Rejuvenating the ocean one urchin at a time

•  Divers Greg Forsyth and Shane Blackwell with a daily catch of Longspined Sea Urchins off the East Coast. 

By Taylor Clyne
August 03, 2022

One local diver is working to return balance to the marine ecosystem while providing a high-end delicacy across the globe. 

Shane Blackwell spends most of his week underwater along the East-Coast, Eddystone Point, St Helens, and as far south as the Tasman Peninsula, collecting Longspined Sea Urchins for predominately Asian markets. 

Blackwell and divers like him are turning a pest into a profitable commodity harvesting hundreds of tonnes each year for their gonads, which are edible. 

The former Winnaleah resident said the devastating impacts of urchins can be seen daily across the ocean beds, but commercial intervention is seeing positive impacts. 

“The urchin basically eats everything leaving huge barrens on the ocean beds which cause massive issues to the kelp forests and diverse eco system,” he said. 

“Under the water you need kelp and sea grass for other animals to survive, namely abalone and rock lobsters, but the urchins over graze and leave bare shiny rock losing the healthy eco system.” 

When barrens occur more than 150 species are lost to urchin invasion. 

“There are incentives from the government to dive in certain areas and I think in some areas we are getting on top of the issue, particularly from the 0-25metre mark,” Blackwell added. 

The challenge, however, is that natural kelp recovery effectively requires the removal of almost every urchin from a given area to give it a fighting chance. 

Research Fellow Dr John Keane for the Institute for Marine and Antarctic Studies (IMAS) said the Longspined Sea Urchin is basically the poster child for climate change having first been discovered on the East Coast in 1978. 

“The presence in Tasmanian is a result of warming waters along the East Coast. 

“The urchin is native to New South Wales after being brought to Australia originally from overseas; it spawns in winter with its larvae only surviving when the water is warmer than 12 degrees,” he said. 

“Tasmania’s average winter ocean temperature has increased from 11 degrees almost 13 degrees, so it’s pushed above the threshold meaning its larvae can float down the East Australian Current, settle and survive, which is what we are seeing.” 

Going back fifty years this simply didn’t happen. 

IMAS conducts research to understand urchin ecology and impacts which includes surveying urchin populations and barren extent, trials of control measures such as culling and enhanced predation (by dropping rock lobsters), assessment of the wild harvest fishery and increasing its profitability. 

In 2020 urchin invasion was a concern on Babel Island off the East Coast of Flinders Island the government funded a ‘take all harvest’. 

“Divers were paid by the government to remove all the urchins to give the ocean beds a chance at replenishing, and to protect valuable abalone stocks. 

“As extensive sea urchin barrens, like what they saw on Babel Island, have severe negative impacts on abalone and rock lobster populations, diminishing the associated recreational and commercial fisheries.

“Since March the harvest of urchins has been permitted in the Elephant Rock Fisheries Research Area at St Helens as well and in under four months 97 tonnes have been harvested and processed for global markets,” Dr Keane said. 

“This is some great work by our North-East divers.” 

A typical catch day for Shane Blackwell is between 700-800kg per dive however his largest catch in one day tipped the scales at 1740kg. 

“It’s all driven by the processor and what they want,” Blackwell added. 

The main processing factory is based in Hobart, employing over 60 people and processing up to five tonnes of urchins per day. 

The commercial season starts at the end of December until end of July each year with the ultra-premium A grade urchin row fetching a price of up to $400 per kg in retail markets. 

“We will continue studies on this creature and the fishery, and hope to keep the urchin spread to a manageable level in Tasmanian waters,” Dr Keane said.

“Of all the control measures, a viable commercial urchin fishery is proving to be the one having the most impact.

“In the last five years over 2,000 tonnes have been harvested, with the majority coming from the North-East coast. 

“There have been some positive outcomes in and around St Helens where kelp is regrowing, and native species returning,” he concluded.