A new collaborative study, carried out between 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 salmon in the United Kingdom.

Photo by Gingerbreadmedia / Pixabay

Wild salmon populations have suffered extreme declines in Scotland, and in some rivers conservation stocking may be the only option available to prevent the complete loss of the threatened populations. It was therefore essential to carry out well monitored studies to maximise the long-term success of conservation programmes and establish best practices to eliminate the potential genetic risks and ecological impacts traditionally associated with stocking.

Key insights included:

• It is possible to mitigate the risks to long-term genetic health associated with captive broodstock programmes by breeding from wild-caught fish in the hatchery for a single season, rather than retaining females in captivity for multiple breeding cycles.
• Fish released at the autumn (late) fry stage exhibit significantly higher survival rates compared to those released at different life stages.
• While genetic material from Norwegian strains, introduced by commercial aquaculture escapees, was detected in both wild-spawning and captive broodstocks, 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.
• Incorporating fast-turnaround genetic testing into conservation stocking programmes could enable selectively avoiding breeding from genetically compromised fish.