Project number: 2017-086
Project Status:
Completed
Budget expenditure: $879,224.82
Principal Investigator: Gustaaf Hallegraeff
Organisation: University of Tasmania
Project start/end date: 14 Mar 2018 - 7 Jul 2021
Contact:
FRDC

Need

The $84 M lobster industry has been impacted by seasonal Tasmanian closures (up to 5+ months) due to PST contamination of hepatopancreas (HP) notably in the St Helens and Maria Island regions (up to 4 mg STX.diHCl/kg), and up to Flinders Island, with an estimated lost revenue cost of 780k (Campbell et al 2013). While only trace levels of PSTs have been detected to date in lobster tail meat, HP contamination poses significant trade barriers for key markets such as China and Hong Kong. While cooking of lobsters did not release biotoxins into the cooking water, HP is a sought after foodstuff (mainly used as a dipping sauce for tail meat) and consumed by 16% of fishers on the Tasmanian east coast and 22% on the west coast, but this has since decreased due to public health warnings. Limited evidence suggests that PST contamination of lobsters may also occasionally occur in South Australia and Victoria.

The monitoring, management and mitigation approaches for biotoxin risks in crustaceans (as spelled out in the DPIPWE Rock Lobster Biotoxin Plan and Decision Protocol) remain poorly developed. The current approach uses bivalve PST monitoring as a trigger for lobster testing, with a very limited number (5) animals tested at a prohibitive cost of 5k, which if positive (>0.8 mg/kg STX eq) leads to lengthy closures of large fishing zones.

The proposed work will refine monitoring tools to reduce the costs associated with PST biotoxin risk management of Southern Rock Lobster, including the application of cheaper and faster (and hence more frequent and more reliable) PST testing and also explore whether tests can be conducted in a non-destructive manner using haemolymph as a proxy.

In addition, tank studies of PST in lobster and field studies on the variation in toxicity, and the validation of a rapid test kit will help to inform the effectiveness of the current geographical zones in the management plan.

Potential impact of PST on lobster vigour will also be investigated using a combination of tank exposure and blood biomarker studies, the latter once calibrated also applied to Tasmanian field surveys.

Objectives

1. Assess the applicability of Neogen PST test kits for lobster viscera
2. Exploration of Neogen PST tests on lobster haemolymph as a proxy for lobster viscera PST contamination
3. Determination of the impact of PST accumulation on lobster vigour
4. Improved definition of East Coast Tasmanian lobster management zones, based on improved understanding of dietary origin of PST (from tank studies), and improved understanding of variability ( from field studies ).

Final report

ISBN: 978-1-922708-32-8 978-1-922708-31-1
Authors: Gustaaf Hallegraeff Alison Turnbull Andreas Seger Juan Dorantes-Aranda Caleb Gardner Quinn Fitzgibbon and Hillary Revill
Final Report • 2023-04-01 • 8.04 MB
2017-086-DLD.pdf

Summary

To examine toxicokinetics of PST in Southern Rock Lobster, an experimental study was undertaken in a biosecure aquaculture facility in South Australia. Adult male lobsters were fed highly toxic mussels (6 mg STX.2HCl equiv. kg−1) sourced from the Tasmanian east coast for 4 weeks, then allowed to depurate for a further 5 weeks. Control (fed non-toxic mussels) and exposed lobster were harvested at regular intervals, tissues dissected and analysed for PST. The lobsters rapidly accumulated PST in the hepatopancreas (exponential rate of 6% per day), exceeding the bivalve ML within one week, and reaching a maximum of 9.0 mg STX.2HCl equiv. kg−1. Once toxic feed was removed, the lobster depurated at a rate of 7% per day. Toxins were found in lobster antennal glands at concentrations two orders of magnitude lower than found in the hepatopancreas. This is the first report of PST in lobster antennal glands which, along with the gills, represent possible excretion routes for PST. However, PST were not detected at significant levels in the lobster haemolymph, which rules out the possibility of nondestructive sampling of lobsters for biotoxin analyses.

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