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Fiords

by  Paddy Ryan

New Zealand’s fiords, in the south-west of the South Island, are unique. They are spectacular to look at – and they are host to a dazzling variety of animal life. Their waters are so dark that creatures which usually live only in the deep ocean can survive there, giving scientists a peephole into little-explored territory.


A unique environment

Remote and rugged, the inner reaches of the 14 fiords (also spelt fjords) of south-west New Zealand are unique. Fiordland’s climate, vegetation and topography have combined with oceanic influences to create habitats and biological communities that have no counterpart anywhere in the world.

Glacial origin

The fiords were carved out of the mountains by massive glaciers some 20,000 years ago. When the glaciers melted, vast quantities of rocky debris were left at the entrance of each fiord. These mounds formed a partial barrier when the sea level rose 6,500 years ago, and today they restrict the flow of sea water in and out of the fiords. Within each fiord, the circulation of water is confined to the top 20–40 metres; deeper waters may remain undisturbed for years.

Damp and dark

Fiordland is one of the wettest places in New Zealand: over 7.5 metres of rain falls on this precipitous landscape every year. Huge volumes of water, discoloured after passing through native forest and layers of rotting leaf litter, flow down into the fiords. This yellowy brown fresh water forms a layer above the sea water that fills the fiords, and reduces light levels, allowing only greenish light to penetrate.

Narrow band of life

Steep sides and a thick layer of fresh water restrict most life in the fiords to a narrow band around rock walls down to just 40 metres below the surface. The habitable area is only about 46 square kilometres; much smaller than the harbours at Manukau (370 km²) or Wellington (77 km²).

Deep-water species

It is this reduced level of light that makes the fiord waters so special. Green light is not very effective for photosynthesis and consequently there is only limited seaweed growth on the walls of the fiords. With less competition for space from seaweeds, encrusting and sessile animals like sponges and corals flourish on the underwater walls.

Near Fiordland, the continental shelf falls away sharply and a number of deep-water animals are carried from the Tasman Sea into the dark sheltered waters of the fiords. Here, conditions are similar to those of the deep ocean, and species such as black corals, sea pens and lampshells thrive on underwater cliff walls. Scientists label the phenomenon of animals surviving at depths much shallower than their normal range ‘deep water emergence’.


Underwater rock walls and basins

Upper zone: surface down to 15 metres

Most marine organisms in the fiords live on the rock walls. In depths to 5 metres, the upper layer of fresh water restricts communities to those capable of living in a brackish environment. The zone is impoverished, dominated by green seaweed (Ulva species), mussels, barnacles (Eliminius species), shrimps (Palaemon affinis) and the small cushion star Patiriella regularis.

Below the layer of fresh water the communities are extremely diverse. Between depths of 5 and 15 metres the rock walls are encrusted with tube worms, sponges, soft corals, sea squirts and molluscs. These are food for a variety of starfish, urchins, sea snails and sea slugs. In normal circumstances the big 11-armed starfish Coscinasterias calamaria assembles in large numbers just below the fresh-water layer. When several days without rain causes the layer to recede, the starfish have access to the mussel band, and feasting begins.

Underwater observatory

It is possible to view some of Fiordland’s marine life without getting your feet wet. The Milford Deep Underwater Observatory allows visitors to descend 10.4 metres below the surface to view black corals, red corals and other marine life. The marine animals are held in special trays that are raised in the morning and lowered to depths more congenial to their occupants at the end of the day.

Lower zone: 15–40 metres deep

In the perpetual gloom of depths from 15 to 40 metres, large sponges, sea squirts, corals, hydrocorals and lampshells (brachiopods) dominate the rock walls. Black coral, usually confined to offshore islands at depths greater than 45 metres, grows in abundance in all the fiords, in colonies that are up to 5 metres tall. Underwater, the colonies are a ghostly white – it is the skeleton that is black and gives the coral its name.

A small (7.5-centimetre) white sea cucumber (Ocnus species) is common on underwater cliff faces. In a few places in Fiordland the strawberry sea cucumber Ocnus brevidentis dominates the zone just below the fresh-water layer.

Lampshells are common throughout most of Fiordland. In some areas it is estimated that they reach densities of 1,000 per square metre.

The glass sponge Symplectella rowei is found at depths of 30–50 metres, attached to submarine cliff walls in Doubtful Sound. They are the largest sponges in Fiordland, and an example of deep water emergence; glass sponges are usually found only in deep oceans or the polar regions.

Deep basins: more than 40 metres

Below 40 metres, and down to the bottom of the fiord basins (up to 450 metres), animal life is more sparse. Heart urchins and tube worms predominate to depths of 200 metres; below this, shellfish, heart urchins and crabs live in a muddy environment similar to that at depths of 1,000 metres in the open ocean.


