A foul tale of marine invasions

Feral Herald |
Biofouling on a vessel hull. Photo: Robyn Draheim (Creative Commons licence)

After vociferous community protest, the Federal Government recently banned the 142 metre Abel Tasman ‘supertrawler’ from fishing in Australian waters while it investigates the environmental impacts of taking 18,000 tonnes of small fish from waters around southern Australia.

But there is potentially a much greater risk that hasn’t received any mention. Of concern for Australians should be not only the wildlife removed from our seas but the wildlife released into them.

The Abel Tasman, which sailed from Holland and has fished in West African waters, may have exemplary vessel hygiene – I have no way of knowing – but fishing vessels in general are liable to biofouling, the accumulation of marine organisms such as barnacles and algae on their submerged parts and fishing gear. A New Zealand survey reported by Sinner and colleagues (2000) found 16% of fishing vessels hosting the highly invasive Japanese seaweed (Undaria pinnatifida). It can form dense forests on sheltered reefs and was introduced to Tasmanian waters probably via fishing nets and anchors. A Russian vessel fishing in New Zealand waters that had come from the Black Sea had 90 tonnes of biofouling on its hull (reported by Hay and Dodghun 1997).

Biofouling on a boat hull. Photo: Graham_B (Creative Commons licence).

Biofouling is probably the major cause of marine invasions globally. Up to about two-thirds of the 1781 marine organisms globally known to have established outside their range are thought to have arrived as biofouling of vessels or equipment. The other major form of dispersal is via ballast water.

About 250 non-indigenous species are known to have already established in Australian waters. Another 230 species are suspected to be non-indigenous. An estimated three to four new species establish each year.

A risk assessment by Chad Hewitt and colleagues (2011) for the Australian Government identified an additional 56 species with a high probability of arriving in Australian waters via biofouling with the potential to cause moderate to extreme impacts.

Biofouling is one of Australia’s most neglected conservation issues. Fishers are required to comply with fishing quotas but compliance with biofouling guidelines is voluntary only. One fishing operation can cause local impacts by overfishing but potentially catastrophic ecosystem-wide impacts if they fail to clean their gear or vessel. Marine ecosystems can usually recover from overfishing but once an invasive species is established, it is mostly too late to prevent damage. Eradication is usually not feasible.

Voluntary compliance with biofouling guidelines is all that is asked of most vessels arriving in Australian waters or traveling between ports. Last year, the Federal Government sought public comment on a proposal to introduce mandatory biofouling measures. They are still considering their response. The draft Biosecurity Bill currently out for public comment does not mention biofouling, although, encouragingly, it does propose national regulation of ballast water disposal.

About 15,000 vessels each year arrive in Australian waters from overseas, about 90% of which are commercial vessels. The greatest risks are with slower moving vessels, with vessels that have long spells in port and if vessel owners are slack with maintenance (a major risk with recreational vessels). Because commercial vessels travel rapidly, they are thought to pose less risk than slower fishing vessels and yachts. But Oliver Floerl and Ashley Coutts (2009) raised the spectre of a wave of biofouling invasions from commercial ships due to the Global Financial Crisis (GFC).

Reduced trade volumes due to the GFC would have had environmental benefits by slowing the introduction of invasive species, which arrive either as traded goods or hitchhiking with goods or on vessels. But while unprecedented numbers of merchant ships languished for months in ports, they were accumulating “diverse and extensive assemblages of marine biofouling species”. The submerged surface area of a large vessel may exceed 10,000m2 and accumulate more than 20 tonnes of attached organisms. As the GFC has eased and trade picked up, ships are likely to be spreading these hangers-on far and wide. Dry docks are too few in number to have coped with all the vessels requiring hull scraping and smaller companies may not have been able to afford it after the business downturn.

There is a dire need for regulation in Australia and globally to mandate vessel hygiene. It shouldn’t be up to the good will of fishers, yachties and traders to keep their vessels free from dangerous hitchhikers.

biofouling barnacles
Barnacles are common biofouling organisms. Photo: ecotist (Creative Commons licence)


Floerl O, Coutts A. 2009. Potential ramifications of the global economic crisis on human-mediated dispersal of marine non-indigenous species. Marine Pollution Bulletin. 58 (11): 1595-1598.

Hay C, Dodgshun J. 1997. Ecosystem transplant? The case of the Yefim Gorbenko. Seafood New Zealand, May 1997, 13-14.

Hewitt C, Campbell M, Coutts A, Dahlstrom A, Shields D, Valentine J. 2011. Species Biofouling Risk Assessment, Report for the Department of Agriculture, Fisheries and Forestry, National Centre for Marine Conservation & Resource Sustainability, Australian Maritime College, University of Tasmania and Aquenal Pty Ltd.

Sinner J, Forrest B, Taylor M, Dodgshun T, Brown S, Gibbs W. 2000. Options for a National Pest Management Strategy for the Asian Kelp Undaria: Technical Report. Prepared for the Ministry of Fisheries.

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