Shooting and Fishing: They nip out via any handy hole. swim out to sea, chase a few prawns, then go home

One of the big beefs about salmon farming is that smolts, juvenile salmon, get out of their cages and mess up the survival prospects of their wild cousins. They nip out through any handy hole in the cages, swim out to sea, chase a few prawns in the Atlantic and then come home.

Once in the spawning areas there is no telling who is fertilising whose eggs. The resulting progeny will be flabby and hopeless, prone to parasites and disease which they then pass on. That's the big worry. And, as if that isn't bad enough, the feed thrown to the smolts tends to go through the bottom of the cages and sea trout sit around underneath getting fat instead of going to sea.

(Rather embarrassingly, on the subject of smolt escapes, there has been one in Loch Arienas this summer – embarrassing because Andrew Wallace, director of two wild fish lobby groups in Scotland, is also a director of the estate that gave the smolt breeder a lease on Arienas.)

While I may make sport of these things, the WWF, no less, has also raised serious doubts about putting smolt cages in lochs shared with wild fish. Its Aquaculture Stewardship Council (ASQ) is proposing, under something called the Salmon Aquaculture Dialogue (SAD; I should say), to refuse its certification for smolt cages in waters shared with wild salmon or sea trout. This means that for salmon farms to supply supermarkets that favour a certification logo as a marketing tool, they will have to put their smolts in escape-proof ponds on shore.

My bet is that the salmon farming industry will be screaming blue murder about this. There are around 17 million smolts in cages and pens, many in waters shared with wild fish.

The alternative is Recirculating Aquaculture Systems (RAS) – onshore ponds with a continuous flow of recirculating clean water. The other option is to rear smolts in freshwater lochs like Loch Laggan – Loch Bogle in Monarch of the Glen – where there are no salmon or sea trout.

Fortunately, the Scottish salmon industry is awash with cash just now, thanks to demand for its wares created by the loss of Chilean salmon production through disease. So a switch to RAS may be expensive but not fatal.

The flaw in all this is that the proposal to certify only clean and green smolt production is a proposal, not a done deal. So you really need to say your piece, because the Scottish Government, in thrall to the industry, probably won't.

Visit www.worldwildlife.org/what/globalmarkets/aquaculture/dialogues-salmon.html