Long Spined Sea Urchin

Centrostephanus rogersi

In Australia the long spined sea urchin is endemic to the warm temperate waters of NSW. It has been estimated that as much as 50% of the near shore reef area in NSW has been converted to barren habitat by urchin grazing.

Over recent decades, the distribution of the long spined sea urchin has extended southwards from southern NSW, through Victoria and Bass Strait and down the east coast of Tasmania. In some areas, abundance has increased, and the species has established sufficient densities to form destructive grazing aggregations, removing the overstory macroalgae that is an essential component of a healthy reef ecosystem.

The expansion has been climate driven with the extension of the Eastern Australian Current. The waters adjacent to southeast Australia, including Tasmania are considered an ocean warming hot spot and are experiencing an annual mean ocean temperature of four times the global average. The historically cooler waters of eastern Tasmania are now regularly above the temperature threshold for  larval development, enabling viable populations of the long spined sea urchin to be established.

Once established, urchins form “barrens”, areas of reef that are denuded of vegetation. These are referred to as “incipient barrens”. If left unchecked they can develop into “extensive barrens” that are large areas of bare reef that are difficult and expensive to reverse.

 Barrens are now established from the Bay of Fires in the state’s Northeast to Cape Pillar in the far Southeast. Given the broad distribution of the species and environmental conditions expected to facilitate ongoing populations, it is generally accepted that eradication of the long spined sea urchin is not achievable. There is however scope to prevent incipient barrens becoming extensive barrens.

There are five identified management options for the remediation of incipient barrens: -

  • Direct cull by abalone and commercial divers during fishing activities.
  • Direct control by dedicated culling.
  • Direct control by development of an urchin fishery
  • Direct control by using high calcium quicklime to kill urchins
  • Indirect control by enhancement of predators

The Tasmanian Rock Lobster Fishermen’s Association have been involved in the enhancement of predators option since 2013. To aid in the prevention of extensive barren formation the TRLFA have participated in the following  two initiatives: -

  • Improving the biomass of rock lobsters on the east coast – Rock lobsters are a known predator of urchins. IMAS have advised that the most efficient way the rock lobster fishery can aid in the prevention of barren extension is to increase the stocks of rock lobster.  In 2013 the TRLFA supported the State Government 10-year plan to restrict catches of rock lobsters on the east coast. The harvest strategy is designed to rebuild stocks to a minimum level of 20% of an unfished stock by 2023. The historically high commercial catch of 418 tonnes (2005/6) on the east coast has been reduced by over 60% to 131 tonnes. In 2013 the estimated biomass in parts of the east coast was as low as 8% of an unfished stock. IMAS stock assessment data for the last two years indicates that stocks are steadily rebuilding, with significant increases in the southeast. The increase is expected to improve markedly over the next 5 years for all parts of the east coast.

 

  • Translocation – The capture of slow growing deep-water lobsters from the SW and release into specified sites on the east coast. With funding from the State Government, the TRLFA have managed the capture and release of more than 145,000 lobsters to areas identified as fast growth areas. The initial project was for a three year period, completed in 2017/18. The State Government has now announced funding for a further four year period. This will see the translocation of a further 30.000 lobsters this year (2018/19). The initiative is specifically designed to improve stocks generally and help prevent the expansion of barrens.

 

Indicative map of east coast translocation release sites







 
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