Å®ÉúСÊÓƵ

SALMON FARMERS in Britain can continue to treat their fish with the
highly toxic chemical, dichlorvos, despite the government’s undertaking
to reduce inputs of this chemical to the marine environment. The Ministry
of Agriculture, Fisheries and Food, has extended the licence for the organophosphorous
pesticide Aquaguard (formerly Nuvan) for a further two years.

Aquaguard is effective against sea lice, the most important parasites
of farmed salmon. Fish packed into sea cages at high densities are prone
to devastating infestations. As Nuvan, the pesticide was notorious as the
cause of the deaths of marine organisms living near salmon cages, in particular
in Scottish sea lochs where cages have proliferated in recent years. Nuvan
was also linked with the enormous increase in cataracts in wild salmon (New
Å®ÉúСÊÓƵ, Science, 26 August 1989).

Dichlorvos is one of the polluting chemicals that the North Sea Conference
wants controlled, and the government has agreed to cut inputs by half by
1995. ‘Giving the product a licence for another two years runs counter to
the government’s commitment to cut down,’ said Alison Ross of the Marine
Conservation Society. ‘The ministry should give a clearer message that reductions
are necessary, which would provide a greater incentive to find alternatives,’
she said. ‘The ministry appears to be giving the industry as much leeway
as it can credibly afford to do.’

Studies are under way to find new ways to control sea lice. Trials with
‘cleaner fish’ which live in the cages alongside the salmon and eat the
lice hold promise (New Å®ÉúСÊÓƵ, Science, 21 October 1989). A search for
less damaging chemicals is also in progress.

Conservationists believe that prevention of disease is a better strategy
than treatment after the event. ‘Maybe the industry needs to rethink the
way it is run,’ suggests Ross. ‘If the industry can’t find a solution to
the disease problem then maybe it should think about a preventative approach.’