Conservation of Atlantic salmon - gene banking: principles and considerations

Risks of gene banking

Notwithstanding the opportunities of gene banking, there are also risks associated with such programmes. Such risks include:

• Cost
  • It is especially the case with live gene banks and the running of hatcheries, but cryobanking too has resource implications associated with it if it is to be carried out properly. Both scenarios require bespoke facilities and expert staff, and setting up such a programme will require significant training. Costs are also ongoing throughout the lifespan of the programme and this may be decades if stressors are not addressed. There is an inevitable risk that funding will not be sustained for the duration of a long restoration programme.
• Specialist skill sets
  • The various aspects of a gene banking programme as outlined above require a number of specialist skill sets. Such skills may not be available, so a specialist team would have to be trained and skills developed. Inevitably, there will then be ongoing risks associated with maintaining an appropriate team.
• Resources diversion
  • Resources could be diverted from other management and/or conservation strategies. While, in extremis, gene banking may be the best and only option, in many cases there may be other, more appropriate, options that can be explored to boost population health.
• Loss of species genetic diversity
  • A species relies on the genetic diversity across populations to ensure it is resilient in the face of environmental stressors and has the ability to adapt to changing conditions (the portfolio effect). It might be extremely difficult to ensure all diversity is captured across a range when considering the many sub-structured populations present. It may be far better to spend resources removing the stressor acting on all the populations if possible.
• Loss of population genetic diversity
  • The aim of a gene banking programme is to conserve genetic diversity. This may be extremely difficult to do considering the complex life history type of salmon populations. There is thus a significant risk that gene banking may result in a loss of local adaptation, even if best practices in sampling and crossing are followed.
• Loss of local adaptation
  • It may be extremely difficult and/or costly to ensure only fish from a specific population are incorporated into a gene banking programme. Thus, there are significant risks that populations will be hybridised with consequent potential loss of local adaptation and fitness in the wild.
• Genetic damages to cryopreserved milt
  • An absolute requirement for the use of cryopreserved sperm is that the freezing, cryobanking, and thawing processes does not alter the information carried by the cellular genome. Such changes may lead to development abnormalities and losses of genetic information in the progeny. It is thus vital that protocols are followed that negate these effects.
• Genetic or epigenetic effects in offspring derived from cryopreservation
  • It has been shown that cryopreservation may promote selection of spermatozoa resistant to the freezing procedure, and that more tolerant sperm cells to freezing is a trait carried over to offspring. Thus, a cryopreservation procedure undoubtedly has the potential to have an environmentally induced effect on sperm properties, which may lead to genetic effects carried over to offspring.
• Adequate planning and monitoring
  • It is vital that planning and monitoring of a programme are adequate to ensure best practice and the correct protocols are followed. This is not a trivial task when running such a programme and may not always be achievable, especially at a local level.
• Storage vessel failure
  • Storage vessels may fail such that the temperature rises to unacceptable levels. Consideration of the use of self-replenishing nitrogen vessels with alarms may offset this risk to an extent, although with an associated rise in costs.
• Single site failures
  • Obviously, a gene bank will contain a large amount of valuable genetic material and so can act as a single point of failure with significant negative impacts if there are problems at a facility. Consideration of the need for replication is thus required, with the associated resource costs that this brings.

As there are numerous differing situations where gene banking might be an option, these risks would have to be assessed on a case-by-case basis for each scenario, including expert inputs on planning options, in order to avoid doing more harm than good.