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Environment
Environment

Eastern Bass Strait deep water trawl fishery stock assessment

Project number: 1984-073
Project Status:
Completed
Budget expenditure: $0.00
Organisation: Agriculture Victoria
Project start/end date: 28 Dec 1987 - 31 Dec 1987
:

Objectives

1. Obtain preliminary estimates of distribution & abundance,
2. parameters determining population dynamics, & potential annual yields, for commercially important spp of demersal fish at depths between 400-700m in the underdeveloped sector of eastern Bass Strait

Using information for 'data-rich' species to inform assessments of 'data-poor' species through Bayesian stock assessment methods

Project number: 2002-094
Project Status:
Completed
Budget expenditure: $176,237.00
Principal Investigator: David Smith
Organisation: Agriculture Victoria
Project start/end date: 29 Sep 2002 - 30 Nov 2005
:

Need

Over 300 species are caught in the SEF, of which around 100 have commercial value. Twenty five species comprise around 90% of the landed catch. Each year, however, quotas are set for only around 17 species. There are 10 of these species for which there is (or has been) some formal stock assessment (that may not occur every year). For all of the remaining quota species and some of the more important non-quota species, no formal assessment is undertaken and the only assessment that can be made is based on investigation of trends in catch and effort and size distribution and anecdotal input from scientists and industry. There is simply not enough resources to undertake formal stock assessments for the wide range of commercial species landed in the SEF. Yet, each of these species is an important component of the catch of fishers. If the fishery is to continue to operate in its current form and meet the strategic assessments required under the EPBC Act, some form of formal assessment is required.

A recently completed ARF project (Production parameters from the fisheries literature for SEF-like species - Project no R99/0308) demonstrated the utility of using information for "similar" species when conducting assessments for SEF species. Using key parameters such as the virgin biomass, the rate of natural mortality, and the “steepness” of the stock-relationship relationship, a simple formula was developed for identifying “similar” stocks / species and an algorithm was developed for constructing prior probability distributions for these parameters. The resultant distributions can be used in Bayesian stock assessments and as the basis for sensitivity tests when applying other methods of stock assessments. The current project will refine the prior distributions for the production parameters and develop and test methods of stock assessment that use the results of assessments for well-studied species in a formal manner to inform assessments of ‘data-poor’ species. If successful, the methods developed would lead to significant benefits not only for the assessment and management of "data poor" SEF low priority, by-product and by-catch species, but also for a range of new and developing fisheries in Australia.

Objectives

1. Expand the database of production parameters for SEF-like species
2. Develop prior probability distributions for steepness and the coefficient of variation about the stock-recruitment relationship using Bayesian meta-analysis
3. Develop a Bayesian framework within which the results for data-rich species can 'inform' assessments for data-poor species.
4. Apply the framework to three case-studies to determine the robustness of the framework.
5. Test the framework by means on Monte Carlo simulation

Final report

Environment

Stock discrimination of blue-eye trevalla (Hyperglyphe antarctica) from Australian shelf waters and offshore seamounts and New Zealand

Project number: 2003-045
Project Status:
Completed
Budget expenditure: $269,037.00
Principal Investigator: Jeremy Hindell
Organisation: Agriculture Victoria
Project start/end date: 30 Aug 2003 - 30 Apr 2006
:

Need

Blue-eye trevalla is an important species in the South East Fishery. Blue-eye trevalla is taken in large quantities by the trawl and non-trawl sectors in south eastern coastal waters and around offshore seamounts. Despite the high value of this species in the trawl and non-trawl fisheries, however, there is limited information on the stock structure and appropriate management units. Bolch et al. (1993) concluded there was sufficient gene flow to prevent genetic differentiation between blue-eye trevalla off Tasmania, South Australia and NSW, but the sample sizes were small, there are limitations to allozyme electrophoresis (the method they used), and they did not sample fish from NZ. Ward and Last (1993) suggested that, given the known limitations of allozyme electrophoresis, further genetic studies based on mitochondrial DNA analyses and larger samples be undertaken. As a consequence, the relationship between fish caught off the south eastern Australian coast and those taken from offshore seamounts is unknown. The need to identify the stock structure of Blue-eye trevalla has also been identified as a high priority by the blue-eye working group and SEFAG.

In recent years, developmental trawl fishing has been occurring in the East Coast Deep Water (ECDW) fishery. Significant amounts of blue-eye trevalla have been caught in this fishery from grounds well to the east of 157ºE, and currently these fish are under the same quota restrictions that apply to the rest of the SEF trawl fishery. The large distances between the ECDW fishing grounds and grounds where most of the east coast blue-eye are caught has led fishers to question whether the ECDW fish can be considered part of the stock upon which the TAC was based. There is an urgent need to assess the stock structure of blue-eye trevalla caught throughout the SEF, the ECDW fisheries and New Zealand. The results from a study assessing the stock structure of this species will provide managers with information on potential management units.

