Gone fishing for sea lice

December 14, 2001

Scientists have isolated the true scent of salmon in a bid to trap a major fish-farming pest.

The light, sweet, mushroomy fragrance comes from key signalling chemicals produced by the fish. These chemicals have been shown to be enticing to parasitic sea lice.

The experts hope to turn that chemical allure into a fatal attraction by incorporating the substance in traps for the tiny crustaceans.

Project head Jenny Mordue, reader in zoology at Aberdeen University, said the technique could prove an effective and environmentally friendly alternative to veterinary medicines.

Sea lice are one of the most significant blights on salmon farming, costing the United Kingdom's industry £30 million a year.

The 1.5cm long crustaceans use semiochemicals given off by the fish to recognise their hosts. They eat into their flesh, causing skin lesions and even death.

A number of drugs have been developed to protect salmon from sea lice. However, these are regulated as they can affect other crustaceans and, if misused, can allow the pests to build resistance.

Dr Mordue's team included collaborators at the Institute of Arable Crops Research, Rothams-ted, Nottingham University and AgriSense, a com-pany based in Pontypridd.

They extracted a variety of chemicals from clean water through which the salmon had swum, using a technique developed by IACR chemists.

These were tested for their biological activity. One was found to have a great effect on sea-louse behaviour. The compound is similar to those used by insects to signal to one another.

Dr Mordue plans a trial in a sea-loch estuary using traps to snare the pests.

The research is to be published in the journal Pest Management Science . A patent application on the chemical has been made.

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