Calendar An icon of a desk calendar. Cancel An icon of a circle with a diagonal line across. Caret An icon of a block arrow pointing to the right. Email An icon of a paper envelope. Facebook An icon of the Facebook "f" mark. Google An icon of the Google "G" mark. Linked In An icon of the Linked In "in" mark. Logout An icon representing logout. Profile An icon that resembles human head and shoulders. Telephone An icon of a traditional telephone receiver. Tick An icon of a tick mark. Is Public An icon of a human eye and eyelashes. Is Not Public An icon of a human eye and eyelashes with a diagonal line through it. Pause Icon A two-lined pause icon for stopping interactions. Quote Mark A opening quote mark. Quote Mark A closing quote mark. Arrow An icon of an arrow. Folder An icon of a paper folder. Breaking An icon of an exclamation mark on a circular background. Camera An icon of a digital camera. Caret An icon of a caret arrow. Clock An icon of a clock face. Close An icon of the an X shape. Close Icon An icon used to represent where to interact to collapse or dismiss a component Comment An icon of a speech bubble. Comments An icon of a speech bubble, denoting user comments. Comments An icon of a speech bubble, denoting user comments. Ellipsis An icon of 3 horizontal dots. Envelope An icon of a paper envelope. Facebook An icon of a facebook f logo. Camera An icon of a digital camera. Home An icon of a house. Instagram An icon of the Instagram logo. LinkedIn An icon of the LinkedIn logo. Magnifying Glass An icon of a magnifying glass. Search Icon A magnifying glass icon that is used to represent the function of searching. Menu An icon of 3 horizontal lines. Hamburger Menu Icon An icon used to represent a collapsed menu. Next An icon of an arrow pointing to the right. Notice An explanation mark centred inside a circle. Previous An icon of an arrow pointing to the left. Rating An icon of a star. Tag An icon of a tag. Twitter An icon of the Twitter logo. Video Camera An icon of a video camera shape. Speech Bubble Icon A icon displaying a speech bubble WhatsApp An icon of the WhatsApp logo. Information An icon of an information logo. Plus A mathematical 'plus' symbol. Duration An icon indicating Time. Success Tick An icon of a green tick. Success Tick Timeout An icon of a greyed out success tick. Loading Spinner An icon of a loading spinner. Facebook Messenger An icon of the facebook messenger app logo. Facebook An icon of a facebook f logo. Facebook Messenger An icon of the Twitter app logo. LinkedIn An icon of the LinkedIn logo. WhatsApp Messenger An icon of the Whatsapp messenger app logo. Email An icon of an mail envelope. Copy link A decentered black square over a white square.

Spey study shows climate change and human exploitation to blame for Atlantic salmon decline

atlantic salmon
The study took place at Loch Insh. Picture by Chris Conroy, Atlantic Salmon Trust.

Research has revealed that an abrupt change in climate conditions about 800 years ago and subsequent human exploitation in the North Atlantic played a role in the decline of Atlantic salmon populations returning to rivers.

The study by Southampton University and the British Geological Survey was carried out in Loch Insh.

Findings point to large-scale changes in the marine habitat brought on by a transition from a warm to a cold climate and what is now known as the Little Ice Age (circa 1300–1850), corresponding with decline in salmon in the River Spey.

Took samples from the loch

For the study, scientists took core samples from the loch, collecting and measuring marine derived nutrients (MDNs), which give an understanding of the historic population levels of salmon.

The researchers used control lakes with no exposure to salmon to determine and compare background nutrient levels.

As well as this, they also examined a 150-year record of net catch data from the lower Spey to help calibrate the MDN record, with fluctuations in numbers of returning salmon caught in the nets.

Salmon fishing remains popular. Picture by Kenny Elrick.

Lead author, David Sear said: “These results can help us understand some of the controls on salmon populations prior to and during major human exploitation.

“Our study shows that historically, beavers, common in Scotland hundreds of years ago, do not appear to have significantly impacted salmon numbers.

“This is very relevant today, as the animals are being reintroduced to UK rivers and a debate continues about their potential impact on migratory species like salmon.”

Climate change ‘makes it very relevant’

Co-author, Melanie Leng of the British Geological Survey said: “This research benefited from state-of-the-art geochemistry which enabled us to fingerprint salmon abundance over hundreds of years.

“We show that climate has been an important influence of salmon numbers, which is very relevant today due to the speed of climate change.”

This study, published in the international journal The Holocene, is the first to use MDNs to measure Atlantic salmon, with the method previously being used for Pacific salmon in northwest USA and Canada.

Conversation