Will a native predator help to control novel, range-extending urchins on temperate reefs in Tasmania?

In Tasmania, a global climate change hotspot, the continued expansion of the Longspined Sea Urchin (Centrostephanus rodgersii) is one of the biggest challenges facing marine scientists and fisheries. As the urchin population shifts southwards in response to warming waters, valuable and diversity-sustaining kelp habitat is rapidly destroyed, leading to the desertification of underwater landscapes. The resulting urchin barrens are unable to support populations of commercial fishery species such as abalone and rock lobster and the transformation to barren can see the loss of up to 150 native species. The Southern Rock Lobster (Jasus edwardsii) has long been lauded as a potential predatory control mechanism for these urchins on the East Coast of Tasmania. However, with the conversion rate of reef to barren increasing at around 10% a year, it is critical we review the efficacy of current control methods. We investigated lobster diet in the wild using multiple diet analysis techniques: stomach contents analysis, DNA testing of faecal samples, and stable isotope analysis. We compare these results to findings from captive feeding trials to discuss prey preference in Southern Rock Lobsters. We found that although the Longspined Sea Urchin does contribute to the diet of lobsters in some instances, native prey items are consumed at a higher rate in both wild and captive lobsters. These results suggest the need to employ other control strategies if we are to stem the expansion of the Longspined Sea Urchin in Tasmania.