13 results

Understanding shelf-break habitat for sustainable management of fisheries with spatial overlap.

Project number: 2004-066
Project Status:
Completed
Budget expenditure: $514,126.61
Principal Investigator: Caleb Gardner
Organisation: University of Tasmania (UTAS)
Project start/end date: 28 Oct 2003 - 30 Aug 2007
Contact:
FRDC
TAGS
Population Dynamics
Oceanography
Habitat
Fishing Gear
Environmental Impact
SPECIES
Mirror Dory
Pink Ling
Blue Grenadier
Giant Crab
Blue-eye Trevallas

Need

The need for this project was identified by fishery managers and industry and addresses high priority strategic research areas identified by both state and national fisheries organisations. It is research that targets a high priority need across Australian fisheries: understanding the effects of fishing activities on fish and their ecosystems. The need for research is compounded in shelf-break habitats due to: (a) scarcity of basic information about shelf break habitats, (b) slow growth of many species in this region implying less resilience to impacts, (c) interaction effects between different sectors that may compound impacts.

The research need on addressing interaction between different sectors will be specifically addressed here in relation to the interaction between trawl and crab trapping sectors. This interaction between different fishing sectors is not unusual and is likely to be repeated in the future – work conducted here will assist in providing a template for resolution.

Understanding shelf-break habitat for sustainable management of fisheries with spatial overlap was identified as the number 1 research priority for Tasmanian crustacean research by both DPIWE and representatives of the Tasmanian crustacean fishing industry at the Tasmanian Crustacean Research Advisory Group.

The project focus is also consistent with strategies developed by the Commonwealth agencies involved in management of industries based around the shelf-break: the Commonwealth Government and the Department of Agriculture, Fisheries and Forestry Australia (AFFA). It is targeted to the FRDC program of Natural Resource Sustainability through the strategies of “Interactions between fish and their ecosystems” and “Effects of fishing activities on fish and their ecosystems”.

Objectives

1. Define and map key habitats on the shelf edge (~80-180 fm) at key locations around Tasmania where fisheries using different gear types interact.
2. Evaluate their resistance and resilience to impact from fishing gears based using the semi-quantitative 'Ecological Risk Assessment' framework
3. Detail the distribution of exploited shelf-edge species in relation to habitat features
4. Evaluate ecosystem links within habitats based on trophic, temperature and current-flow data
5. Evaluate using video to obtain stock assessment information such as abundance, sex ratio, condition and size of target species, primarily the giant crab

Final report

ISBN: 9.78E+12
Author: Caleb Gardner
Final Report • 2010-05-18 • 63.94 MB
2004-066-DLD.pdf

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
Contact:
FRDC
TAGS
Stock Assessment
Laboratory Procedures
Fisheries Management
Analytics
Ageing
SPECIES
Blue-eye Trevallas

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.

Development of an artificial neural network for automated age estimation

Project number: 1998-105
Project Status:
Completed
Budget expenditure: $132,072.00
Principal Investigator: Simon Robertson
Organisation: Agriculture Victoria
Project start/end date: 14 Jun 1998 - 31 Mar 2002
Contact:
FRDC
TAGS
Stock Assessment
Analytics
Ageing
SPECIES
Southern Bluefin Tuna
Gemfish
Black Bream
Snapper
Deepwater Flathead

Need

Current age determination methods, even when aided by image analysis software still depend on interpretation by an experienced "reader". The process of ageing is also laborious, time consuming and hence, relatively expensive. For production ageing, where there is an ongoing requirement for age estimates, there is a problem of consistency of interpretation. At present, when readers change, there is a substantial training and verification period needed to ensure that the new reader is interpreting otolith structure in a consistent and correct manner. Automatic ageing would have the primary advantage of being a far more objective method than is possible with even the best training, reducing discrepancies both between readers and organisations. This factor will increase the precision of estimates and therefore provide greater confidence for the stock assessment process. Benefits associated with the development of this technique also include the reduced sample processing time which would increase the number of samples able to be processed and hence, reduce the cost.

The pilot project which has been completed has demonstrated the potential for artificial neural networks to objectively and consistently classify samples of some species. With refinements of the system, it should be applicable to any species for which production ageing is required.

Objectives

1. Compare the effect of different forms of data input on the performance of an ANN model for automatic ageing.
2. Compare the effect of different forms of ANN models on their performance.
3. Develop a protocol for the application of an ANN model to the process of automatic ageing.

Final report

ISBN: 0-7311-5038-4
Author: Simon Robertson
Final Report • 2002-02-28 • 1.25 MB
1998-105-DLD.pdf
View Filter

Research

Category

Species

Organisation