Latest News, Wildlife | Posted: Tuesday, August 25th, 2020 at 12:35 pm | return to news

Fall of salmon population recorded in Dorset's River Frome

Young salmon leaving the river for the sea at Poole Harbour two years ago were the smallest ever recorded by the Game & Wildlife Conservation Trust, (GWCT) which could have led to the reduction in adult salmon on the River Frome.

In-river range testing of acoustic tags
In-river range testing of acoustic tags

And according to the trust’s Fisheries Research Review, this decline shows no signs of abating.

It had been hoped that a good number of smolts (young salmon leaving the river for their marine journey) in 2018 would boost these numbers, but far fewer returned to the river than expected.

Previous research by the GWCT has shown that larger smolts are more than three times more likely to return from the sea than smaller ones. The worryingly low number of smolts that left the river in 2017 will also have had a major impact.

Despite these alarming findings, the fisheries ecologists at East Stoke, near Wareham are working hard to understand the declines. 2019 and 2020 have been very busy years, beginning with smolt monitoring on the River Frome, 24 hours a day for six weeks.

The fisheries team enlisted their families to ensure that the River Frome was perhaps the only river in Britain to have full monitoring through lockdown. This dedication avoids a two-year gap in the data, as this year’s smolt will be monitored when they return as adults over the next two years.

Much of this work is part of SAMARCH, a multi-million-pound project that will provide crucial evidence to strengthen the management and protection of salmon and sea trout at sea from 2017 to 2022.

David Mayhew, chairman of GWCT fisheries research steering committee, said, “Our fisheries team spent more time in the field last year than probably any other year in the last 10 years. Furthermore, two of our PhD students, Jessica Marsh and Jessica Picken, submitted their theses on the importance of instream vegetation for salmonids and the effect of low flows on salmonid ecosystems, respectively.”

It is hoped that Jessica Marsh’s work will offer rare optimism for salmon numbers.

Rasmus Lauridsen, head of GWCT Fisheries Research, is encouraged by the findings. He said, “This work illustrates how important juvenile freshwater habitat is. It could provide us with a management tool to increase not only the production of juvenile salmon but also their growth rate in lowland rivers.”

Both PhD studies are featured in the report, along with two new studies. Dan Osmond, undertaking a PhD with Cardiff University and the University of Exeter, is examining the impact of metal pollution in British rivers, notably on brown trout, and Olivia Simmonds is working on her PhD study with Bournemouth University, exploring the factors that determine when salmon migrate.

The review can be downloaded for free at www.gwct.org.uk/fisheriesreport.

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