The Piopiotahi Marine Reserve is situated along the northern side of Milford Sound, stretching from the village of Milford Sound to Dale Point, where it meets the Tasman Sea.
Milford is the northern most fiord of a World Heritage-listed area, shaped by powerful glaciers in times long past. While called Milford Sound Milford Fiord would be a more accurate description.
The reserve’s name, Piopiotahi, means “one native thrush”, a ground feeding bird, now thought to be extinct.
Piopiotahi was established in 1993, spans 16 km in length and covers an area of 690 hectares. The fiord consists mostly of steep rock walls with rocky shallow reefs in between. In the more inner fiord it reaches depths of over 400 metres deep, and towards the entrance, a maximum depth of 125 metres.
Delicate invertebrates cover steep rock walls on the inner side of the reserve - a thriving environment for black coral trees, tubeworms, sponges, soft corals, red coral, colonial sea squirts and anemones.
On the Tasman Sea side of the reserve deepwater species meet pelagic and reef species, which creates a great abundance in unique life forms to observe. Here divers are often greeted by spiny dog sharks, hundreds of rock lobster, octopus, numerous reef fish, schools of butterfly perch, stingrays, seals and even an occasional bottlenose dolphin encounter. Ancient brachiopods can also be found, which are clam-like animals that have remained unchanged for 300 million years.
This unique habitat is thanks to the huge amount of rain the area receives. The Fiordland area receives about 7 metres of rainfall per year. Numerous rivers, streams and thundering waterfalls pour a layer of tannin-stained freshwater into the fiords, which remains on the surface and can range from a couple of centimetres to about 10 metres deep.
Because this layer is stained to a tea colour, it reduces the amount of light able to penetrate into the depths, therefore tricking deepwater species into shallower waters. This phenomenon is also known as “deep water emergence”.
For example, black coral normally inhabit depths between 200m and 1000metres, where in Milford Sound they grow in depths of 8 metres and beyond which makes for a unique diver's paradise.