Climate, Urchins, Barrens, Culls - Where to next?
NCMG Report on Federal Senate Inquiry into climate related invasive marine species & National Centrostephanus Workshop Launceston 1st and 2nd of Feb 2023
James Caffery and I were very fortunate in receiving an invitation to be part of the recent National Centrostephanus (Long Spine Purple Sea Urchin) workshop and would like to thank all the NCMG members for their support, which ultimately helped us get to the workshop in Tasmania. This event served to consolidate a breadth of knowledge on this issue and to provide a much clearer picture of the management strategies needed to address the challenges to be faced in the future.
National awareness around the issue of Urchin Barrens on the East Coast of Australia has been raised by the recent Federal Government Senate inquiry into the climate impact on invasive marine species. The Senate inquiry has sought submissions from a wide range of stakeholders and has held the first of three public hearings in Hobart already, with hearings scheduled for Victoria and NSW in the next few months. Nature Coast Marine Group, in collaboration with The Nature Conservation Council of NSW, The National Parks Association and Coastwatchers has made a submission to the inquiry and expect to be invited to the NSW hearing in due course. The Federal Senate committee aims to present its findings in a report by June 2023.
The Workshop held in Launceston in February was similar in many ways to the Narooma Symposium held in 2021, in inviting a broad range of stakeholders and scientists to present their views and provide thoughts on addressing the issue of Urchin Barrens. There were presentations from Indigenous Fishers from NSW, Industry reps and Scientists from all three states as well as international guests from both the East and West Coasts of U.S, New Zealand, Japan and Queensland who spoke about Urchin Barrens overseas and other invasive marine species such as Lion Fish and Crown of thorns starfish whose impact has been intensified by climate change.
These presentations served to reinforce understanding that the phenomena of Urchin Barrens is created by an imbalance in ecosystems due to a trophic cascade event, starting with the loss of apex predators and overfishing of competitive species such as Abalone. Once a tipping point is reached, urchins dominate the system and unless actively reduced in numbers by human intervention, reefs take a very long time to recover and in many cases are unable to re-establish without assistance.
Leading the scientific analysis and providing presentations on this issue in Tasmania, were Scott Ling and John Keane from IMAS. Both Scott and John provided detailed assessments and data showing results from studies associated with harvesting/culling programs conducted in Tasmania in collaboration with the Sea Urchin and Abalone Industries. Key findings were that the efforts needed to balance urchin numbers and restore reef health, varied depending on reef topography (e.g. bouldered vs flat reef) location (remoteness) and the existence of natural predators (Groper and Lobsters) in any given reef location. In other studies by Scott Ling around Lord Howe Island, he identified that several different species of Wrasse with sizes greater than 300mm in length were effective at balancing Urchins numbers. This finding is of particular significance when considering the situation of barrens in NSW and the historical fishing and spearfishing pressure put on fish such as Blue Groper (member of the Wrasse family).
Professor Adriana Verges from UNSW
Professor Adriana Verges from UNSW, Industry Reps and Citizen Science programs, demonstrated how in Victoria and NSW, overall reef health can be restored when Urchin numbers in both incipient and established urchin barrens are reduced.
Robert Chewying from the sth coast of NSW representing the sth coast indigenous fishing rights group presented to the workshop on an indigenous perspective on how Urchin Barrens have impacted on cultural fishing practices. Robert spoke about the importance of caring for Sea Country and how aboriginal fishers rotated catch of certain species of shellfish and the way middens keep a record of a group’s activity to provide a guide as to what species should be targeted or rested. In the structuring of subsidies for Urchin fishing in Tasmania, a similar approach has been found to be effective. Like indigenous fishers operated through history, rotational efforts to cull or harvest urchins more or less intensively in modern times is showing good results in Tasmanian waters for both reef health and the Sea Urchin fishery there
Scientists from Auckland University gave evidence on the migration of Centro Urchins range shifting further into NZ waters, with Centro Urchins now establishing barrens despite having fairly healthy populations of Snapper and Lobster, key predators of urchins. Other studies showed how establishment of Marine Parks was able to reverse urchin barrens in NZ, although it must be acknowledged that these barrens were formed by a different species (NZ Kina) not the Centros.
