GOLDEN AGE OF FISH

Despite most anglers being more concerned by this season’s catch of wild salmon, Michael Wigan can’t help being fascinated by the science behind historic run cycles

Michael Wigan is fascinated by historic run cycles

He who lives longest knows most, they say. In the case of wild salmon populations it would help to live a thousand years. Researchers in Oregon have got round this ageing problem by analysing core samples over 2,200 years. A wave-like pattern of west coast Pacific salmon, troughing then surging back, can be seen in 20 to 30-year abundance cycles.

From 1500 and from 1700 runs fell, and then collapsed again in the Little Ice Age of the early 1800s. Middle periods had been good. The 1950s, like for Atlantic salmon in a different ocean, were poor. This new decade here at home may witness a grilse cycle ending and a salmon one beginning. Older salmon and grilse cycles never peak together.

The Pacific north-west is far away, but ocean currents and oceanic temperatures are not. In the 1980s Tony George, a philosophy graduate from Wolverhampton, did brilliant work on salmon cycles, sifting through mountainous sets of records, and was published in Trout & Salmon. His conclusions we should perhaps remember at a time of alleged crisis.

Tony George started in the late 1700s with market records, and later with train and steamship freight records carrying Scottish salmon to English markets. One standout period was the dearth of salmon following 1888. It lasted 60 years for grilse and 35 years for salmon. From the 1920s as salmon started to flourish again tonnages ferried to England sharply rose. Then came the golden period commencing in 1957. An isolated dismal total Scottish rod catch of 48,000 in 1976, nearly as bad as the ghastly 37,000 in 2018, owed to a drought summer.

Tony George identifies two constant caveats. England, always prone to drought and high water abstraction, is different. The Tweed, with complex migrations, is another case apart.

From studying ocean and climate changes he understands that the Arctic and sub-Arctic, where our salmon spend the winter, change more dramatically than the tropics. We see that now with the ice-cap thinning. Salmon’s food supply shifts north or south following Atlantic temperature bands. In all the variables he stresses this point: more southerly-found feed increases the runs of grilse and shrinks the number of salmon. Put another way, the fish accumulate weight for successful breeding without travelling so far, therefore return earlier. The magic high-catches of the late fifties coincided with the warmest ocean temperature for 1,000 years, so grilse fattened fast and returned in multitudes.

It coincided, too, with the mid-sixties ‘gadoid outburst’, producing vast numbers of the gadoids such as cod and haddock. Fishing boats were even dragged under, nets brimming-over with haddock, whiting and cod. In the sea, salmon are like any other fish, feeding to breed.

Most anglers are less interested in cycles of salmon abundance over centuries than what portends this season. Citing anguished laments about the disappearance of salmon in the 1920s, as Tony George does, is not of keen interest when loading the car at dawn tomorrow.

2020 trends suggest we are moving out of a grilse cycle into a salmon, earlierrunning, fish period. The fish counter on the Helmsdale recorded a far bigger spring migration in 2019 followed by a shrunken grilse cycle. For those lamenting fewer ‘lippy’ grilse zinging round the pool, consider, the springer is bigger and available for catching for longer.

Another of Tony George’s themes is distinguishing grilse from salmon. Scale reading is the only true determinant. Today’s assumption is that grilse weigh 6lb, tops.

Mr George produced a table showing that in the sixties and early seventies nearly all 6-10lb fish caught in the nets were grilse, not salmon. They fattened quickly on a munificent sea larder and developed ova and sperm. Past records relying on weights, he says, frequently mis-described grilse as salmon.

There may be new determinants for salmon abundance but biological run cycles tend to endure.

“Anglers are less interested in salmon abundance over centuries than what portends this season