3 results

Identification of natural mudworm species in South Australian Pacific oyster (Crassostrea gigas) stocks

Project number: 2003-402
Project Status:
Completed
Budget expenditure: $5,000.00
Principal Investigator: Gary Zippel
Organisation: South Australian Oyster Research Council Pty Ltd (SAORC)
Project start/end date: 29 Jun 2003 - 1 Feb 2004
:

Need

In South Australia and all other countries spionid polychaete (‘mudworm’) infestations are a major problem for oyster growers and have large financial impacts, it has been recorded by individual oyster growers to lose up to $50,000 in stock in one year. There are 150 licensed oyster growers in SA and if this loss caused by mudworm was calculated at 5% of the extreme cases at $2500 per licence holder the economic cost to industry would equate to $375,000 per annum. These losses may not be through mortality, but growers experiencing mudworm problems provide extra oysters when selling to their buyers to compensate for losses from mudworm infestations. In South Australia the species causing damage are not well known. It is for this reason that South Australian Oyster Research Council (SAORC) want to implement a survey to gain an understanding of mudworm species found in SA to assist industry with the management of this pest.

The industry views the need to understand and control mudworm infestations as the losses caused by these worms could potentially be reduced if known species are identified and management techniques can be put in place to reduce infestation rates. However, the farmer’s ad-hoc management approaches have failed to stop or reduce mudworm infestation rates, as farmers have reported that with even the best management practices they still experience mudworm infestations. Due to this, the South Australian Oyster Research Council has identified two experts in mudworm identification to work with SA scientists to survey mudworm species and suggest management practices to SA oyster growers to potentially reduce the problem. Mudworm surveys have been conducted in many other oyster growing areas and different species have been identified which have different life cycles, hence, different forms of management practices are required to reduce infestations.

If this project can achieve a 50% reduction in mudworm infestations or mortality after harmful species have been identified and farmers have implemented management techniques developed through the extension training workshop, the savings to growers will be approximately $187,500 dollars over the next year. The reduction in oyster growers production costs is a small component, the benefits will be seen in the future through increased consumer confidence, hence, increased sales of SA oysters.

In addition, minimising the impact of mudworm on the Pacific oyster aquaculture industry in SA will also strengthen the confidence of new growers and investors in this industry thereby encouraging its further development.

Objectives

1. Design and conduct a survey of spionid polychaetes (mudworm) to identify natural species and life cycle from South Australian oyster growing regions.
2. Work with SA scientist to train them in the identification of SA mudworm species.
3. Identify the best management techniques to reduce mudworm infestation rates in SA.
4. Communicate advice to farmers through a workshop format.

Final report

Author: Gary Zippel
Final Report • 2004-08-11 • 478.67 KB
2003-402-DLD.pdf

Summary

Under a joint arrangement between Seafood Services Australia (SSA) and the South Australian Oyster Research Council (SAORC), a project was developed to investigate mudworm in South Australia.

A minor mudworm survey was carried out in which between one and three dozen oysters from seven different growing areas were sampled for mudworm species, the survey involved industry members, scientists and industry experts and was implemented over a 2-day period in Adelaide. The survey only touched on the edge on the mudworm issue in South Australia, but provided a forum to train South Australian industry and scientist representatives in the sampling, preservation and the identification of mudworm.

The mudworm species identified were different from previously recorded species; which raised concerns and questions regarding the problematic species in SA.  The confusion over the identification of some of the South Australian mudworm species highlighted the need for more investigative work in this area.

Height in the water column is considered the best management method for controlling mudworm infestations on the farm; this is very much supported through the extensive research conducted by Dr Handley. Dr Handley presented on mudworm ecology and management techniques at an industry workshop held in Port Lincoln to build awareness and to reiterate to industry the potential impact mudworm can have on oyster stocks, given the right environmental conditions for growth.

The results from the survey demonstrated that future work on mudworm is required. It is SAORC aim to expand on the work done to date to identify the species causing the blisters in various SA oyster growing areas and understand enough of their life cycles to recommend effective control strategies. Then management techniques suitable to the grower can be developed, ultimately giving growers the methods to farm oysters without the financial burden of mudworm infestations.

