Ecological relevance of laboratory studies with brown trout embryos: hatchling size, carotenoids, and sex predict juvenile performance in the wild

Abstract

AbstractLaboratory studies on embryos of salmonids, such as the brown trout (Salmo trutta), have been used extensively to study factors influencing offspring performance. These studies are based on the implicit assumption that early life-history traits are relevant for growth and survival in the wild. Here we tested this assumption. We used gametes of wild-caught brown trout to perform a block-wise full-factorial breeding experiment, with some of the resulting offspring we carried out controlled laboratory experiments, and released the remaining offspring into a natural streamlet. We recaptured 0+ juveniles after their first summer in the wild and used microsatellite and sex-linked markers to determine sex-specific growth and survival for each of the 60 experimental families. We also recorded mean egg size and carotenoid content per female to evaluate their importance for juvenile growth and survival. We found strong correlations between laboratory performance and growth, but not survival, of 0+ juveniles in the wild. Egg size positively influenced juvenile growth. We also found that male juveniles grew faster than females. Juvenile survival seemed not influenced by egg size, but we observed a significant male-biased survival for eggs with a high zeaxanthin content (a carotenoid). This first observation suggests that female reproductive strategies can have sex-specific effects that need to be better understood. We conclude that embryo performance in controlled environments (laboratory or hatchery) can be useful predictors of offspring growth in a natural setting.Highlights60 full-sib families were raised under experimental conditions and in the wildHatchling size in the laboratory predicted juvenile growth in the wildEvidence for sex-specific effects of egg carotenoids on juvenile survival