Project number: 2019-214
Project Status:
Completed
Budget expenditure: $64,800.00
Principal Investigator: Ben Diggles
Organisation: DigsFish Services Pty Ltd
Project start/end date: 29 Jun 2020 - 29 Dec 2020
Contact:
FRDC
TAGS
White Spot Disease
Survey
Rac Qld
Fisheries Management
Disease
SPECIES
Black Tiger Prawn
Freshwater Prawns
King Prawns
Banana Prawns
Tiger Prawns

Need

This project was developed to document biosecurity protocols used on affected prawn farms on the Logan River in the two growing seasons since they restarted following shut down after the 2016-17 WSD incursion. Opportunistic sampling of non-commercial crustaceans (plankton, small crustaceans) was also undertaken in northern Moreton Bay and the Logan River during April and May 2020 at a time when it was known that WSSV was active in the environment. These samples have been archived and a stop work stage of the project has been enacted upon completion of this fieldwork.

If required, the samples collected can be tested by qPCR for WSSV in order to determine if they were acting as WSSV vectors and/or reservoirs in the Logan River and northern Moreton Bay. This information would be useful to inform the design of more detailed epidemiological studies of the distribution of WSSV in the environment of SE QLD that may be undertaken in the future. Review of the biosecurity protocols the prawn aquaculture industry in the region have implemented since 2016-17 to exclude WSSV vectors from their farms will also be undertaken to determine what worked, and what didn't. This information can then be used to inform biosecurity planning for the prawn farming industry on the Logan River moving forward to identify best practice for WSSV exclusion, in order to increase their chances of successfully farming prawns in the presence of the virus and reduce risk of WSSV spillback into wild crustacean fisheries.

Objectives

1. Interview prawn farmers and collect and archive field samples of potential WSSV vectors (microcrustaceans, small crabs, plankton)
2. After approval to conduct testing is obtained, testing of vector samples at BSL by qPCR to determine their WSSV status. Examine sub-samples of populations of any WSSV positive vector species using histopathology to determine if the presence of the virus is accompanied by pathological lesions or WSD disease.
3. Development of a report which combines the results of the vector testing with the outcomes of the onfarm biosecurity assessment to arrive at better understanding of how WSSV may be persisting in the environment of SE QLD, how the virus may be gaining entry into prawn farms on the Logan River, and how to improve prawn farm biosecurity to reduce risk of WSD outbreaks on prawn farms and WSSV spillback into wild fisheries.

Final report

ISBN: 978-0-9806995-5-5
Author: Ben Diggles
Final Report • 2020-10-29 • 5.92 MB
2019-214-DLD.pdf

Summary

The objective of this project was to undertake opportunistic plankton sampling and collect small non-commercial species of decapod crustaceans in northern Moreton Bay and near the intakes of the three prawn farms which remained operating on the Logan River during April and May 2020, at a time when it was known that WSSV was active in the environment. These samples were tested by qPCR for WSSV in order to determine if these taxa were acting as WSSV vectors and/or reservoirs and to inform the design of more detailed epidemiological studies of WSSV in the environment of South East Queensland (SE QLD) that may be undertaken in the future. Interviews with prawn farmers operating on the Logan River were also conducted to document the biosecurity protocols used on affected prawn farms during the two growing seasons since they restarted following fallowing after the 2016-17 WSD incursion.
 
A range of wild taxa sampled near or on prawn farms on the Logan River were found to be qPCR positive (Ct 36.00,
 
A significant risk factor for all farms appeared to be intake of water from the Logan River after a large rainfall event in February 2020. As WSSV was found at low levels in a broad range of taxa, and at high levels in some wild prawns and crabs near prawn farms, this suggests that WSSV has become embedded in the lower trophic levels of aquatic food chains in northern Moreton Bay and on the Logan River. The virus is therefore likely to remain in this region for the foreseeable future, signalling an urgent need for prawn farmers to further increase biosecurity as they farm in the presence of the virus. As long as the White Spot Biosecurity Area remains in place, the economic impact on the commercial bait prawn and baitworm fisheries in Moreton Bay will continue to accumulate over time, potentially exceeding that experienced by the prawn farming industry

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