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Environment
Environment
Environment
Environment
PROJECT NUMBER • 1997-110
PROJECT STATUS:
COMPLETED

Age validation from tagged school and gummy sharks injected with oxytetracycline

The project ‘Age Validation from Tagged School and Gummy Sharks Injected with Oxytetracycline’ (FRDC Project 97/110) follows on from four successfully completed projects. These are the ‘Southern Shark Age Validation’ (FRDC Project 91/037), ‘Southern Shark Nursery’...
ORGANISATION:
Agriculture Victoria
Environment
PROJECT NUMBER • 1996-162
PROJECT STATUS:
COMPLETED

Southern shark tag database

As part of the projects, all available tag release-recapture data available from shark tag releases during 1947-56, 1973-76, and 1990-99 have been validated and consolidated in the Southern Shark Tag Database developed in Microsoft ACCESS. The database is routinely updated and has facility for...
ORGANISATION:
Agriculture Victoria

Southern rock lobster recruitment study

Project number: 1995-018
Project Status:
Completed
Budget expenditure: $178,850.00
Principal Investigator: David Hobday
Organisation: Agriculture Victoria
Project start/end date: 16 Aug 1995 - 7 Sep 2000
:

Objectives

1. To develop catch forecasting methods based on recruitment indices of puerulus settlement and juvenile abundance.
2. To determine the movement pattern from juvenile nurseries to commercial fishing grounds.
3. To compare the number of juveniles with the number of adults and test the assumptions of stock depletion assessments.
4. To investigate the density dependent effects on mortality at different life stages.

Final report

ISBN: 0-7311-4539-9
Author: David Hobday
Final Report • 2000-05-15 • 1.21 MB
1995-018-DLD.pdf

Summary

The southern rock lobster (Jasus edwardsii) is found in Australia’s southern waters from south-west Western Australia to southern New South Wales, including the waters around Tasmania.  In 1996/97, 4,835 tonnes of southern rock lobster were landed in Australia with the highest catch from South Australia (52%) followed by Tasmania (37%), Victoria (10%) and Western Australia (1%) (Anon 1999).  The Victorian component of this catch was 464 tonnes in 1996/97 with 403 tonnes caught in the Western and 61 tonnes in the Eastern Management Zones (Anon 1998).
The larval stages of the southern rock lobster are relatively long, ranging between 12 and 20 months from hatching of eggs to settlement of pueruli.  The planktonic larvae or phyllosomas are dispersed by ocean currents; however, this process is not well understood in southern Australia.  Phyllosomas metamorphose into pueruli larvae which settle on inshore reefs.  The study of settlement of pueruli is being conducted in all southern Australian states.  
Little is known about the relationships between larval settlement, juvenile abundance and adult abundance for Jasus edwardsii in Australia; however, such relationships have been determined for the western rock lobster (Panulirus cygnus) and used to predict catches four years in advance.
The present study aimed to establish larval and juvenile monitoring at three sites in central Victoria, Flinders, Ocean Grove and Torquay.  Larval collection sites were set up and monitored monthly.  Twice yearly, commercial fishers set pots (including fine-meshed research pots) in reef areas near the settlement sites to monitor juvenile and adult abundance.  Extensive tagging was carried out during this fishing and movement of subsequent recaptures analysed.
 
Settlement of larvae was very low at all sites and showed no pattern.  The study sites appear to be in a very low settlement area compared with results from other work to the southwest at Apollo Bay.  
Juvenile and adult abundance was monitored at each site although some practical problems were experienced in fishing near the Flinders site.  There was a lack of animals below 60 mm carapace length in the catches and further work needs to be undertaken to enable sampling of these early benthic stages.
Tagging showed that overall movement was localised with some movement occurring from inshore reefs to deeper water.  A low level of movement was observed but a small proportion of immature females and one male undertook large migrations in a south-westerly direction towards King Island.

The present study has begun the process of collection of long-term data monitoring abundance of larval settlement and juvenile abundance for catch prediction.  Abundance of juveniles increased during the study and based on growth data from tagging corresponded with the high larval settlement observed at Apollo Bay during 1995.  It appears that catch prediction may be achievable in the study site where lobsters are recruited to the fishery at around 4-5 years.  Slower growth in western Victoria with lobsters recruiting to the fishery at 5-8 years may weaken any relationships between larval settlement and recruitment. Monitoring of pre-recruits should be increased for development of indices for short-term predictions.
Environment
PROJECT NUMBER • 1993-100
PROJECT STATUS:
COMPLETED

Evaluation of methods to assess abalone abundance

The issue of how best to survey abalone populations to obtain estimates of abundance has been the subject of debate among fisheries biologists for many years. In an attempt to resolve this issue we compared and evaluated abalone abundance estimated by the following methods: Transect survey,...
ORGANISATION:
Agriculture Victoria
Environment
PROJECT NUMBER • 1983-032
PROJECT STATUS:
COMPLETED

Port Phillip Bay and Bass Strait scallop research

During the 3 years of the study, scallop spatfall was observed to occur over a short period (October-December) after the scallops had spawned in spring. Growth was rapid and scallops reached an acceptable harvestable size of 70mm within 16 months. Spatfall one year can therefore be related to...
ORGANISATION:
Agriculture Victoria
Environment

Movement and re-aggregation of blacklip abalone in response to intensive fishing

Project number: 1995-165
Project Status:
Completed
Budget expenditure: $116,068.00
Principal Investigator: Harry Gorfine
Organisation: Agriculture Victoria
Project start/end date: 28 Jun 1996 - 29 Sep 1998
:

Objectives

1. To determine the extent of migration and re-aggregation of a blacklip abalone population in response to fishing
2. To describe differences between pre and post-fishing spatial distribution patterns in blacklip abalone population
3. To determine the growth rates of a "stunted" abalone sub-stock

Final report

ISBN: 0 7311 4207 1
Author: H.K. Gorfine R.A. Officer C.D. Dixon
Final Report • 1998-09-10 • 2.09 MB
1995-165-DLD.pdf

Summary

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.

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