Restoring the Vosso

What must be the most intensive and comprehensive salmon recovery programme on any river is to be launched on Norway's River Vosso.

The Norwegian Directorate of Nature Management has drawn up the rescue plan after a long-running study blamed the sustained failure of the river stock largely on salmon farming in fjords.

Stocks collapsed in 1988 and have not recovered although salmon are still present in the river due to escapes from farm pens and hatchery programmes. Vosso salmon genes are preserved in a live gene bank and the directorate plans to use its gene bank reserves, that can not be preserved indefinitely, to re-establish the pure Vosso strain.

The research looked at a series of possible contributory factors to the Vosso salmon's decline, including:

* Lowering of the Vosso lake (1989-1991).
* Road-building close to the river in the late 1980s.
* Acidification of water.
* Escaped farmed-fish spawning in the river (60 to 70 per cent of the catch in recent years has been escaped farm-fish).
* Sea-lice from fish-farms killing outward migrating smolt.
* The Evanger hydro-power station creating lower summer river temperatures and more acid water.

Of all these possible contributors, the report concluded that the most persistent overwhelming damage to stocks was caused by sea lice killing returning smolt and the escape of farmed salmon diluting what remained of the gene pool.

Earlier problems, such has acidity, have been resolved through better water quality. Fry survival from hatcheries in the upper river has been encouraging. But smolt still struggle to run the gauntlet of the salmon farms.

More recently conservationists have begun towing batches of smolt in special cages through the fjords, giving salmon farms a wide berth. Smolts are also being vaccinated against sea-lice attacks which research has shown is another significant aid to survival. Return rates have improved as a result.

Now the directorate is to consolidate the most successful initiatives in a programme that will re-introduced the Vosso gene. The programme has a two-pronged strategy aimed at both improving the quality and survival rates of Vosso salmon smolts and at lessening the damage caused by salmon farming.

Specifically the programme intends to:

* Establish production of 1.5 to 2m eggs a year in the gene-bank through increased breeding stock.
* Increase the capacity in the Vosso hatchery.
* Implant 1 to 2m "eyed ova" during wintertime.
* Release 200,000 to 400,000 one-summer fry.
* Establish a part of the upper river that has no natural run as a "living gene-bank".
* Release 100,000 to 200,000 smolt at different parts of the migration route, and with different treatment regimes against sea lice attacks.
* Establish a regime for marking all genetic material.

To limit sea lice attacks on smolt it intends to:

* Coordinate anti-sea lice treatments among all fish farmers.
* Control sea lice levels.
* Move some fish farms.
* Catch some of the smolt in river, and tow them out to sea (tests have shown this methods produces much higher return rates).

To limit escapes from fish farms it will pursue the following initiatives:

* Instigate better escape-prevention.
* Limit net fishing in fjords.
* Insist on the release of all wild fish (marked) and the culling of escaped fish.

It's good to see such a co-ordinated response. To succeed it will need the co-operation of powerful salmon farming interests with a view, perhaps, to a shrinkage or radical repositioning of salmon-farming in future. That commitment does not exist at present but if this initiative fails it could be the only answer. If the plan succeeds we may yet get the opportunity to fish for those magnificent Vosso salmon once more.

Material for this report was supplied to me by Riise Bjørn of Klæbu Sparebank in Norway who has been monitoring the Vosso programme for some time. He describes the Vosso as "a unique biological resource." I would second that.