Non-native species weaken diversity-mediated stability in aquaculture

Species diversification can stabilize food production, but it remains unclear whether diversity gained through non-native species stabilizes production as effectively as diversity based on native taxa. Here we show, using seven decades of FAO aquaculture production records (1951-2020) linked to native-range assignments and environmental and socioeconomic covariates, that non-native species significantly increased national aquaculture diversity and observed overall production stability but significantly weakened diversity-mediated stability. Compared with native-only portfolios, total-species portfolios had lower estimated stabilizing effects of aquaculture diversity in 74.1% of nations, by 43.3% on average among nations showing lower effects. This weakening was associated mainly with reduced mean species stability rather than reduced interspecific asynchrony, and was strongest where non-native species contributed more production, aquaculture area was smaller and GDP per capita was higher. Our findings show that introductions can broaden aquaculture portfolios while weakening the mechanisms by which diversity stabilizes aquaculture production through time. Food-security strategies should therefore evaluate introduced species for temporal stability as well as productivity, while expanding locally adapted native species and building portfolios with high species-level production stability.