Fish domestication in aquaculture: reassessment and emerging questions
Historically, aquatic products were derived from wild capture fishes. However, declining marine catches since the early 1990s, combined with an increasing demand for fish products, has created a strong impetus for aquaculture. By 2014, half of global seafood consumption originated from aquaculture. The rise of aquaculture production has relied mostly on the domestication of a growing number of teleost fishes. In total, 250 species belonging to 71 families have been farmed since 1950. Among the 250 species, 183 were still produced in 2009. This implies that 67 species had been farmed only for a short time (most often less than five years). Nearly 70% (n = 175) of the species farmed in 2009 were classified in the first three levels of domestication; the other 75 species reached levels 4 and 5, and might be considered as domesticated. The 35 species classified at level 5 belong to ten families, including Cyprinidae (n = 10), Salmonidae (n = 8), and Acipenseridae (n = 5). More than 90% of global production was based on only 20 species in 2009. This shows that aquaculture production is heavily skewed toward the farming of a few (often alien) species. Conversely, these data suggest that most domestication experiments have failed to reach significant volumes. However, a growing interest in promoting native species in aquaculture, particularly in South America, has resulted in significant changes. The strong development of alien and native aquaculture around the world, along with various supplementary hatchery stocking programmes, has resulted in billions of captive fish belonging to over 300 species being either accidentally or deliberately released into the wild each year. Yet, captive fish differ from their wild counterparts, and may develop phenotypes that are maladaptive in nature. Therefore, the release of hatchery-reared fish should be considered after other measures (e.g. limiting harvests, and habitat restoration or modification) have failed, and all efforts should be made to prevent farmed fish from escaping into the wild.