The salmon population has plummeted in Dorset's River Frome, a new report suggests.

According to the latest figures in a fisheries report, the numbers of adult salmon that returned to the river in 2018 were at a 'worrying low'.

The Frome rises in the hills of west Dorset and flows east through Dorchester and to Wareham where it and the River Piddle flow into Poole Harbour via the Wareham Channel.

The 2018 Fisheries Research Review, published by the Game & Wildlife Conservation Trust (GWCT), shows that the very low number of smolts (young salmon) left the Frome in 2017 resulted in a poor run of grilse – salmon returning after a winter at sea.

Poor spawning will have a knock-on effect this year and next, it is said.

This result was predicted by the freshwater ecologists in the GWCT fisheries team, who are based at East Stoke, near Wareham.

Head of fisheries research Rasmus Lauridsen, who is currently on the River Frome tagging 10,00, said early winter 2015/16 was very warm and it is likely these high temperatures that affected 'recruitment'.

Poor recruitment from the 2015/16 spawning season was reported widely across much of England and Wales. Other rivers affected by this poor spawning season are likely to see the same effect on the number of returning adults in 2019 and 2020 as smolts from the River Frome and other chalk streams are generally a year younger than smolts from other rivers.

Research shows that larger salmon smolts survive better at sea than smaller smolts. It appears that a 16cm smolt is three to four times more likely to survive their marine migration compared with a 12cm smolt.

The fisheries team have had a successful year tagging sea trout as 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 over a five-year period.

David Mayhew, chairman of GWCT fisheries research steering committee, said: “A better understanding is urgently needed to protect this enigmatic species from bycatch in coastal nets and to preserve coastal areas of special importance to sea trout.”

The fisheries team have now started their annual tagging of 10,000 salmon and 3,000 trout parr to track their movements and life-history choices.

To support fisheries research visit gwct.org.uk/fishing/