Over the past couple of decades, while fishery scientists have been demonstrating that salmon hatcheries are a wasteful way of spending money, one voice has stood out to proclaim the opposite point-of-view: Peter Gray. Since parting company with the Environment Agency in Northumbria, for whom he ran the Kielder hatchery for 27 years, he has travelled widely, evangelically and enthusiastically telling audiences of salmon anglers that the excellent Tyne salmon runs are almost 100% because of his hatchery. Of course, his audiences go home convinced that the salmon populations of their rivers will never be healthy unless they too have a hatchery like Kielder. I once heard Mr Gray give his most convincing talk, but he progressed so rapidly that it was impossible to scrutinise the statistics he used. We must, therefore, be grateful to Medlar Press for publishing his arguments in favour of the widespread use of salmon hatcheries, for this enables us to examine more closely Mr Gray’s arguments. Space prevents me discussing them all.

By 1959, salmon and sea trout could no longer run the Tyne because of gross pollution between Hexham and the sea. Slowly the sources of pollution were cleaned up and adults of both species (together with another form of brown trout known as ‘slob trout’) were able to pass upstream and spawn. So from the mid 1960s the populations of both species increased, to a peak annual catch of salmon of between 3000 and 4000 and of sea trout to between 1500 and 2500 (in the years 2004 to 2008).

It was during this period (in the late 1970s) that the Kielder reservoir dam was constructed, putting the headwaters of the North Tyne beneath a 200 square mile lake, thereby destroying miles of salmon spawning and nursery stream. The Kielder hatchery was built to compensate for this, and during his time there Mr Gray and his assistants stocked over 8.5 million salmon into the river, mostly as parr. It was the stocking of this huge number of salmon parr, Mr Gray insists, that led to the great recovery of the river. However, rod catches (the index used to monitor the salmon runs, for the Tyne has no fish-counters) indicated that, before the hatchery was established in 1978-9, salmon had already returned with signs of a slowly increasing population. The big increase did occur after the hatchery had been operating: the catch exceeding 1,000 for the first time in 1987, 2,000 in 2000, and 4,000 in 2004. But was the hatchery in whole the reason?

It is impossible to say that the increase of the Tyne’s salmon population was mainly or entirely the result of the hatchery unless one knows how much hatchery salmon contributed to the next spawning population. And to do this we need data on the survival of hatchery reared salmon. This is usually obtained by tagging. Tagging was carried on a large sample of parr up to 2000, but Mr Gray does not give us any data from this work other than stating that, “The report’s [by the EA into the Kielder hatchery] conclusion that in the first six years only 20% of spawners were stocked fish is really quite ridiculous.” He argues that tagged fish may have been overlooked by fishermen.

This, alas, is a common trait amongst anglers whose preconceived ideas are shown to be incorrect. Go into denial!

What Mr Gray did do is look elsewhere for a conveniently high survival rate of farmed salmon to use in his calculations of the Tyne hatchery success, and that he found in Ireland. Using data from the Irish National Salmon Commission (1980-2002), he argued that the survival of hatchery salmon, released in selected rivers as smolts, “averaged 5% or better”, but that the survival rate of wild smolts had plummeted to similar levels. It is true that adult wild salmon numbers fell through the 1990s to 2003 because of dreadful feeding out in the Atlantic, but had Mr Gray extended his graph to 2003 (the data are there in the Report) he would have shown that 8% of wild Irish smolts returned as adult salmon, whilst farmed smolt survival was only 3%. Figures are not available for more recent years (when sea-survival has been much higher), but I wager that the gap was even greater.

However, that is not the point here. Mr Gray considers Irish statistics as being also reliable for Tyne analysis. However they are not:

• Most of the Irish rivers are very short, and/or their hatcheries are close to the tide, so that both wild and hatchery smolts can be in the sea within a few hours. In contrast, both South and North Tyne are long rivers, so that smolts must, for example, run the risk of predation by goosanders and cormorants for several days as they head off to sea.

• The Irish smolts then head north for roughly 500 miles to feed on the Faroe Banks until the following spring, when the vast majority return as one sea-winter grilse. In contrast, the Tyne fish also go to the Faroe Banks for their first winter, but then probably over 50% of them head 1,000 miles west, around Iceland and southern Greenland, to feed in the Davis Strait. After a winter in the west Atlantic between 40 and 50% of Tyne salmon return as two sea-winter fish (EA Report for 2010).

So using Irish data for sea survival for Tyne smolts is completely invalid.

He might have been better to use the perfectly accurate statistics from the Spey Board, for the Spey is closer to the Tyne in its salmon stocks than Ireland. The Board showed that in 2008-9 only 0.5% of hatchery raised salmon returned to the river. Extrapolating from this, in 2009, £120,000 spent on the Spey hatcheries would have produced only about 40 of the 8626 salmon caught that year! Had we had statistics from the Tyne in recent years, it is certain that its hatchery too would have been proved an irrelevant waste of money.

Another important point. In the calculations in which he attempts to demonstrate the virtue of hatchery over wild spawning he states that, “we assume half of them [wild adult salmon] ... were female.” He also states that, “As Liverpool University has found, older males can produce sperm that is dead or has poor mobility. If these males are competing when females are shedding eggs the ova may not be fertilised. If we use to correct procedures in a hatchery, however, we get nearly 100% fertilisation.”

However, it was a study – also by Liverpool University – that first demonstrated how sexually-mature male parr join adult males to attain nearly 100% fertilisation in wild salmon. Most if not all of these male parr die and do not go to sea as smolts. Thus the sex ratio of returning salmon is heavily weighted in favour of hens in the ratio of 60-70% female, 30-40% male. Thus, Mr Gray’s calculation of the number of eggs produced by wild salmon is significantly an underestimate.

Mr Gray has long been aware of one other major criticism, that the sea trout stocks increased simultaneously with the Tyne salmon yet without stocking. He argues that the sea trout increase was because brown trout produced the smolts that came back as sea trout (in which case the sea trout population would have bounced back more quickly than it did). He then argues that the numbers of both species increased in parallel because people increasingly fished for salmon as the salmon increased and caught sea trout accidentally as well. No one fished specially for sea trout on the Tyne, he suggests. Well, some of us did fish specially for sea trout (and slob trout) on the South Tyne in the 1980s, and we witnessed the increase of that species.

Finally, Mr Gray argues that, if we had hatcheries on many other rivers (he cites the Mersey as one, but not the Wear) we would be rewarded as was the Tyne. Not so. North and South Tynes, above their confluence, were perfect salmon and trout water through the years of pollution. It was just that the fish couldn’t swim through the filth. So, too, was the River Wear above Sunderland, that now has a great run of sea trout and salmon, sans hatchery. This is not the case with the Mersey. Since 2000 salmon have been running the Mersey in increasing numbers, and in the river above Stockport parr are now common. However the other tributaries, notably the biggest branch of the Mersey, the Irwell, cannot be reached by salmon because of impassable weirs. Above the weirs, the headwaters are now perfect, and when fish passes are put in position the Mersey will once again be an important salmon river. A hatchery is not needed. The money should instead be spent on fish passes!