River's salmon numbers at record low

Numbers of salmon in a river have fallen to their lowest in 40 years, conservationists have said.

The Game and Wildlife Conservation Trust (GWCT) tagged and weighed about 10,000 salmon in the River Frome in Dorset last year, before tagging juveniles as they migrate out to sea.

Each year researchers aim to catch and tag about 10,000 but this year's survey managed less than 4,000.

The trust said it showed the "continued steep decline" of salmon in rivers.

Researchers have been tagging and surveying salmon in the Frome since 2005.

The team catch and tag the juveniles which are are living and growing in the river each autumn.

The individual salmon are recorded by tag readers and fish traps in the river, as they migrate out to sea the following spring as year-old fish known as smolts.

When the survivors return to the river after having spent a year or two feeding in the North Atlantic, they are again recorded as they pass the readers in the river.

The trust's records show in the 1970s and 80s, about 15-20% of the salmon that went to sea would return as adults but that figure was now just 4-5%.

In 2023, an estimated 443 salmon returned to the river to spawn, compared to up to 4,000 a year in the 1980s

Senior research assistant Will Beaumont said 2024's results had been "the worst we’ve ever had".

“We have failed to hit 10,000 parr [juveniles] in the past on several occasions but usually it’s not this far off," he continued.

The previous record low of 4,988 in 2016 was attributed to rivers being too warm in winter and too low in spring.

The trust said a number of factors were thought to be behind the decline of wild Atlantic salmon including run-off from agricultural land and climate change causing warming seas and rivers.

Dylan Roberts, GWCT’s head of fisheries, said: “We know that excessive sediment in rivers caused by run-off from agricultural land reduces the survival of salmon and trout eggs and the Frome has a lot of sediment in the gravel."

He highlighted the effect nutrients from sewage treatment discharge and septic tanks can have on river water.

"This causes excessive growth of algae which suffocates the riverbed, shades and reduces the growth of plants, like water crowfoot, that provide crucial habitats for juvenile salmon and the insects they feed on," he continued.

Source: GWCT

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