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.
Final report
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.
