I sometimes feel like a broken record: “disease remains one of the most significant challenges facing aquaculture” appears in almost every newsletter. But it bears repeating. From Tenacibaculum in Atlantic salmon to MSX and Dermo in oysters, disease outbreaks can cause substantial mortality, production losses and ecological challenges.
In this issue, we are exploring an approach we have not covered before: selective breeding. We have discussed additives, vaccines and early detection, but breeding offers another way to build disease resilience over time. For diseases such as MSX, it is one of the few available options. By identifying and breeding aquatic animals with desirable traits, researchers and producers can develop stocks that are more resilient to disease, better suited to farming conditions and more productive.
Selective breeding may be new to our newsletter, but it is not new to aquaculture. Established programs have improved growth rate, feed efficiency and disease resistance in species such as Atlantic salmon and shrimp. Advances in genomic selection are expanding these opportunities. Combining genetic information with performance data helps researchers identify animals with desirable traits and make more informed breeding decisions.
The potential benefits extend beyond survival. Healthier, more resilient stocks may experience fewer losses, use feed more efficiently and support a more reliable supply of farmed seafood. For producers, this can mean less production uncertainty and greater economic resilience. For the wider industry, it offers a way to strengthen production while using resources responsibly.
Breeding programs also raise environmental questions beyond the risk of farmed animals escaping. A narrow breeding pool can increase inbreeding and reduce the genetic diversity needed to respond to future challenges. Wild genetic resources need protection, too. Where farmed animals can reproduce with wild relatives, interbreeding may alter wild populations. Introduced stocks may also compete with native species. These risks vary by species and production system, so responsible breeding requires careful genetic management and safeguards suited to the surrounding ecosystem.
There is also an ethical question: what counts as an improvement? Faster growth and higher survival should not be the only measures of success. For farmed fish, breeding goals should also consider welfare, including health, normal development and the ability to cope with farming conditions. Disease resistance should complement good husbandry, not justify conditions that compromise animal wellbeing. Responsible breeding means evaluating trade-offs openly and pursuing gains in animal health without placing unacceptable risks on wild populations or ecosystems.
The need for disease resilience is particularly clear in Prince Edward Island’s oyster industry. Breeding oysters with improved disease resistance offers a potential long-term response. But identifying oysters that survive an initial exposure is only the starting point. Researchers also need to understand how disease develops, how oysters respond and which biological traits may be associated with greater resilience.
Collaborative research underway in PEI with Canada’s Ocean Supercluster is addressing these questions. Led by Atlantic Aqua Farms, in partnership with Onda and CAT, the project is advancing MSX-resistant oyster seed through genomic selection. It is also developing an MSX disease model and investigating biological markers associated with oyster immune responses.
Selective breeding can improve disease resistance over generations, but it is not a standalone solution. Programs must maintain genetic diversity, evaluate resistance against relevant disease threats and support breeding outcomes with research, diagnostics and ongoing surveillance.
The work in PEI illustrates both the opportunity and the complexity. More resilient oyster stocks could help protect an important regional industry and ecosystem. Achieving that goal requires a deeper understanding of MSX, Dermo and the biological responses that shape disease outcomes.
Ultimately, the goal is more than breeding animals that perform well under one set of conditions. It is to build the scientific evidence and practical tools needed for healthier stocks, more resilient production systems and a sustainable aquaculture industry.