waters, and its biological character shares much with that larger landmass. However, the absence of predators and the focus on active species management have made its ecological communities unusually intact compared with much of the New Zealand mainland.

Codfish Island / Whenua Hou supports a remarkable concentration of New Zealand's most threatened native species. Among its most recognizable residents are kākā, fernbirds, red-fronted and yellow-crowned parakeets (kākāriki), Pacific black ducks, and a recently introduced population of mōhua. The island is also home to the southern short-tailed bat, one of New Zealand's few native terrestrial mammals and a species of significant conservation interest.

The island's seabird colonies are internationally recognized. BirdLife International has designated Whenua Hou as an Important Bird Area because of its importance as a breeding site for Fiordland penguins, yellow-eyed penguins, mottled petrels, Cook's petrels, and the Whenua Hou diving petrel. Conservation managers have also translocated Snares Island snipes to the island, expanding the range of this rare shorebird.

The most famous wildlife story associated with Whenua Hou, however, is that of the kākāpō. Roughly half of the global population of this critically endangered, flightless parrot resides on the island, and it has become the leading site for kākāpō recovery. The island's most famous individual is Sirocco, a male kākāpō born on Codfish Island in 1997, who was later named New Zealand government's Official Spokesbird for Conservation.

Codfish Island / Whenua Hou is regarded as one of the most important offshore conservation sites in New Zealand. Its status as a predator-free island, achieved through the eradication of rats, possums, and weka, makes it a critical refuge for species that have been heavily impacted by introduced mammals on the mainland. The island's importance is recognized internationally through its designation as an Important Bird Area by BirdLife International.

The island anchors the national recovery programme for the kākāpō, hosting the majority of the species' breeding population and acting as the operational centre for intensive monitoring and management. Major breeding events on the island in 2002, 2009, and 2016 produced some of the largest chick cohorts in kākāpō recovery history. The Department of Conservation also uses the island for related species management, including the introduction of Snares Island snipes and mōhua.

In addition to its ecological work, conservation management on Codfish Island / Whenua Hou incorporates the protection of its cultural and archaeological heritage. Earlier surveys identified sites of pre-European Māori settlement and items from the 19th-century mixed Māori and European community at Sealers Bay, ensuring that the island's historical significance is considered alongside its wildlife values.

Codfish Island / Whenua Hou holds deep significance in both Māori and early European colonial history of southern New Zealand. The Māori name "Whenua Hou," meaning "new land," reflects the island's role as a place where a new community was deliberately established. In the early 19th century, the Ngāi Tahu rangatira Honekai designated the island as a refuge for sealers who had taken Māori wives, in response to tensions over their presence on Stewart Island. This made Sealers Bay one of the earliest documented mixed Māori and European settlements in the region.

Archaeological work in 2007 revealed evidence of much older human activity, including stone artefacts and middens from Māori occupation during the 13th to 15th centuries. These findings indicate that Whenua Hou was part of broader Māori use of the southern islands long before European arrival. The dual Māori and English place name that is now official reflects the island's ongoing importance in the cultural landscape of Ngāi Tahu and in the wider history of southern New Zealand.

Codfish Island / Whenua Hou's standout qualities include its role as the centre of New Zealand's kākāpō recovery programme and its status as a predator-free island of national and international importance. The presence of homes for more than 70 kākāpō, including the famous Sirocco, gives the island a unique place in global wildlife conservation.

Equally notable are its recognized seabird colonies, which have earned the island Important Bird Area status, and its layered cultural history, spanning early Māori settlement and one of the first mixed Māori and European communities in southern New Zealand.

Codfish Island / Whenua Hou is closed to casual visitors and unauthorized landings, and there is no general public tourism season. Access is permitted only to authorized Department of Conservation staff, scientific researchers, and conservation volunteers, with arrivals typically by light aircraft or helicopter into Sealers Bay. For those involved in conservation or research visits, the most productive periods of activity tend to align with the summer months in the Southern Hemisphere, when seabird breeding, kākāpō monitoring, and significant fieldwork are concentrated.