A proposal to investigate the relationships between blue-eye trevalla caught in the ECDW zone and the SEF was submitted to AFMA in 2001, and although supported, it was not funded at this time for a number of reasons. In response to suggestions from AFMA, the MACs and SEFAG, it was decided that the proposal should be re-submitted in 2002. To address suggestions from industry and management groups that the stock structure of blue-eye needed to be evaluated over a much larger area, the extent of the project was expanded to include blue-eye samples from across south eastern Australia, including offshore seamounts (such as those off Tasmania, Norfolk and Lord Howe Islands) and New Zealand.

Objectives

1. To use otolith microchemistry and shape analyses to assess the stock relationships between blue-eye trevalla caught in 8 regions (east , west and south Tasmania, west Victoria/South Australia, east Victoria and East Coast Deep Water, Queensland/NSW shelf waters and the west coast of New Zealand)(YEAR 1).
2. To a) validate the results from otolith microchemistry and shape analyses, and b) better assess stock structure of blue-eye trevalla in the regions identified in objective 1, using mitochondrial DNA analyses (YEAR 2).
3. To determine a suitable approach for assessing stock structure in blue-eye trevalla in south-east Australia, and make recommendations on the most appropriate methods for future work (including sample size and spatial/temporal sampling), to better understand the stock structure of blue-eye trevalla in the SEF and ECDW fisheries.
4. To utilise the results from all analyses in the assessment and management of blue-eye trevalla via meetings of the relevant stakeholder groups including SETMAC, SENTMAC, AFMA and the blue-eye working group.

Final report

ISBN: 1-74146-575-3
Author: Jeremy Hindell
Final Report • 2006-12-13
2003-045-DLD.pdf

Summary

This work is principally about identifying the best method for examining the population structure of blue-eye trevalla (Hyperoglyphe antarctica). It is not, and was never intended to be, an exhaustive assessment of stock structure of blue-eye trevalla in Australia’s Fishing Zone. As such, findings on stock structure per se are preliminary only.
 
Blue-eye trevalla are a key economic species in Australia’s Fishing Zone. They are caught from NSW, around Tasmania, to Western Australia. Blue-eye are caught in both the trawl and non trawl fishing sectors, within which they are regarded as non-target and target species, respectively. The total allowable catch in 2004 was 743 tonnes across the non-trawl and trawl sectors, but only 651 tonnes were actually caught. Nonetheless, this catch had an estimated market value of more than $5 million AUD (based on average prices paid at the Sydney Fish Market). Less than 1% of blue-eye landings were discarded across the fisheries. The non trawl catch in 2004 was 567 tonnes, compared to 84 tonnes taken in the trawl sector. Most of the non-trawl catch is now taken by long lines off the east coast of Tasmania; since 2002 there has been a decline in the catch taken on drop lines. Since 1999 there has also been a decline in catches of blue-eye in the trawl sector.
 
Blue-eye trevalla are managed as a single stock. Research to date supports this management regime. Results from previous work on genetics (allozyme analyses) suggest that gene flow is sufficient to prevent genetic differentiation among fish collected from seamounts off NSW to those off Tasmania, and around the Tasmanian coast. Tagging studies suggest that juvenile fish (around 50 cm length) can move from NSW slope waters to those off eastern Tasmania; still smaller individuals (< 20 cm in length) can possibly drift between Australia and New Zealand. Despite this evidence, there is some uncertainty in whether fish from offshore seamounts, particularly those in the East Coast Deep Water, are the same
‘stock’ as those along Australia’s continental shelf.
 
This study used 4 different approaches (otolith shape analysis, otolith elemental microchemistry, otolith stable isotope analysis, mitochondrial DNA) to compare which method best delineated subpopulations of blue-eye sampled from 6 regions of the South East Fishery (SEF: NSW, east Victoria, east, south and west Tasmania, and South Australia), the East Coast Deep Water region, and New Zealand – 8 regions in total.
 
Samples of fish were collected opportunistically from commercial landings in each of these regions. Only fish with a fork length of approximately 50 cm or less were used. This enabled us to restrict the age of the fish we sampled, thereby ensuring that patterns among regions were a reflection of differences in stock structure rather than age. We collected at least 40 samples (individual fish) from all of the regions except NSW, from which we could only collect 30 fish (20 of which were of the ‘correct’ size). For each fish, we recorded the fork length, identified the sex (where possible), removed the otoliths for shape and microchemical analyses, and took tissue samples for genetic analyses.

Influence of water circulation patterns in Bass Strait on recruitment success and stock differences in scallops

Project number: 1987-117
Project Status:
Completed
Budget expenditure: $0.00
Organisation: Agriculture Victoria
Project start/end date: 27 Dec 1993 - 30 Dec 1993
:

Objectives

1. Insight into stock relationships & recruitment success by defining conditions (spawn times, locations, weather, tides etc.)
2. Facilitating larvae dispersal between beds
in which existing beds may be self-seeding
& which transport larvae out of Bass Strait/to unsuitable areas
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