Abstract
Paralytic shellfish toxins (PST) are found in the hepatopancreas of Southern Rock Lobster Jasus edwardsii from the east coast of Tasmania in association with blooms of the toxic dinoflagellate Alexandrium catenella. Tasmania’s rock lobster fishery is one of the state’s most important wild capture fisheries, supporting a significant commercial industry (AUD 97M) and recreational fishing sector. A comprehensive 8 years of field data collected across multiple sites has allowed continued improvements to the risk management program protecting public health and market access for the Tasmanian lobster fishery. High variability was seen in toxin levels between individuals, sites, months, and years. The highest risk sites were those on the central east coast, with July to January identified as the most at-risk months. Relatively high uptake rates were observed (exponential rate of 2% per day), similar to filter-feeding mussels, and meant that lobster accumulated toxins quickly. Similarly, lobsters were relatively fast detoxifiers, losing up to 3% PST per day, following bloom demise. Mussel sentinel lines were effective in indicating a risk of elevated PST in lobster hepatopancreas, with annual baseline monitoring costing approximately 0.06% of the industry value. In addition, it was determined that if the mean hepatopancreas PST levels in five individual lobsters from a site were <0.22 mg STX equiv. kg−1, there is a 97.5% probability that any lobster from that site would be below the bivalve maximum level of 0.8 mg STX equiv. kg−1. The combination of using a sentinel species to identify risk areas and sampling five individual lobsters at a particular site, provides a cost-effective strategy for managing PST risk in the Tasmanian commercial lobster fishery.
Highlights
Recurrent blooms of the toxic dinoflagellate A. catenella (Whedon and Kofoid) Balech have occurred in winter on the east coast of Tasmania since 2012 [1]
Closures may be for extended periods, with the maximum paralytic shellfish toxins (PST) level detected of 150 mg STX equiv. kg−1 in mussels in 2017 grossly exceeding the maximum level (ML) [1]
All PST results reported are expressed in mg STX equiv.kg−1 in line with research on PST in Southern Rock Lobster has been reported following Codex guidelines current Australian regulatory requirement for PST in bivalve shellfish and use
Summary
Recurrent blooms of the toxic dinoflagellate A. catenella (Whedon and Kofoid) Balech have occurred in winter on the east coast of Tasmania since 2012 [1]. The species involved is highly toxic, resulting in paralytic shellfish toxins (PST) increasing rapidly in bivalve molluscs. Public health and market access risks are managed through weekly monitoring of toxin levels in shellfish flesh, with closures occurring when PST exceeds the domestic regulatory maximum level (ML) of 0.8 mg saxitoxin (STX) equiv. Closures may be for extended periods (over 20 weeks; unpublished data), with the maximum PST level detected of 150 mg STX equiv. Kg−1 in mussels in 2017 grossly exceeding the ML [1]. During the initial bloom in 2012, PST was detected in multiple bivalve species (oysters, mussels, scallops, and clams) and several non-traditional vectors (rock lobsters, abalone, and giant crab) [2].
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