More studies are needed to identify the role of several key predators in these ecosystems and in particular, the time required for them to reach full maturity. The Eastern Rock Lobster Sagmariasus Verreauxi when fully grown attains a weight of 15kg as does Snapper Pagrus Auratus and can live as long as 40 to 60 years of age. Blue Groper Achoerodus Viridis can live as long as 80 years of age and grow to 1.2m in length. Other key studies need to be carried out to identify the competitive nature of shellfish such as Abalone and Turban Shells that share habitat with Centro Urchins.
The role of citizen scientists in addressing the spread of overly abundant species similar to Centro Urchins in Tasmania, was highlighted in a presentation by Ally Candelmo from REEF. In her presentation Ally showed the effects Lion Fish were having on reef ecosystems on the east coast of the U.S due to rising temperatures sending hotter water further Nth from the Gulf of Mexico. A voracious predator, Lion fish are decimating other smaller fish species key to keeping reefs in balance and they are moving further north out of their normal range. Communities have held spearfishing events where local fishers come together with chefs and media reps to raise awareness of the issue, in an attempt to control some of the numbers of Lion Fish migrating north.
In another example of citizen science playing a key role, Keith Rootsaert from Monterey Bay in California presented on programs there where amateur dive groups doing controlled culling at night, are rehabilitating reefs and in particular giant kelp forests. A key natural predator identified in this ecosystem is the California Sea Otter. Hunted for its pelt in the 1700 s, numbers of these animals were significantly reduced. Fortunately for the sea otters in Monterey Bay, habitat has been restored in some areas so successfully that they are considering re-homing some of these Otters due to their over-abundance in Monterey Bay. The tipping point that has been attributed to the reverting of this ecosystem to a barren state, is a marine heat wave event that affected a species of starfish that are a natural predator to the Urchins that caused a decline in the starfish’s numbers. Another key factor in Monterey Bay was the existence of a once lucrative Abalone industry operating around the turn of the 20th century. Many 1000s tons of Abalone were harvested while it was in operation and the wild Abalone fishery there has since collapsed.
The link between Abalone and Urchin Barrens was again identified in a presentation by Japanese Urchin Ranchers at the event seeking to expand potential ranching opportunities in Australia with Centro Urchins. In the 1950s and 1960s Japan exported up to 2000 tons of Abalone to China each year; now exports have reduced to less than 100 tonne a year. Urchin Ranching in Japan has become an alternative to Abalone fishing with ranching operations working in conjunction with seaweed farming to create an urchin food supply that is a closed loop in its nature. The process in Japan sees wild urchins that are low in roe content harvested from barrens and then then transferred to pens where they are fed the seaweed “meal “. Once adequately fed and containing healthy roe content, they are harvested. In Australia, early trials with Centro Urchins have shown that this is not an economically viable option. The Centro Urchins while being very large and robust in size (the largest in size in the world) are very sensitive to disturbances. Trials have shown that once removed from their original location they die easily therefore making them unsuitable for ranching operations.
We hope that, as a result of this conference of world experts, and the indisputable evidence that urgent action is required, some solid financial investment from both Federal and State governments will hopefully be allocated to address this issue. There was a clear acknowledgment from all attending the conference that there was more than enough scientific evidence to support the expansion of programs and projects all along the eastern range of the Great Southern Reef to manage Centro Urchin numbers. Further studies are of course needed to monitor closely the effects of Urchin fishery operations, the role of natural predators and the effects of climate change on the temporal range of Centro’s. For all the poor outcomes we are experiencing in our environment, our ability to reverse the effects of Urchin Barrens is very achievable with immediate action to put the right processes put into place.