Problem Statement: Darwin is the largest port on the tropical northern Australian coast. One of Darwin Harbour’s three marinas, Frances Bay Marina, is the base of the pearl and northern prawn fishing fleets, which are major export earners driving the Australian economy. On March 27th 1999, divers in Cullen Bay Marina within Darwin harbour discovered dense aggregations (23,650 individuals/m²) of a thin-shelled bivalve “mussel” that had never before been seen in this area.

Methods: The “mussels” were immediately sent to an experienced taxonomist based at the Museum and Art Gallery of the Northern Territory in Darwin and were identified as Congeria (Mytilopsis) sallei. It was confirmed that Mytilopsis sallei, as it was named in the marine pest literature, previously did not occur in Australia.

Outcomes and Impacts:  M. sallei is a recognized invasive species that can breed very rapidly and cause massive fouling on wharves and marinas, seawater systems, and pearl and aquaculture facilities. By April 1st, the Northern Territory Government declared a state of Natural Disaster, closed and quarantined all three marinas of Darwin Harbour, and instigated an eradication campaign. The M. sallei populations infesting the marinas were effectively killed through chemical treatments, and all vessels that had recently left the marinas (including the complete northern Australian prawn fleet) were checked. As of November 2007 no further live M. sallei have been found in Darwin Harbour or anywhere else along the Australian coastline. Efficient monitoring of the sea traffic helped to detect subsequent incursions of these "mussels", e.g. on the hulls of boats caught illegally fishing in Australia waters, eliminating the risk of new invasions of this notorious pest species.

Lessons: Access to confident and experienced taxonomic specialists can be vital to implementing fast, cost-effective invasive species management plans.