26-27 March 2019
University of Stirling
Successful production of sterile fish (via triploidisation or other means) on a commercial scale would be advantageous for the following reasons...
1) increased growth due to reduced energy use for gonadal development
2) reduced risk of wild stock hybridisation by reproduction with escaped farmed fish (should they have access to them)
Since the 90s (when triploid finfish were shown to perform poorly) there have been substantial advancements in our understanding of triploid finfish husbandry and the development of new gene editing techniques to induce sterility - both of which may allow optimal production of sterile finfish.
This workshop highlighted the work of the Salmotrip+ project (funded by BBSRC and Innovate UK in collaboration with Mowi, BioMar and Pharmaq) which aimed to optimise triploid salmon farming. A wide range of perspectives from academics and industry stakeholders from Norway, America, Canada and Tasmania were also provided. The latter of which where triploidisation has been used for decades as a tool to combat early maturation, as the usual use of lights is ineffective in turbid Tasmanian waters.
Led by Prof Herve Migaud of the University of Stirling, Salmotrip+ demonstrated that lower egg incubation temperatures and the inclusion of increased phosphorous (or probiotic use to improve nutrient uptake) in young triploid salmon diets improved triploid performance and health, forming the basis of a 'best practice' guide for triploid production. Tom Fraser, Institute of Marine Research (IMR), provided further examples from Norway where reduced egg incubation temperatures mitigated the appearance of bone malformations which has historically deterred producers from investing in triploid culture.
Further talks commented on other aspects of triploid fish husbandry, including that from Dr Mikey Clarkson (University of Stirling), who recommended that eggs stripped within 5 days of ovulation should be used for triploid culture, reducing egg mortality and parr size variation. Dr Lynn Chalmers emphasised that side effects associated with intraperitoneal inoculation with oil adjuvanted vaccines were no more prominent in triploid than diploid salmon, meaning that triploids are able to withstand routine on-farm vaccine operations. However, the temperature sensitivity of triploids was re-iterated by Dr Chalmers who found that above 12 degrees, triploid salmon experienced higher mortalities in response to H2O2 seawater treatment.
Triploid salmon temperature sensitivity was partly explained by Prof Tillmann Benfey (University of New Brunswick) who revealed that triploids may have a reduced aerobic scope, meaning that they have less aerobic capacity available to cope with stressful situations whilst maintaining basic body function.
New sterilisation techniques, such as gene-silencing, were described by Helge Tveiten (NOFIMA), which prevent the formation of functional gonadal tissue in otherwise 'normal' fish; research is currently ongoing to develop a vaccine to induce this gene-silencing effect in diploid offspring. Anna Wargelius, (IMR), demonstrated another alternative sterilisation technique which involves knocking-out primordial germ cells (PGCs), the developmental precursor to gonadal tissue development.
The requirement for simple and reliable finfish sterilisation methods is evident but industry implementation of new technologies comes with inherent challenges. In the case of triploid finfish, adaptation of routine husbandry processes will be required for optimal performance, as Herve Migaud stated, "triploids should be treated as a new species". There is currently no custom made triploid breeding tools, however, AquaGen announced that new triploid software is in development to aid the identification of diploid and triploid parents. Certification of new sterilisation techniques will also take time, a message emphasised by Debbie Plouffe of the Centre for Aquatic Technologies, Prince Edward Island who explained the FDA regulation of AquaBounty's 'AquAdvantage' salmon which must be sterile and sufficiently contained for rearing in commercial conditions in Canada.
Education and understanding of sterile fish at all levels will be key to the development and uptake of new technologies. Visibility and transparency with consumers, regulators and politicians will also be vital. Workshop attendees collectively agreed that academics can contribute to changing opinions by considering the language used to describe triploid finfish deformities, taking care to differentiate between visible deformities and minor less commercially-relevant malformations detectable only by x-ray. With further international collaboration, the integration of applied and fundamental research, and the certification of new sterilisation tools and techniques, successful sterile finfish cultivation in the UK is possible.
Information for the above summary was taken from a report written by Christopher Mitchell of PHARMAQ for use by Fish Farmer Magazine.
Further reports generated by Rob Fletcher on The Fish Site are below...
How to commercialise sterile finfish production
Does gene editing effect salmon health and welfare?