SCRC: Visiting Expert: Dr Ben Madin and Ms Rachel Gordon, AusVet Animal Health Services

Project number: 2013-721
Project Status:
Completed
Budget expenditure: $0.00
Principal Investigator: Trudy McGowan
Organisation: South Australian Oyster Research Council Pty Ltd (SAORC)
Project start/end date: 31 Mar 2013 - 29 Sep 2013
:

Final report

ISBN: 978-1-925982-06-0
Author: Trudy McGowan
Final Report • 2013-04-09 • 673.07 KB
2013-721-DLD.pdf

Summary

Over the last ten years the South Australia (SA) Oyster Industry has nearly doubled its output, and now contributes nearly one hundred million dollars annually to the Gross State Product (GSP). Coincident with this growth has been an increasing sense within the industry that the mortality rates of juvenile oysters during the late autumn/winter period has been increasing and has now become a significant impediment to increasing production. This increase in mortality has been labelled South Australian Mortality Syndrome (SAMS).

In September 2012 a workshop was held for producers in Port Lincoln, with the intention of describing and evaluating the mortality being experienced across the SA growing zones. The input from a large number of producers was assessed and a report of this meeting produced for the South Australian Oyster Research Council (SAORC) and distributed to the industry.

Two very clear messages emerged from the presentations given by subject experts: the importance of normal, and the availability of information. A process of identifying the gaps and possible research to help overcome the deficits were identified for the development and appraisal of any future research. These themes were:

  1. Better understanding of the normal oyster
  2. The nutritional requirements of SA Oysters
  3. Information management
  4. Information extension

Ensuring that producers are aware of these themes will help to develop understanding of the decisions that are made in funding research, and ensure the successful extension and integration of research findings into the industry.

Workshop to facilitate epidemiological analysis of unexplained mortality of South Australian Pacific Oyster

Project number: 2012-051
Project Status:
Completed
Budget expenditure: $36,000.00
Principal Investigator: Charles Caraguel
Organisation: South Australian Oyster Research Council Pty Ltd (SAORC)
Project start/end date: 16 Sep 2012 - 31 Mar 2013
:

Need

For at least the last 12 years SA growers have noticed unexplained mortality of Pacific Oysters. Tests for Pacific Oyster Mortality Syndrome (OHSV-1uvar) have come up negative each time.

The mortality was first documented in Smokey Bay and is now documented in all the major producing Bays in South Australia, including Coffins Bay, Smoky Bay, Cowell and Ceduna (Denial Bay). Mortality rates have been increasing over time. Losses of between 5-20% each year which equates to between $1.8-$7 million per annum.

Mortalities are generally associated with seasonal temperature related stress in the animals. The timing of the mortalities varies from year to year within specific bays. Mortlaities do not follow a geographical distribution with some sites more affected than others. Anacodatal advice from growers indicates that sites with slower growth rates don’t suffer as badly has highly productivity bays.

In recent years, mortalities have been experienced in the major producing bays. Anacdotal adivce from growers indicates that mortality is particularly in smaller to medium size oysters, but mortality is also occuring in mature stock.

There does seem to be a genetic link to the mortality with anacdotal reports of 100 % mortality of certain “batches”. Given this link the breeding program is breeding for resistance to these unexplained mortality events. Susceptibility varies depending on the family line.

In response some growers are lifting the height of the oysters which reduces the mortlaity rate but slows the growth rate and increases the growout time. There is concerm within the industry that this is not an economically viable solution in the long term.

Research has been proposed to investigate unexpained mortality however industry are supportive of an epidemiological analysis of exisiting data and knowledge to narrow the likely causes so that any future research is focused on likely causes.

Objectives

1. Bring together growers and epidemiologists to define, describe and quantify the scope of unexplained mortality of Pacific Oysters in South Australia
2. Develop and test range of hypothetical causes of the mortalities based on best available information and expertise
3. Identify any gaps in the knowledge or expertise required to test the hypothetical causes
4. Refine and seek agreement on a future Research and Development plan that addresses unexplained Pacific Oyster mortality in South Australia
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