Description of experimental markers and locations for east side of
Cape Schanck - reef code 13.01.

Project:   Understanding the ecological role of abalone in the reef ecosystem of Victoria Funded by: Fisheries Research and Development Corporation and Fisheries Victoria

Investigators:   Paul Hamer, Greg Jenkins, Harry Gorfine, Brent Womersley

Images:

• Experimental crevice/wall habitat that we will monitor for change in encrusting communities resulting from abalone depletion
• fixed site sub-surface float markers that are situated immediately adjacent to each experimental crevice/wall
• fixed photo-quadrat markers that are cemented to the experimental crevice/walls.

The success of the project depends on the markers remaining in position and that we have control over major changes in abalone numbers within the experimental crevice areas. We would therefore appreciate if the markers are not disturbed, and that abalone within the experimental crevices are not removed until we provide further advice.

The experimental areas on each crevice should be obvious from the cement markers fixed to each wall, see figure c).

If you happen to come across one of the experimental crevices and notice the cement markers (figure c) it would be helpful to us if you could make a mental note of the amount of fouling on the markers and if possible inform us of your observation.

b.  Site marker float adjacent to experimental crevice/wall)

c.  Photoquadrat markers AquaKneadIT with red plastic starplugs and tags) that are fixed to experimental crevice/walls

We greatly appreciate your co-operation with this research and will continue to keep you informed on our progress.

For further information please contact Paul Hamer at DPI, Queenscliff.

Ph. +61 3 52580288
Mobile 0409334395
Fax. +61 3 52580270
Email: paul.hamer@dpi.vic.gov.au

Understanding the Ecological role of Abalone
in the Reef Ecosystem of Victoria

There is very little known about how abalone influence, or are influenced, by other reef species. This project is aimed at investigating whether there are any interdependent relationships between abalone and other reef-associated species.

Knowledge of such relationships may allow identification of indicator species that can be incorporated into harvest management plans and local-scale fisheries assessments.
For example, anecdotal reports of changes in the appearance of reefs after serial depletion and the lack of recolonisation of such areas, even after fishing has ceased (i.e. non-recoverable reef), suggest that overfishing can result in changes to reef communities that alter the habitat suitability for abalone. An example of this would be a shift in domination of the reef substrate by pink encrusting coralline to sponge.

Abalone predominantly occur in crevices where encrusting coralline dominates, and this is the preferred juvenile settlement habitat, a shift to sponge domination of the substrate would severely impact on the habitat suitability for abalone. Questions such as 'How do abalone influence the persistence of encrusting coralline in crevice habitat?' are important to answer. Furthermore, knowledge of such interdependent relationships will allow assessment of the potential, and actions necessary, for rehabilitation of reef areas that once sustained viable abalone populations.

The outcomes of this project should not only satisfy the requirements of the Department of Environment and Heritage (DEH) under the Environment Protection and Biodiversity Conservation Act 1999 (i.e. management plans for fisheries such as abalone need to include information on ecosystem effects of fishing), but importantly should provide assurance to industry that harvest strategies can be designed with consideration of broader ecological impacts.

Research plan:

Because abalone are largely crevice dwellers the most likely ecological impact(s) of removing abalone would be on the biota associated with and immediately adjacent to crevices, in particular encrusting species that influence the suitability of the substrate as a habitat for abalone (eg. encrusting coralline algae, sponges, sea squirts). The first summer and winter sampling will involve baseline sampling of selected crevices at sites in each of the eastern (Mallacoota), central (Cape Schanck) and western zones (Portland/Port Fairy), and at least one MPA site. We will choose crevices that are large enough to carry out photoquadrat sampling and with varying densities of abalone (i.e. each crevice at least 1m opening and several metres long). We will measure various physical parameters of each crevice to include in the data analyses and look for relationships between abalone numbers in crevices, crevice structure, and the types and cover of encrusting species.

This period of baseline monitoring is critical for several reasons.

• Firstly, it will provide an opportunity to refine sampling methodology and selection of study sites.
• Secondly, it will provide data on patterns of variation that can be used to generate hypotheses on the effects of removal of abalone.
• Thirdly, it will provide two seasons of data for comparisons with removal experiments that will begin immediately after the winter 2007 baseline sampling.

A manipulation (removal) experiment has been strongly supported by the steering committee for this project as a necessary requirement to provide some clear conclusions as to ecological impact of abalone depletion. The removals will involve complete removal (with repetitive fishing to maintain low to zero density) of abalone from some of the crevices (impact), and no removal from others (controls). The removal and control sites will be monitored in summer and winter 2007 and 2008 to see what impact removal of abalone has on the crevice communities. The abalone removed from crevices may be translocated to other suitable nearby areas on the advice of the local industry (we do not envisage large numbers, probably several 100).
We prefer that the experimental sites are not fished during the experiment, this would involve at most 5 crevices (approximately 3-4 length meters each) in each zone. Experimental crevices will be marked and GPS co-ordinates, and sub-surface floats. Detail of experimental sites and markers will be provided to fishermen.

Another aim to this project is to understand the importance of fish predation on abalone, and whether or not any fish species are highly dependent on abalone for food? Tasmanian researchers are already looking at rock lobster predation of abalone. We have chosen to focus on the eastern zone during 2007 as we have a reliable source of fish samples (Paul Bozinis) and most of the fish species that occur along the Victorian coast can be found at various locations throughout this zone. Banded morwong are also most abundant in the eastern Victoria zone and are thought to be a predator of juvenile abalone. We will assess the role that abalone play in reef fish diets, and assess how predation by reef fish may influence abalone mortality rates.

For further information contact Paul Hamer

Primary Industries Research Victoria -
Marine and Freshwater Systems
P.O. Box 114, Queenscliff, Victoria, Australia, 3225
Ph. +61 3 52580288 Mobile 0409334395 Fax. +61 3 52580270
Email: paul.hamer@dpi.vic.gov.au