Movement and re-aggregation of blacklip abalone in response to intensive fishing
Final report
Typically abalone are found clustered into aggregations of many individuals along gutters and ledges that dissect the surfaces of the reefs they inhabit. Commercial abalone divers take advantage of this clustering behaviour and specifically target aggregations to minimise the time spent searching for abalone and maximise their catch rates. This approach to abalone harvesting would be expected to progressively reduce the number and size of the aggregations to produce a less clustered pattern of distribution. Most methods used to detect changes in abalone abundance that result from fishing assume that abalone movement will have minimal effect on post-fishing patterns of distribution.
Abalone are generally viewed as relatively inactive organisms that occupy specific homesites from which they seldom move. Evidence for this lack of movement includes the oval shaped 'scars' of bare rock, free of algae and other immobile invertebrates, that remain after abalone are harvested. However there are many anecdotes describing the tendency for abalone to reform aggregations after fishing and during spawning periods. Presumably the latter promotes fertilisation success by increasing the quantities of sperm and eggs that mix in the water. It is unclear why abalone may aggregate into clusters outside spawning periods. If re-aggregation does occur after fishing, it is also unclear where these 'replacement' abalone come from. There is some speculation that small abalone may emerge from crevices and cryptic habitat. Other hypotheses include small-scale movements within aggregations or migration from unfished areas. An understanding of how re-aggregation occurs after fishing and to what extent it occurs, is essential to determine its effect on estimates of abalone abundance and to estimate important population characteristics such as rates of natural mortality.
Keywords: Haliotis rubra, abalone, dispersal, movement, aggregation, natural mortality, tag-loss, tag-recapture, stunted, growth.
People development program: FRDC Indigenous development scholarship - Angela Jeffery
Final report
The aim of this project was to develop a better understanding of Aboriginal fishing practices (past and present) through the development of educational materials.
This was to be undertaken as on-the-job training while working at Fisheries Victoria’s Marine and Freshwater Discovery Centre (MFDC) and, as a result of this scholarship, by researching indigenous fishing methods at the National Museum of Australia.
Evaluation of methods to assess abalone abundance
Effects of Trawling Subprogram: promoting industry uptake of gear modifications to reduce bycatch in the South East and Great Australian Bight trawl fisheries
Time and again, good research results have been wasted because there has been poor industry support, lack of industry consultation and a low level of effective extension of the results to grass-roots industry. Through Project 98/204, we have developed outstanding bycatch reduction results in the SETF with full industry support, high levels of consultation and an extensive extension process. Whilst all of the newsletters and videos have achieved a high level of Industry awareness of the bycatch reduction project, it is now time to promote and encourage industry uptake of the modfied codend designs. This will require hands-on work with the fishers on a one-on-one basis and further analysis of fish behaviour to reduce discards in trawl gear to a greater extent. This proposal seeks funds to support this phase of the project and continue the outstanding success of 98/204 in reducing the bycatch in SEF trawlers.
As evidence of the effective extension of the results of the current FRDC project 98/204, operators within the Great Australian Bight trawl fishery have shown keen interest in deploying modified gear to reduce bycatch in their fishery. As such, they have expressed their enthusiasm in participating in a project of this nature and wish to be included as participants within this proposal.The project budget and methods have been revised to reflect this.