Australia: Unwanted marine pest identified

The Department of Fisheries will begin survey work next week to confirm the presence and check the extent of a marine pest, which has not previously been found in WA.

This green seaweed, formally known as Codium fragile ssp. tomentosoides, has recently been identified in a sample of macroalga taken at Albany’s Town Jetty.

Experts agree this particular seaweed is difficult to tell apart from some other species of Codium, which are not defined as marine pests. It has previously only been found in marine environments in South Eastern Australia and its presence at the Town Jetty makes it difficult to be sure how it was transferred to Princess Royal Harbour.

Department of Fisheries Biosecurity Management Officer Dr Stephanie Turner said the unwanted seaweed had the potential to smother shellfish (by preventing shell opening), foul nets and be a nuisance to commercial fishers, and potentially produce unpleasant odours if masses were to accumulate and rot on beaches.

“Since it was identified in the sample sent to a specialist taxonomist, the Department of Fisheries has taken steps under the National System for the Prevention and Management of Marine Pest Incursions to notify relevant government agencies and stakeholders of the test results to help work up a plan of action to deal with it,” Dr Turner said.

“This marine pest has earned the nickname as the ‘oyster thief’ in the US for its tendency to smother oyster beds, but it can also smother mussels and scallops.

“It could have been translocated to Albany a number of ways, but from its location on the jetty, it is hard to know exactly how that happened. We will undertake field work from next Monday (16 June) to collect important information that will help us understand how widely it is distributed.”

Dr Turner said the specimen identified was fertile so the early investigation work would be vital in mapping out options for responding to this marine pest incursion.

“Codium fragile ssp. tomentosoides is a large dark green macroalga with one to several, thick and upright branches which can be 15 to 20 centimetres high,” she said.

“As a result it has attracted the description “dead man’s fingers” and it is listed as a marine pest, because of its invasiveness and for the impacts it’s had on shellfish farms in the northwest Atlantic.

“In Australia it is reported to settle on native algae and shellfish and foul commercial fishing nets, but in large part it is a marine pest issue that needs to be assessed further and there is no need for any alarm as it is not a problem for the wider community.”

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Australia: Unwanted marine pest identified