Understanding Triploid Salmon

Triploid salmon are a unique breed of farmed fish made sterile through high-pressure treatments applied to fertilized eggs. According to researcher Aurélien Delaval, “The eggs are exposed to high pressure shortly after fertilization, resulting in the fish retaining three sets of chromosomes instead of the usual two. This makes the salmon triploid and sterile.”

The Benefits of Sterility

The primary advantage of sterile salmon is their inability to breed with wild salmon, which significantly reduces the risk of genetic mixing and helps preserve wild populations. However, these benefits are accompanied by challenges.

Health Challenges in Triploid Salmon

Research indicates that triploid salmon generally exhibit poorer health compared to their diploid counterparts. Delaval notes, “Triploids are more prone to skeletal and heart deformities, cataracts, infectious diseases, and skin ulcers.” This raises concerns regarding the overall welfare of these fish in aquaculture settings.

Initially, the researchers hypothesized that inadequate pressure during the treatment could lead to these health issues. To test this theory, they conducted experiments using salmon eggs from various family lines.

Investigating Pressure Treatment Effects

The study involved exposing salmon eggs to five different pressure treatments:

• No pressure (0 PSI), resulting in regular diploid fish.
• Full pressure (9500 PSI), the standard for inducing triploidy.
• Three intermediate treatments (6500 to 8500 PSI), which allowed for comparison across family groups and the health of the resulting fish.

“Our results indicated that suboptimal pressure caused genetic issues, leading to low hatch rates,” says Delaval. Among the few survivors from these treatments, some were true triploids while others remained diploid.

The Role of Family Lineage

The key finding was that a fish’s family background had a more significant impact on health and growth than the pressure treatment itself. Delaval explains, “Some triploid families performed better than others, with certain families showing growth and health levels comparable to diploid siblings.”

This variation suggests the potential for selective breeding to enhance the welfare of triploid salmon. “Our next step is to delve deeper into this area to understand how selective breeding can improve performance and welfare in triploid salmon,” Delaval mentions.

About the Research Project

The research is part of the TripGenWelfare project, funded by the Research Council of Norway. Its primary focus is to investigate the genetic factors affecting welfare and performance in triploid salmon.

Reference

Delaval, A., Glover, K. A., Solberg, M. F., Fjelldal, P. G., Hansen, T. J., Pedersen, A. Ø., Sambraus, F., Garnes-Gutvik, S. N., & Harvey, A. C. (2025). Inducing failed triploidy: The effects of sub-optimal hydrostatic pressure treatments on Atlantic salmon growth and welfare. Aquaculture, 608, 742743.

Photo Credit: Erling Svensen/Havforskningsinstituttet