There are two types of sea urchins in Tasmanian waters, the
short spined sea urchin,
Heliocidaris erythrogramma which is endemic to Tasmania and has well established markets, and the long spined sea
urchin Centrostephanus rodgersii. The long spined urchin has become established in Tasmanian waters following changes to the East Australian Current which has allowed this invasive species to be transported from New South Wales to the east coast of Tasmania.
In the commercial fishery, there is no size nor catch limit for
Centrostephanus but for
Heliocidaris there is a total allowable catch of 175 tonnes and a size limit of 70 mm (diameter of test or shell inside the spines).
Short Spined Sea Urchin Fishery
Short spined sea urchin
The short spined sea urchin
has shorter, solid spines. They have a number of colour variations all made up of purple, green and/or white which often differ between the spines and the teste (shell).
The short spined sea urchin is the preferred species taken by commercial divers as the roe is highly prized particularly by Asian markets. However, the short spined urchin only produces about 5 per cent to 6 per cent of its body weight as roe which is about half the amount of roe produced by the introduced long spined urchins. Markets pay well for the short spined delicacy at a beach price of around $50-$60/kg.
In recent years, the fishery has taken more than 100 tonnes live weight annually. The short spined urchin commercial fishing season is generally from late July until February after which time spawning leaves the quality and quantity of roe uneconomically viable.
While the short spined urchin may form barrens, the extent of their development is far less intrusive than those formed by the invasive long spined urchins.
Long Spined Sea Urchin Fishery
Long spined sea urchin
The long spined sea urchin has spines longer than half its shell diameter. This urchin is dark brown to black with a turquoise-like sheen on the spines with red down their centre. However colours can vary.
The long spined sea urchin is a threat to Tasmanian ecosystems as it feeds on the marine algae leaving large barren areas on the sea floor and depriving abalone, rock lobster and other species of their feed and habitat. The impact on Tasmanian fisheries is a serious concern.
Initially it was thought that there were no viable markets for the long spined sea urchin as the rose was deemed unpalatable. However, over recent years changes in processing methods and further exploration of potential markets has seen the urchin devlop into a valued commodity. In 2018-2019 560 tonnes were harvested.
Besides the market for human consumption, markets are also being explored to use Centrostephanus in fertilisers and for fish bait, both of which are looking quite promising. The Centrostephanus can produce in excess of 10 per cent of their body weight in roe and is generally harvested from around January through to July.