Conservationists monitoring numbers on the River Frome in Dorset have counted their lowest numbers of the endangered fish on record.
An annual salmon count has uncovered a “catastrophic” collapse in the number of juveniles in one of the country’s most important rivers for the species.
Conservationists monitoring juvenile wild Atlantic salmon on the River Frome in Dorset normally aim to count and tag 10,000 during a four-week period in the summer but this year only managed a record low of 3,226. This follows a previous record low of 4,593 last year.
Will Beaumont, a senior research assistant Game and Wildlife Conservation Trust (GWCT), said: “Last year was the worst we’ve ever had, but this year has been catastrophic. This follows on from yet another year where we have seen a new record low number of adults returning from sea to spawn, confirming the continued steep decline of salmon in our rivers.”
Numbers of wild Atlantic salmon have crashed by about 80 per cent in the past 40 years. Rivers that had tens of thousands of salmon in the 1980s now only have a few hundred, and wild Atlantic salmon are classified as endangered in the UK. The species is on the International Union for Conservation of Nature Red List, along with elephants, pandas and polar bears.
In an attempt to identify the causes, the GWCT’s research team spends four weeks on the Frome in late summer catching, weighing, measuring and microchipping the juvenile salmon, known as parr, that hatched in spring.
Based at their river laboratory near Wareham, workers from the charity headed to a different section of the Frome every morning, trying to cover as much of the juvenile salmon habitat within the 20 mile-long river as possible. The count has taken place for the past 20 years.
Dylan Roberts, the head of fisheries at GWCT, said the record low counts were “alarming” and “if it continues, salmon could disappear from our UK rivers in the next 30 years”. He added: “It is also sadly reflective of what’s happening in other rivers in the UK and more widely in Europe. Almost all salmon rivers in England and Wales are classified as at risk by the government bodies.”
Roberts said the issues for salmon were “many and complex” as they were facing “much tougher conditions in the marine environment, where global warming and concerns over bycatch are posing serious threats”. He explained: “But if we are able to improve conditions in our rivers, and make sure they can grow fitter, larger and stronger and reproduce in greater numbers, they will stand a better chance, once they migrate to sea, of returning in larger numbers.”
Roberts said researchers had seen a “huge increase in the growth of algae between spring and autumn” on the Frome, which reduces oxygen levels in the water and smothers and kills off crucial habitats for juvenile salmon and the insects upon which they feed. “The algae grows excessively due to high levels of nutrients — nitrate and phosphate which are released into rivers from sewage, septic tank discharges and running off agricultural land,” he said.
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