SAVE OUR SCALES

Despite the government’s disinclination to take action, salmon populations need support – and the scientific proof should not be sneezed at, says Michael Wigan

It's time to listen to the boffins about risks to our salmon populations

Laws to protect salmon started in Scotland in the eleventh century, in England in the thirteenth. There has never been a lack of protective effort. Human pressure on the silver bounty started early and has never relented.

All governments forming environmental policies now say they follow science. In the case of salmon this is usually privately funded. The latest project in Scotland is the Missing Salmon Alliance, led by the Atlantic Salmon Trust. Its aim is to discover why fewer migrating salmon are returning.

Spanning seven rivers between Spey Bay and the Brora, researchers tagged 850 salmon smolts going downriver in spring 2019. They fitted acoustic tags. Journeys are logged passing acoustic receivers, of which 358 were anchored to fixed locations. During the 2019 spring migration over 15 million pings were recorded, the smolts passing arrays of receivers as they swam seawards.

Rightly, the project organisers believe that releasing information findings, even when only partial, keeps news rolling. Half the smolts never made it to salt water. They disappeared in their home rivers. That was more than expected, although such figures, and higher, had been found on some individual rivers previously.

As smolts hit saltwater they fanned out in the Outer Moray Firth. And they can shift. One swam 125 miles in a fortnight. This is a fish only inches long. Disappearances at sea were lower than forecasted. Early indications show that 15% were lost in the inshore zone.

The Missing Salmon Alliance is holding its breath about the meaning of these first results. Is river mortality due to river conditions, is it ‘part of life’, or is it predation?

Talk to river people and they will cite predation as the main culprit. If so, that would be good news. Predation can be addressed, given government willpower. Clinging to inaction, always the preference, may be harder if predation is proven to be hammering a species which is sometimes the backbone of remote local economies. It will be hard to duck issuing enough licenses to significantly reduce predators.

This research is all based on the east coast. This is where salmon river populations may have dwindled but are still in places robust, and things are less political. On the west coast there are too few wild smolts to tag and the inshore, packed with sea-lice from salmon farms, is likely to be their cemetery. The east coast is the right focus. The 2020 aim is to identify ‘likely suspects’ in freshwater predation.

Salmon recovery never lacks champions. A new theory has arisen about the usefulness of tree cover. If smolts are bigger and fitter they will dodge predation more successfully. Therefore river managers should enhance early life habitat to maximise smolt survival. Tree shade helps salmon in hotter summers and provides drop-down food for young fish. So planting upper catchments with trees to support fish is being mooted.

The theory sounds alright until you widen the frame. Iceland and northern Russia, the star contemporary salmon fishing locations, do not have forested catchments. Several of the world’s best rivers flow off granite shields in tundra where there isn’t a bush in sight, let alone a tree. On open land salmon are insect eaters, consumed as larvae, pupae and winged adults, of mosquitoes in the arctic to caddis and sedge in Scotland. Electro-fishing on northerly Scottish rivers shows bigger young salmon in open moorland, shrivelled ones in the shade.

The hot summer of 2018 revealed that young salmon have a method of coping with high temperatures in shrunken burns. Even water heating to 25°C does not necessarily kill them.

Conductivity study, analysing baseline rocks for invaluable elements like calcium, shows unexpected results. The worst-looking dribbling dirty streams, banks ploughed by cattle hooves, might have the best baseline rocks for prolific young salmon. Geology rules. Only recent research using electro-fishing has brought some of this to light. We may yawn at yet more science. I say, bring it on.

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The worst-looking dribbling dirty streams might have the best baseline rocks for prolific young salmon