Climate change and selective breeding in aquaculture

Abstract Text: Aquaculture is an important sector that strengthens food security. Based on FAO, aquaculture production has to increase up to 42.9% to meet the global population demand in 2020. According to the reports by IPCC and FAO, climate change may result in global warming, sea level rise, changes of ocean productivity, water shortage, and more frequent extreme climate events. Climate change may affect aquaculture directly and indirectly, depending on climatic zones, aquaculture activities, and farmed species. Climate change may introduce opportunities; - rise of temperature may increase growth and open up new farming opportunity due to aquatic species migration, as well as, several challenges to aquaculture. First, genotype-by-environment interactions (GxE) may increase because aquatic animals may expose to more fluctuating rearing environments. Rainbow trout (Oncorhynchus mykiss) – the most popular farmed salmonid worldwide, has a very narrow range of optimal temperature to grow. The magnitudes of GxE, i.e., average genetic correlation (r_g), from 1964-2013 were reviewed across 38 species. The review revealed strong re-ranking for growth of rainbow trout in different temperatures (r_g= 0.36), indicating lower-than-expected production in suboptimal rearing temperature when selecting for growth based only on optimal rearing temperature. Second, it can be hypothesized that climate change may increase environmental variance in sensitive genotypes. Third, climate change may facilitate an outbreak of (new) pathogens or parasites, increasing mortality and hence reducing production. Fourth, 20 % reduction of ocean productivity worldwide has been predicted, implying a decline of fishmeal and fish oil supplies and hence the replacement of the raw materials may become more important in the future. Finally, reduction in biodiversity may threaten genetic variation and the ecosystems of wild stocks. Furthermore, this may imply a lack of founder populations for breeding in the future. To ensure the food security, the impacts of climate change have to be addressed through resource management, reduction of environmental impacts, and selective breeding strategies. Breeding goals may change towards “resilience”, i.e., stability of performance under fluctuating rearing environments or towards new trait mean. The breeding goals may include disease resistance or tolerance for emerging pathogens and parasites. Anyhow, more research is needed to better understand the opportunities of selective breeding for resilient animals in aquaculture under climate change. To avoid any loss of biodiversity in wild stocks, an international gene bank of the wild stocks may store genetic resources of founder populations for future breeding programs.

Keywords: climate change, genotype-by-environment interaction, selective breeding