By overgrazing seaweeds and sessile invertebrates, essentially back to bare rock, the advent of the long‐spined sea urchin Centrostephanus rodgersii in eastern Tasmanian waters poses a significant threat to the integrity, productivity and biodiversity of shallow (<40 m) rocky reef systems and the
Budget expenditure: $828,551.00
Project Status:
Completed
Principal Investigator: Craig Johnson
Organisation: University of Tasmania (UTAS)
Project start/end date: 19 Apr 2008 - 30 Jun 2011
Contact:
FRDC
TAGS
Invasive Species
Habitat
SPECIES
Southern Rock Lobster
Blacklip Abalone
Sea Urchins

Need

There is clearly potential for C. rodgersii barrens to cover ~50% of nearshore reefs on the east coast of Tasmania, as is already the case in NSW and the Kent Group in Bass Strait. This would reduce both the Tasmanian abalone and rock lobster fisheries by ~15%, with a loss of value totalling ~$25M (before processing). The need for a management response is self evident.

Large rock lobsters (=135 mm CL) are the key predators of C. rodgersii in Tasmania, and experiments have shown clearly they can prevent sea urchin populations from building to the point where overgrazing occurs. There is urgent need to assess the viability of controlling C. rodgersii populations through changing current management of the rock lobster fishery, and through targeted removal by divers as a tactical response on small scales.

However, before management instruments are invoked in an attempt to minimise the risk of further development of barrens habitat or rehabilitate existing barrens, it is imperative to carefully evaluate the effectiveness of potential management strategies. The proposed research will provide the necessary information and knowledge base to enable robust management decisions.

The proposed work has strong support from managers and the fishing industry in Tasmania, is acknowledged as a high priority by the relevant RAGs, and addresses several high priorities on both the State and TAFI strategic research plans.

Objectives

1. To assess the effectiveness of translocating large rock lobsters (=135 mm CL) en masse as means of preventing formation of incipient barrens and rehabilitating incipient and extensive barrens.
2. To assess the effectiveness of a range of management options (e.g. imposing upper size limits and spatial management) in building the biomass of large (=135 mm CL) rock lobsters to levels sufficient to limit C. rodgersii populations.
3. To assess the effectiveness of killing or removing sea urchins by abalone divers during the conduct of their fishing activity, as a means of preventing formation of incipient barrens and rehabilitating incipient and extensive barrens.

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