There are over 50 species of abalone worldwide - three of which are found in New Zealand.
New Zealand species include yellow foot pāua (Haliotis australis), white foot pāua (Haliotis virginea) and black foot pāua (Haliotis iris). Black foot pāua are endemic to New Zealand and the largest of the three species. They are the main variety to be commercially harvested in New Zealand.
Haliotis Iris takes its name from the Rainbow Goddess of Greek Legend, Iris, owing to its brilliant multicoloured, iridescent shell. Blackfoot pāua falls under the species category of edible sea snails, a marine gastropod mollusc in the abalone family. It is most commonly found in shallow, cool waters, at depths less than six metres. The species occurs all around mainland New Zealand, Stewart Island and the Chatham Islands.
Black foot pāua.
Endemic to NZ
Yellow foot pāua. Commonly called "Queen pāua"
Whitefoot pāua. Smaller and rarer abalone species
Blackfoot pāua, Haliotis iris, is the most brightly coloured of New Zealand’s seashells. Its outer oval shell is rough and dull coloured – often encrusted with seaweeds and other marine organisms.
Inside, the shell is a mix of beautiful iridescent blue, green and purple hues. It's colouring is a biological phenomenon that mimics the physics in a rainbow. The shell structure is made up of microscopic crystal layers that refract light which causes the apparent bright colours - similar to that of a butterfly wing or peacock feather. Pāua also has true colour within the shell due to trace amounts of different minerals.
Beneath the shell is a shiny, black, muscular foot which enables the pāua to glide about quite quickly when foraging for food.
Pāua reach sexual maturity, at about 80-90mm length, in three to four years. After that, growth slows as energy is switched from growth to reproduction. Larger pāua may be 25 years old or more. Adult black foot pāua range in size, reaching 150mm-180mm in suitable conditions. The record size is thought to be 205mm. A fully mature adult pāua weighs up to a kilogram in weight.
The Minimum Legal Size (MLS) for harvesting pāua around New Zealand is 125mm, apart from along the Taranaki coast, where the MLS is 85mm. Professional pāua divers voluntarily opt to collect larger-sized pāua to ensure a good spawning population is left in place.
Pāua are herbivores, feeding on algae, seaweeds and kelp species. Pāua eat by partially lifting themselves off their rock to capture pieces of drift seaweed. Pāua will also move small distances to tackled attached kelps and seaweeds nearby.
A rough, belt-like tongue called a radula, which has thousands of tiny teeth, removes small pieces of seaweed to be digested. They prefer soft, fleshy, higher protein species of red and brown seaweeds and use their tongues to scrape microscopic algae off rock surfaces. The type of algae consumed seems to have some bearing on pāua’s shell colour.
Pāua are mostly motionless during the day. They live in a range of reef habitats, under rocks and ledges in intertidal and subtidal areas, and also in aggregations in exposed areas. Adult pāua live in depths up to 15 metres, though most occupy the area between the low tide mark and six metres. Pāua often aggregate on shallow reefs. When disturbed, they cling to the rock with their powerful muscular foot.
Habitats range from as far as the Three Kings Islands in the north, to the Chatham Islands in the far east, to Stewart Island and Fiodland in the deep south where pāua are particularly abundant owing to the cooler waters and abundance of seaweeds.
Pāua have a pair of eyes, a mouth and breathe through gills. The holes in a pāua’s shell are used for respiration, sanitation and reproduction. They continue to be formed throughout the life of the pāua. Like other abalone species, pāua are permanently attached to their shell. The shell begins forming in the larval stage and provides protection from predators. The foot of pāua is housed inside the shell. It is a broad and flat strong muscle used for attaching pāua to its environment and for moving around.
The strength of the foot make pāua exceptionally difficult to remove. An epipodium – a ruffle of tissue with sensory tentacles – is found along the edge of the foot. Pāua’s digestive, respiratory, circulatory and reproductive organs are in a circle surrounding the foot, whereas pāua’s head and mouth are located near the most recently formed hole on the shell.
Male and female pāua are broadcast spawners. This means they release many thousands of gametes (sperm and eggs) into the water through the holes in their shells. Fertilisation occurs in the ocean. The fertilised eggs hatch into microscopic larvae which float around for about a week, then settle on the bottom of the ocean where they start to develop shells.
Survival rates of pāua are very low due to predation and unsuitable habitats for juveniles to settle and grow.
Pāua’s main natural predators include crabs, rock lobster, octopuses, reef fish and starfish – who cover pāua’s breathing holes, forcing it to detach from the rock it was clinging to. Juvenile larvae are particularly vulnerable, which is why they tend to live in "cryptic" habitats in early life stages. Over-harvesting, damage caused by inappropriate fishing tools, pollution and climate change, are all factors that can also adversely affect pāua populations.
A VULNERABLE SPECIES
Pāua are a highly valued fish. The per kilo price for pāua meat can be substantial. Therefore, they make a profitable fish to catch and sell. Sadly, like other abalone species, the strong market for pāua makes it a species vulnerable to illegal fishing. Their population attributes and biology also work against them in respect to poaching and heavy fishing efforts:
Pāua live in aggregations, making them easier to find and harvest en masse
They are sedentary animals so cannot escape or shift even when fished
Pāua reproduction is very localised. Once fishers find a subpopulation, they tend to fish in that same location until there are no pāua left. Fishers then move on to the next patch setting up a cycle of serial depletion - a well recognised risk for abalone populations. Once aggregations of adults are depleted, reproduction becomes less and less successful as there are fewer adults in close proximity to reproduce with one other
Pāua are vulnerable to damage, even if they are returned to the sea. This is partly due to their lack of a 'clothing' mechanism meaning they bleed out easily if cut while being removed.