Conservation of Atlantic salmon - gene banking: principles and considerations

Summary conclusions

Gene banking of salmonids enables the long-term preservation of valuable genetic diversity in the face of external stressors. In extremis, it offers one of the few tools to avoid population expiration, which may be especially important where external stressors cannot be addressed. Further, a comprehensive sampling can provide a type of bio-insurance against nationwide genetic biodiversity loss in the face of continued stressors that cannot be ameliorated. Gene banking is not without risks, however, well thought-out plans and the development and standardization of efficient protocols may be able to address such risks to a large extent.

The two types of gene banking, live and cryobanking both offer opportunities and costs and may be applicable in different situations. For example, live gene banking is a relatively expensive option, and it is difficult to envisage a programme that maintains the genetic characters of the numerous salmon populations across the whole country. However, as has been seen in programmes, such as the Norwegian Gene Bank, live gene banking can be very effective in short term maintenance of specific populations while specific external stressors (such as the parasite G. salaris) have been addressed as it can maintain both male and female genetic characteristics, and can be used in conjunction with cryobanking.

Cryobanking of sperm would seem to be a much more cost-effective approach for the capture of genetic diversity, allowing comprehensive strategic coverage of multiple populations as insurance against future stressors. It should be noted that duplicate sites may be required for disaster contingency but also that space and apparatus requirements are modest. Contrary to live gene banks, the genetic material is not exposed to selection while stored and can be transferred across time and space. The method, thus, has the potential to provide bio-insurance against genetic diversity loss, restore lost populations, and/or to enhance those threatened by extirpation and or genetic degradation. The programme could be run as a collaborative enterprise, with a central cryobank repository (or duplicated repositories) and material collected by numerous stakeholder organisations supplied for preservation (following strict collection protocols). Importantly, cryobanking takes a snapshot of a genetic profile of a salmon population, which may be augmented in subsequent years. If changes in the environment that led to a weak population cannot be addressed, then in some cases the original genetic material may not be most appropriate on its own in seeking to restore a viable stock of salmon.