This thesis describes the ecology and impact of the introduced European basket clam, Corbula gibba (Olivi, 1792), in Port Phillip Bay, Victoria. A bay-wide survey conducted in 1998 found C. gibba throughout the bay but it was significantly more abundant in deeper, muddier sites. Life history studies carried out at three sites found that two sites were dominated by a single cohort of large adults while the third site had one cohort of adults and one of juveniles. This juvenile cohort grew at a rate of about 4 mm2 per month but experienced high mortality, with only 0.5% surviving a six month period. Longer term abundance patterns available at St. Leonards, and supplemented by this study, found that, between 1969 and 1999, adult density varied between 0 and 106 individuals per m2 while juveniles were found in varying densities in 5 of 6 years sampled. The effect of anthropogenic disturbance on resident populations and subsequent invasion by C. gibba into disturbed sites was assessed experimentally using scallop dredging. Scallop dredging did not affect resident populations but the impact on subsequent invasion by C. gibba could not be determined as recruitment failed to occur over the study period and adult migration was not observed. The effect of ambient densities of C. gibba on endemic species such as the commercial scallop, Pecten fumatus, was investigated experimentally in the field. These experiments found that C. gibba significantly reduced the size and growth of juvenile P. fumatus to a greater extent than an equivalent number of conspecific scallops. Competition for shared food resources did not appear to be the mechanism underlying this impact, however, as dietary studies found that C. gibba was not a superior competitor. Additional studies found that C. gibba did not affect the recruitment of the native bivalves, Mytilus edulis and Electroma Georgiana, but significantly reduced conspecific recruitment. This effect is likely to have implications for the structure of C.gibba populations in the bay.

The study draws on the results of the studies described in metadata records (e3196ef0-e33c-11dc-97b4-00188b4c0af8 and 9c793960-e5af-11dc-a14a-00188b4c0af8) to demonstrate some of the effects of the loss of seagrasses to the total ecosystem. The area of meadows of the three dominant seagrass species in Princess Royal Harbour in 1960 was compared to the area in 1998.

To examine ecological interactions between fish and invertebrates, to aid in the understanding of potential impact through human disturbance.

Exclusions were attached to artificial substrata to investigate the relative effects of predation on the development of epifaunal communities at Portsea. Exclusions were black plastic mesh cages enclosing panels that were attached to rigs under the Portsea Pier. Bare control panels and cage controls where included in the experimental design. Cage controls had the bottom and half of the roof on the cage removed. There were 2 replicate panels of each treatment that were immersed for 2, 4 or 7 months and there were 6 runs of the experiment from October 1975 to November 1977. At the conclusion of each run of the experiment the panels were fixed in 4% formalin-seawater solution. In the laboratory, the number of individuals and percent cover of colonial species on each panel were recorded. Surveys identified that grazing fish were the most abundant predator of the epifaunal community at Portsea during the experiment. Predation significantly affected the pattern of establishment of the epifaunal community. There were fewer ascidian recruits and more diverse communities on bare control panels because fish predation prevented monopolisation of space by dominant ascidian competitors. On caged panels were there was no fish grazing, the survival of colonial ascidians was greater and the panels were dominated by arborescent bryozoans and ascidians.

Field surveys undertaken between 2006 and 2009 have been compiled to provide an extensive baseline of the distribution and abundance of rock lobster species from the Muiron Islands in the north to Turtles sanctuary in the south of Ningaloo Marine Park. The abundance of lobsters of all species were low, however there were regions that held significantly higher abundances of lobsters. The geographic regions and habitats types in which lobsters were found varied with lobster species.

The Ningaloo Marine Park (State Waters) Plan 1989 was designated A class in 1990. A review of the Management Plan began in 2000; this resulted in a revised Management Plan being approved by the Minister in January 2005. Changes in the current Management Plan include extending the Marine Park southwards to incorporate the full extent of the reef, increasing the number and extent of Sanctuary Zones, introducing Special Purpose Benthic Protection and shore-based line fishing zones. The purpose of this project is to provide what will become the first data point in a long-term data set. These data will become an integral part of several sections of the NRP, including not only assessing the ecosystem effects of fishing, but also in terms of evaluating the effectiveness of zoning for biodiversity conservation, and for assessing the implications of zoning for fish populations and for fishing outside sanctuary zones. The surveys will provide data not only for newly established zones, but also for those zones already established within the park under previous zoning provisions. Where possible the survey will build on existing data sets, though these are limited in scope and spatial extent. Objectives - For fish taxa targeted by anglers (e.g. labridae, lethrinidae, lutjanidae, serranidae, carangidae), - Measure the distribution, abundance and size-structure of key fish populations at Ningaloo - Provide data that will allow a quantitative comparison of these parameters to be made across Ningaloo Marine Park zones (pre-2005 sanctuary zones, new sanctuary zones, benthic protection zones, recreational zones and general use zones). - Provide data that will form the basis for being able to: Measure the rate and magnitude of any changes in fish population size or structure related to changes in marine park zoning - Determine how responses of fish populations may vary with respect to factors such as size of reserve, type of reserve, distance from boundary and fish life-history - Parameterize and test spatially-explicit models of fish populations.

Baseline data collection from 1990's to present

From 2006 to 2007 at northern Ningaloo Reef, stereo Baited Remote Underwater Video (stereo-BRUVs) and stereo Diver Operated Video (stereo-DOVs) were used to measure fish assemblages across shallow coral reef lagoon habitats. Four areas were identified including Osprey and Mandu Sanctuary, and Osprey and Mandu Reference Areas which were studied with stereo-BRUV and stereo DOV transects, during two successive summer and winter periods. Each time, six stereo BRUVs and 5 stereo-DOV transects were collected from within 6 coral reef lagoon habitats at 2 well established sanctuary zones and adjacent areas. The video footage was used to create the raw abundance and length data of different fish species.