Back to search

HAVBRUK2-Stort program for havbruksforskning

TripGenWelfare: The influence of inbreeding and aberrant inheritance on welfare in gynogenetic, triploid, and tetraploid Atlantic salmon

Alternative title: TripGenWelfare: Påvirkningen av innavl og avvikende arv på velferd i gynogenetic, triploid, og tetraploid atlantisk laks

Awarded: NOK 7.6 mill.

Farmed Atlantic salmon are an economically important industry in Norway and the world. However, the farming industry has some sustainability challenges, like the negative impact of escapees interbreeding with wild salmon. Farming sterile triploid salmon can stop interbreeding between escapees and wild salmon. Triploids have two copies of DNA from their mother and one copy from their father, unlike conventional diploids (one copy of DNA from each parent). Triploids occur naturally, but rarely, in the wild. In the industry, they are produced by giving newly fertlised eggs a brief pressure treatment, which is non-invasive, easily implemented and has a high success rate. However, triploids often have welfare issues. For example, they get sick more frequently than diploids and are more sensitive to higher water temperatures. So, the farming industry relies on diploids, despite the benefit of sterile triploids. We previously found some interesting changes in triploid DNA, which we did not find in diploids from the same families. We suggest that these changes come from the pressure treatment, which may cause the welfare challenges in triploids. We also think that the extra DNA from the mother is causing a so-called “inbreeding” effect in triploids. Since project start-up, we have produced diploid, triploid and gynogenetic salmon (only containing the mother’s DNA) and will follow them through their lives to see if there are differences in welfare or growth between them, and examine their DNA for any differences. We have produced salmon which should be triploid using sub-optimal pressure treatments and diploid and triploid controls to see how the treatment affects their DNA and are also following these fish through their lives to see how their growth and welfare is affected. Finally, we have tried to produce tetraploid salmon (two copies of DNA from each parent) that could be used to naturally breed with diploids and produce triploids without a pressure treatment. Triploids may then be more appealing to salmon farmers, stopping interbreeding between escaped farmed and wild salmon, making the farming industry more sustainable and helping to protect wild salmon populations.

Escapees are a major challenge to sustainable Atlantic salmon aquaculture, and sterile triploid salmon are a solution. Triploid salmon are produced by a pressure shock and contain two copies of maternal and one copy of paternal DNA. The use of triploids commercially is limited by poor welfare and performance. We hypothesize that doubling of the dam genome may cause an inbreeding effect in the offspring, that, dependent on the heterozygosity of the dam, could explain the lower performance and welfare observed. We will examine the potential inbreeding effect using controlled experiments comparing diploid, pressure-induced triploid and gynogenetic (inbred) diploid full siblings. Gynogenes are diploid offspring containing two copies of only the maternal DNA. We will follow the different groups, assessing fish for performance and welfare. We will use a mixture of genomic and genetic methods to assess the level of inbreeding across the entire genome in each group and compare this to individual performance, which has never been done in triploid Atlantic salmon. We also hypothesize that a sub-optimal protocol may lead to unintended effects on triploids as hydrostatic pressure treatment is known to cause chromosome aberrations. To examine the nature and prevalence of chromosome aberrations resulting from pressure-shock treatment we will assess the incidence and types of errors and how they influence triploid performance/welfare by linking individual performance in controlled experiments to observed chromosome aberrations using genetic tools. An alternative method to produce triploid salmon is by producing tetraploid individuals and breeding them with standard diploids to produce triploids with higher levels of heterozygosity compared to traditionally produced triploids. This has never been done in Atlantic salmon; therefore our final aim is to produce the world´s first Atlantic salmon tetraploid line with the goal of producing triploids by crossing them with diploids.

Funding scheme:

HAVBRUK2-Stort program for havbruksforskning