Recurrent harmful algal blooms in Tasmanian waters (Gymnodinium in the South and Alexandrium on the East Coast) have impacted Oyster, Mussel, Abalone and Rock Lobster industries, necessitating the implementation of biotoxin monitoring programs and harvest closures during high risk periods. It is currently unknown whether Periwinkles can accumulate paralytic shellfish toxins (PST) from Tasmanian microalgal blooms and a conservative risk management approach has been taken thus far to protect both public health and market access.
Unlike bivalve shellfish, Abalone and Rock Lobster, there is currently no clearly defined biotoxin management plan for Periwinkles in Tasmania. As grazers, Periwinkles are loosely grouped with Urchins and Abalone, the latter of which are a proven PST risk. This Abalone biotoxin sampling plan is triggered when Tasmanian Shellfish Market Access Program (ShellMAP) closes bivalve harvest areas due to PST risk. In a conservative approach, the current recommendation is PST analysis of 20 pooled Periwinkles per Abalone block on at least a monthly basis to maintain market access. This presents a considerable cost burden to the small dive fishery and interrupts harvest operations, as PST sampling of Periwinkles is required if elevated PST are detected in Abalone, which are known to hold onto PST for longer time periods in between blooms (years).
To date, the vast majority of Periwinkle samples that have been analysed for PST were collected from weak or no bloom years or regions. Evidence from French tank trials exposing the common European Periwinkle (Littorina littorea) to Alexandrium minutum cysts containing PST showed significant toxin uptake (0.2 mg PST/kg) within six days of exposure (Neves et al, 2015). It remains unknown whether commercially harvested Tasmanian Periwinkles (Lunella undulata) are at risk of PST accumulation and if the current conservative monitoring approach is commensurate to risk. In such scenarios, risk managers will commonly outsource a preliminary risk assessment (known as a risk profile). Risk profiles are an important tool for risk managers and industry. They provide a summary of all information pertinent to food safety associated with the specific hazard/food combination. The purpose of a risk profile is to assist initial risk management activities, such as identifying future actions required (if any), and the options for food safety management programs. They also inform the level of resourcing required to control the hazard/food pairing.
This project will deliver an urgently required risk profile for PST in Periwinkles to inform future actions (if any) and provide options for cost-effective food safety management programs. This profile will:
1. Determine the risk of PST accumulation in Periwinkles in Tasmania as a result of harmful microalgal blooms during high risk exposures at peak algal bloom densities in the field and in tank trials.
2. Outline potential management options and knowledge gaps, should risk management be necessary. This includes an assessment of whether the bivalve PST regulatory limit is appropriate to use in Periwinkle risk management (currently based on shellfish serving size of 100-400g) and the spatial variability associated with sampling.
References
Neves, Raquel AF, et al. "Responses of the common periwinkle Littorina littorea to exposure to the toxic dinoflagellate Alexandrium minutum." Journal of Molluscan Studies 81.2 (2015): 308-311.