Fish and marine mammals

Fish

Over 150 species of fish are known from New Zealand’s fiords. The fish life there is distinctive. One species, the brotula Fiordichthys slartibartfasti, lives only in Fiordland. Except in Doubtful Sound and Milford Sound, where amateur fishing is commonplace, blue cod (Parapercis colias) are so tame that they will swim up to divers. Girdled wrasses (Notolabrus cinctus) may nip the exposed parts of divers – typically their lips. Butterfly perch (Caesioperca lepidoptera), first collected on James Cook’s second voyage to Dusky Sound in 1773, tend to follow divers for a while before losing interest. Such behaviour may lead to a mistaken impression that there is an abundance of fish.

A novel name

The scientific name given to a new species is often taken from the person who discovered it. However, in the case of the brotula fish, Fiordichthys slartibartfasti, scientists had a bit of a laugh. The name doubly celebrates the fiords where these fish live. Fiordicthys means fish of the fiords, and Slartibartfast was a character who designed fiords in Douglas Adams’s 1979 comic novel The hitchhiker’s guide to the galaxy.

Jock Stewart fish (Helicolenus percoides) and scorpion fish (Scorpaena papillosa) tend to sit on the bottom of the fiords or, in the case of scorpion fish, occasionally in trees of black coral. Scorpion fish are well camouflaged, but Jock Stewart fish are easy to see because of their large reflective eyes.

Common triplefin or cockabullies (Forsterygion lapillum) abound, and in the middle and inner fiords they may be found in densities of hundreds per square metre.

The only deep-water fish known to live in the fiords is the elegant wavyline perch (Lepidoperca tasmanica). They normally live around rocky reefs at 150–400 metres, but in the southern fiords they can be found at depths of 6–31 metres.

Marine mammals

New Zealand fur seals (Arctocephalus forsteri) are common in the fiords. They breed on offshore islands near fiord entrances, and when juveniles disperse from their colonies it is often to the inner fiords.

Unusually, there is a resident pod of about 60 bottlenose dolphins (Tursiops truncata) in Doubtful Sound. They have been intensively studied, and their seasonal pattern of movement between the Doubtful, Thompson and Bradshaw sounds is well known. Other marine mammals such as elephant seals, leopard seals, orcas and the occasional larger whale are also irregular visitors to the fiords.


Conservation

Piecemeal management

The environmental management of New Zealand’s fiords was hindered by the absence of a single co-ordinating agency. Fiordland’s terrestrial environment is protected under the National Parks Act 1980; however, its jurisdiction stops short of the water, at the high-tide mark. The marine ecosystem is excluded from both Fiordland National Park and the Southwest New Zealand Te Waipounamu World Heritage Area.

Two small marine reserves were established in Fiordland in 1993 in an attempt to protect the animals within them. These were the Te Awaatu Channel (The Gut) Marine Reserve in Doubtful Sound, and Piopiotahi in Milford Sound.

Environmental threats

There has been regular commercial fishing in the fiords for over 50 years. The main species which are targeted are blue cod, crayfish and pāua (abalone). Other fisheries have been proposed for sea cucumbers and sea urchins.

The greatest threat to the fiords comes from increasing accessibility and tourism. In 2005, about a third of all overseas tourists to New Zealand visited Fiordland. A boom in recreational fishing and diving has brought an increase in destruction from curio hunters, anchors, moorings, craypots, and sewage disposal. The impact of individual eco-tourism activities is low; however, their cumulative effect is significant.

Guardianship

Because there was no other management body, the Guardians of Fiordland Fisheries and Marine Environment was formed in 1995. The group is made up of representatives of tangata whenua, the fishing industry and charter operators. They have identified a number of management issues and made wide-ranging and practical recommendations. Of special note is their recognition of areas of high biodiversity that need special protection.

Bulls in china shops

Small discrete areas with fragile animal communities were likened to china shops by the Fiordland Guardians. The group realised that even dropping a heavy anchor into one of these areas could cause irreparable damage. They considered themselves the bulls that must be kept out of the china shops.

Acknowledging the need for conserving representative areas, the Guardians proposed making the whole of Sutherland Sound a marine reserve. In response, the New Zealand government passed the Fiordland Marine Management Act 2005, which ensured that 928,000 hectares were set aside as a special management area, and created eight new marine reserves. With the continued support of government and an increasing public awareness of conservation issues, there is a good chance that the fiords will remain a rich and unique environment.


Hononga, rauemi nō waho

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How to cite this page: Paddy Ryan, 'Fiords', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/fiords/print (accessed 15 November 2019)

Story by Paddy Ryan, published 12 Jun 2006