Effect of Centrostephanus rodgersii barrens on standing stocks of abalone and rock-lobster in Tasmania

The effect of barrens formed by the long spined sea urchin, Centrostephanus rodgersii, on the standing stocks of southern rock lobsters (Jasus edwardsii) and black lip abalone (Haliotis rubra) was estimated by divers using underwater visual census methods to compare lobster and abalone abundance in barrens with that in adjacent kelp habitat. Abalone (H. rubra) and rock-lobster (J. edwardsii) populations were compared on C. rodgersii barrens and in adjacent algal-dominated habitat at the same depth and on the same substratum type at three sites in eastern Tasmania (Elephant Rock:Binalong Bay, St Helens Is, and Mistaken Cape:Maria Island). At Elephant Rock and St Helens Island , the barrens are extensive and well established Type 1 barrens, while at Mistaken Cape the barrens in 8-14 m are incipient Type 4 barrens, comprising small barren patches in the algal bed (see FRDC report for classification of barren types). Note that while there are extensive barrens in deeper water (>18 m) at Mistaken Cape, at these depths working time is limited and it was difficult to locate intact macroalgal beds on equivalent substrata.