A management support framework for subtidal rocky-reef communities on the east coast of Tasmania
Marzloff, MP and Johnson, CR and Little, LR and Frusher, SD and Ling, SD and Soulie, JC, A management support framework for subtidal rocky-reef communities on the east coast of Tasmania, MODSIM2011, 19th International Congress on Modelling and Simulation, 12-16 December 2011, Perth, Australia, pp. 2142-2148. ISBN 978 0 9872143 1 7 (2011) [Refereed Conference Paper]
We developed a local and regional scale simulation model of the important dynamical features
of seaweed-based rocky reef systems in eastern Tasmania. Climate-driven range extension of the spiny sea
urchin (Centrostephanus rodgersii) from Australia’s mainland into eastern Tasmanian waters presents a
major threat to the productivity of subtidal rocky-reef communities because overgrazing of native seaweed
beds by this sea urchin can create and maintain extensive areas of ‘barrens’ habitat. This causes major loss of
production, biodiversity and physical structure. In particular, the two most valuable fisheries in Tasmania,
blacklip abalone (Haliotis rubra) and southern rock lobster (Jasus edwardsii), are not commercially viable on
C. rodgersii barrens. Additionally, the fishing depletion of large rock lobsters, the main natural predator of C.
rodgersii, facilitates the establishment of urchin barrens.
Based upon empirical observations, field experiments and information about larval dispersal derived from an
ocean circulation model, we developed a model that captures the regional dynamics of temperate reef
communities on the East coast of Tasmania. Our model is hierarchically structured as a connected network of
local models, which can each produce ecosystem shifts from productive kelp bed to sea urchin barrens at the
scale of individual reefs. Connectivity between local reefs essentially captures large-scale dispersal of C.
rodgersii larvae. Through simulations, we test the effectiveness of alternative management options (reduction
in lobster fishing, temporary no-take zones as a series of ‘rolling closures’ and harvesting of the urchin) to
minimise the risk of serious ecological impacts of the invasive urchin, i.e. to maintain native reef
communities in their original state or restore the productive seaweed habitat from the barren state. Through
model forecasts, we assess the trade-off between alternative management strategies in terms of costs and
benefits for the fisheries and risks of further sea urchin barrens formation.
Refereed Conference Paper
ecosystem model, larval connectivity, ecosystem effects of fishing, sea urchin barren, southern rock lobster, temperate rocky-reef, management support tool.