Biosphere | Ecological Dynamics | Community Structure
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The impact of the introduced New Zealand screw shell, Maoricolpus roseus, were assessed using a cageing experiment in SE Tasmania (Bligh Point, D'Entrecasteaux Channel). Three treatments consisted of different substratum type (live, dead and empty shells, and dead shells with 50% occupancy by hermit crabs); which were crossed with 2 levels of screwshell density (high and low). Treatment groups were artificially maintained for 20 months before metabolic chambers were used to quantify the community metabolism of different treatment groups.
Management options to minimise formation of urchin barrens: measuring changes in marked incipient barren patches
A photographic and in situ diver survey of marked incipient Centrostephanus rodgersii barren patches, in eastern Tasmanian, was used to assess any changes in the grazed area and shape at experimental (lobster translocation/ research reserve protection sites; and abalone diver urchin cull sites) versus control sites.
Management options to minimise formation of urchin barrens: timed lobster swims - assessment of lobster size and abundance in south-eastern Tasmania
Characterisation of lobster (Jasus edwardsii) abundance and change in abundance at three different sampling sites (Cape Paul Lemanon, North Bay and Fortescue Bay) on the south-east coast of Tasmania, was assessed by GPS tracked SCUBA diver swims of 60 minutes in length whereby GPS was logged approximately every 5 seconds. Large tagged Rock Lobsters were introduced into one of the sampling sites, North Bay (which was closed to fishing). The swims are also being used to assess the impact of reef closure on the local lobster population.
Management options to minimise formation of urchin barrens: assessing dynamics of incipient urchin barrens patches in eastern Tasmania using timed swims
Timed GPS-tracked swims using SCUBA (45 and 30 minutes), were used to assess the changes in frequency and size of Centrostephanus rodgerii incipient barrens in eastern Tasmania. The number of C. rodgerii and Heliocidaris erythrogramma in each incipient barren were also assessed.
Quantitative assessment of direct and indirect impacts of introduced New Zealand screwshells (Maoricolpus roseus) on native soft sediment assemblages
We used an in situ manipulative experiment to assess the impacts of the introduced New Zealand screwshell, Maoricolpus roseus, on native soft-sediment community structure and habitat characteristics in SE Tasmania. Impacts were assessed for high and low screwshell density and for the effect of live and dead screwshells, as well as those containing hermit crabs.
Impacts of New Zealand screwshells (Maoricolpus roseus) on native scallop distribution and behaviour
The impact of the introduction of the New Zealand screwshell (Maoricolpus roseus) on scallop distribution and behaviour in the D'Entrecasteaux Channel, SE Tasmania was investigated. The impact of both live and dead and empty M. roseus shells on the distribution of two sympatric scallop species, queen scallop (Equichlamys bifrons) and doughboy scallop (Chlamys asperrimus) was quantified at large spatial scales. Also quantified was the impact of M. roseus on the distribution and behaviour of the commercial scallop (Pecten fumatus), at both large and small spatial scales.
Impacts of New Zealand screwshells (Maoricolpus roseus) on growth and condition of juvenile commercial scallops (Pecten fumatus)
The impact of the introduction of the New Zealand screwshell (Maoricolpus roseus) on growth, condition and survivorship of juvenile scallops (Pecten fumatus) at Bligh Point in the D'Entrecasteaux Channel, SE Tasmania was investigated. A manipulative experiment was used to quantity the impact associated with live and dead M. roseus shells and to quantify differences in interspecific and intraspecific competition.
Management options to minimise formation of urchin barrens: kelp lines - assessment of changes in kelp growth at the kelp-barren interface
Linear video transects (40m total length; 20m into barrens and 20m into kelp from original fixed marker on the benthos) were used to assess changes in kelp growth in several points along the kelp - urchin barren interface in north-east Tasmania (St. Helens Island, Sloop Rock and Elephant Rock research areas). The video transects were deployed in the same position, and assessed at different points of time. The video was analysed in the laboratory to assess percentage of kelp and barren cover, as well as the kind of substratum, kelp species identifiable and number of sea urchins (Centrostephanus rodgerii and Heliocidaris erythrogramma) and other benthic organisms when present (rock lobster and abalone).