Wild salmon conservation study guides path to restoring endangered native species

A new study in collaboration between the River Carron Conservation Association (RCCA) and the Institute for Biodiversity and Freshwater Conservation at UHI Inverness offers one of the most comprehensive investigations of conservation stocking of wild salmon in the United Kingdom.

Wild salmon populations in Scotland, now classified as ‘endangered’ on the International Union for Conservation of Nature Red List, have declined to such an extent that conservation stocking may, in some rivers, be the only option available to prevent the complete loss of these threatened populations. 

Well-monitored studies are therefore essential to maximise the long-term success of conservation programmes and establishing best practices to eliminate the potential genetic risks and ecological impacts traditionally associated with stocking.

The report demonstrates that fish stocked as eggs or juveniles survive to return as adults and in some years account for over 50% of the rod catch. Importantly, the study also provides crucial insights into ecologically sound methods for mitigating population decline this way and, in some cases, restoring the DNA integrity of wild populations.

The report draws from a rich archive of recently analysed genetic material and other data, collected over three decades by the RCCA’s award-winning scientist Bob Kindness, to accurately differentiate between wild-spawned and stocked salmon across multiple generations.

Following her analysis of the material, Dr Victoria Pritchard from the Institute for Biodiversity and Freshwater Conservation (IBFC) recently presented her report at an event in Edinburgh to share the second phase of DNA research. The event offered insight into the future management of wild salmon stocks and Bob Kindness gave an overview of the gathering of the rich archive of genetic material over the last 30 years.

Among the learnings, the study reveals that by breeding from wild-caught fish in the hatchery for a single season, rather than retaining females in captivity for multiple breeding cycles, it is possible to mitigate the risks to long-term genetic health associated with captive broodstock programmes. It also demonstrates that fish released at the Autumn (late) fry stage exhibit significantly higher survival rates compared to those released at different life stages.

“Before the Carron Conservation Programme, salmon stocks had dropped so low that the native fish faced real risk of extinction,” said Bob Kindness. “Once the programme was underway, a clear correlation emerged between the number of fish stocked and the number returning as adults. The resulting historically high rod catches were a testament to years of dedication and effort—an immensely rewarding outcome for me, as someone with a passion for the King of Fish.”

As expected, genetic material from Norwegian strains, introduced by commercial aquaculture escapees, was detected in both wild-spawning and captive broodstocks. However, the RCCA stocking programme does not appear to be increasing the level of Norwegian DNA beyond what would occur naturally in a wild-spawning scenario.

Moreover, the study highlights a strategy that could actively reduce Norwegian ancestry in the wild population. Incorporating fast-turnaround genetic testing into conservation stocking programmes could enable selectively avoiding breeding from genetically compromised fish. While this approach may not yet be fully practical, it represents a critical step toward best-practice conservation protocols for mitigating Norwegian aquaculture introgression in wild salmon populations.

These findings underscore the need for collaboration between salmon conservation initiatives and the aquaculture industry, both of which play a vital role in the health of rural economies and ecosystems, and their combined efforts will be crucial in developing sustainable solutions for the future of Scotland’s wild salmon.

Jon Gibb of the Salmon Scotland Wild Fisheries Fund, whose financial assistance made this project possible, said: “Atlantic salmon are in deep trouble, due mainly to climate and habitat change, and we need to do everything we can to work together in understanding how we can mitigate against this collapse. The study's findings are an important milestone in that journey and point towards the most judicious use of stocking for the most threatened populations. I am delighted that the Wild Fisheries Fund could underpin this vital study into the impacts of long-term stocking into the River Carron.”

The River Carron Conservation Association has worked tirelessly to enhance biodiversity in the river’s surrounding ecosystem, including planting 370,000 trees on the Glencarron Estate alone. This report stands as a pioneering example demonstrating of how conservation stocking, when implemented effectively, can play a crucial role in supporting and restoring native Scottish salmon populations, allowing time for integration and maturity of ecological methods necessary to ensure sustainable recovery.

Crucially, the study offers key lessons on mitigating some of the negative effects traditionally associated with stocking, while also presenting a potential means to reduce the genetic impact of Norwegian aquaculture strains on wild salmon populations, delivering insights that will guide best practice in future conservation programmes.

Issued by Tartan Silk Public Relations