MISA - Marine Innovation SA

• Seafood Product Quality & Value-adding
• Aquaculture Innovation
• Ecosystem Services
• Biosecurity

Hazard assessment of marine pests in relation to Australian aquaculture industries

Executive Summary

Marine pests are known to be introduced or translocated by a variety of anthropogenic and natural vectors, including ballast water from commercial shipping, biofouling on a wide range of vessels, aquaculture operations, aquarium imports, marine debris and ocean current movements. The continuing encroachment of marine pests into new areas threatens biodiversity, natural resources, aquatic and human health, as well as specific industries dependent on the marine environment. This document outlines the results of an investigation into the hazards posed by Australian aquaculture as a vector for marine pests. However, it should be noted that aquaculture in Australia does not pose a significant threat of introducing new marine pests from overseas. Rather it is the potential for secondary transfer of marine pests that already occur in Australian waters that requires assessment.

A hazard analysis was conducted on representative marine aquaculture sectors in Australia following the Infection Modes and Effects Analysis (IMEA) method developed by Hayes in 2002. For this approach it must be recognised that hazard is not the same as risk and it is important to bear in mind that a hazard assessment is not the same as risk assessment. Hazard should be viewed as a latent capacity to engender harm, whereas risk is about the chances of that harm occurring. A consequence of this difference is that an entity may pose a substantial hazard, but at the same time present limited (or no) risk.

Five industry sectors were selected as representative case studies for the industry, including; edible oysters, pearl oysters, mussels, salmonids and southern bluefin tuna. Sectors were chosen according to the geographical range, production volume and economic value and to obtain a cross-section of a range of farming methods. The IMEA method involved four steps:

1. Breakdown of industry operations and infrastructure to specific components at the operator level

2. Determining which of eight of infection modes that could occur relative to each component.

3. Rating each component/infection mode combination from 1 – 10 according to;

a. Environmental suitability,

b. Likelihood of establishment, and

c. Likelihood of detection.

4. Calculation and evaluation of the Risk Priority Number (RPN) for each combination (0-1000).

Breakdowns of practices in each sector, identification of infection modes and scoring of each combination was undertaken through a series of meetings with industry representatives. Average RPNs for each sector were calculated and listed in order from highest to lowest scores. The top 50% of component/ infection mode combinations were employed in the interpretation of the relative level of hazard each sector may pose in terms of marine pest transfer. These interpretations were offset against the best available information on the regulatory framework in which each sector operates

In sectors where they occur, interstate transfers of stock are generally more stringently controlled than intrastate relocations and it is probably the latter that offer the greatest marine pest relocation hazard. This study has found the identification of gaps in relocation protocols difficult, as many sectors have state by state internal relocation guidelines that may be very similar, but nonetheless are a potential cause for confusion. The development of a single document for sector specific transfer protocols that covers all states would improve both awareness of issues elsewhere and the identification of gaps.

In most sectors, the measures in place to combat disease (depuration, emersion, freshwater/brine washes, scrutiny) are also likely to be effective barriers to marine pests. However, a higher level of pest risk awareness in some sectors/regions has led to creation of some pest specific protocols. This specifically relates to the mussel industry in Victoria, with measures developed by operators targeting the threat posed by the Pacific seastar (Asterias amurensis). There is a high level of awareness within the pearl oyster sector following the outbreak of black-striped mussel (Mytilopsis sallei) in Darwin Harbour. Finally, oyster farmers in NSW have measures in place to limit the spread of Pacific oysters (Crassostrea gigas). While these approaches are targeted to particular pest species in particular regions, they are likely to be similarly effective against other pests.

Intrastate movements of equipment and infrastructure present generally greater marine pest hazards than stock. Within edible oysters, sticks, rafts and racks present the largest marine pest hazard, while for mussels and pearl oysters, anchors, buoys and longlines presented a relatively high hazard. In the salmon and southern Bluefin tuna sectors, seacage infrastructure (nets, rings, ropes and anchors) present the largest marine pest relocation hazard. External and internal fouling and refuge infections present the majority of higher hazard infection modes, although others occur in specific instances (e.g. wood borers on sticks used in NSW oyster farming).

It must be remembered that the identification of a hazard does not necessarily mean that the risk of marine pest relocation exists, only that there is a potential.

The most effective control over marine pest risks would appear to be through development of pest management protocols for particular areas, similar to those operating in the Victorian mussel sector. Similarly, salmon farming in Tasmania is already divided into three management zones, albeit targeted to hygiene, but the effectiveness of this approach to pest risk management is worthy of further investigation. For sectors with a geographically small range, such as southern Bluefin tuna, the development of pest management protocols is currently unwarranted, but a greater awareness of marine pest risks and the need for development of protocols that cater for expansion of the sector to new areas is required.