Aquaculture potential evolution during early domestication trials in a model species (Danio rerio) with different breeding strategies

Domestication is a cornerstone for diversifying aquaculture, and the feasibility of domesticating a wild fish population can be assessed through its aquaculture potential (i.e., a measure based on key phenotypic traits related to growth and reproduction in captivity while meeting stakeholders' expectations). As domestication modifies these traits, aquaculture potential is expected to evolve over generations, influenced by breeding strategies. However, little is known about how different management approaches may shape this evolution during early domestication. In this study, we tracked changes in aquaculture potential over four captive generations of wild-caught zebrafish (Danio rerio), subjected to three breeding strategies: no selection (NS), single-function selective breeding program (S-SBP; growth-related traits), and multi-function selective breeding program (M-SBP: growth, reproduction, welfare). S-SBP and M-SBP employed within-family selection based on a phenotypic index. We developed a standardized Aquaculture Potential Score (APS) integrating growth (standard length, height/length ratio, specific growth rate), reproductive (fecundity, sperm motility), and welfare traits (stress-induced cortisol, Fulton's condition factor). Trait evolution was assessed using linear model predictions and genetic trends based on estimated breeding values and heritability derived from pedigrees. Selective breeding (S-SBP and M-SBP) rapidly improved growth and morphometric traits, whereas NS lines showed minimal change. Reproductive and welfare traits, however, remained largely static due to both low heritability (h² < 0.20) and environmental modulation. Consequently, APS remained stable across generations, with growth gains offset by stagnation in other domains. These findings underscore that (i) early selection may effectively improve high-heritability traits; (ii) composite metrics like APS may obscure divergent trait responses.