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Growth models, age frequency and size frequency distributions of sea urchin populations (Heliocidaris erythrogramma) in native macroalgal beds and sea urchin barrens
Growth models were constructed for two sea urchin populations over a two-year period using a tag-recapture study in the Mercury Passage, Tasmania. Sea urchins were tagged using tetracycline and calcein and growth models constructed using measurements taken from sea urchin jaws.
Underwater visual census surveys were conducted at 15 sites in eastern Tasmania to quantify the abundance of the sea urchin Heliocidaris erythrogramma and several putative predators.
Sea urchin tagged using tetracycline display visible marks in jaw elements and test plates that can be used to determine growth and subsequently an individuals age. Natural growth lines in the same structures can be used to determine age if natural lines are deposited at a consistent rates independent of age. Sea urchins were tagged using tetracycline and age determined from both fitted growth models and the number of bands deposited. Rates of natural line deposition were also quantified.
Estimates of abalone (Haliotis rubra) size at emergence within the Maria Island Marine Reserve and the Mercury Passage
Estimates of blacklip abalone (Haliotis rubra) size at emergence were obtained from surveys of ten sites within the Mercury Passage on Tasmania's east coast. Size at emergence estimates were obtained from five populations inside the Maria Island Marine Reserve (MIMR) and at five adjacent sites where abalone harvesting occurs. The data sets includes abundance and size estimates of the main abalone predators, including the southern rock lobster (Jasus edwardsii), and competitors.
Estimates of Blacklip Abalone (Haliotis rubra) mortality rates attributed to Southern Rock Lobster (Jasus edwardsii)
Predation mortality rates of blacklip abalone (Haliotis rubra) were estimated under several different conditions using a range of manipulative experiments. Abalone mortality rates were estimated from tethering experiments inside the Maria Island Marine Reserve (MIMR) and at an adjacent site where predators, including southern rocks lobster (Jasus edwardsii) were in low abundance, due to fishing. Estimates of abalone mortality directly attributed to rock lobsters were gained from manipulative experiments inside the MIMR and in an aquarium experiment at the Tasmanian Aquaculture and Fisheries Institute facility at the Marine Research Laboratories.
The movement and behaviour of the Southern Rock Lobster (Jasus edwardsii) was monitored using a radio acoustic telemetry systems at two sites in eastern Tasmania.
Mortality rates of the sea urchin Heliocidaris erythrogramma where estimated under experimental conditions to determine the importance of natural and predation mortality in structuring sea urchin populations. Data was obtained from tethering, tagging and caging experiments at four sites within Mercury Passage and the Derwent Estuary in eastern Tasmania.