Growth of brown trout in the wild predicted by embryo stress reaction in the laboratory.

Laboratory studies on embryos of salmonids, such as the brown trout (Salmo trutta), have been extensively used to study environmental stress and how responses vary within and between natural populations. These studies are based on the implicit assumption that early life-history traits are relevant for stress tolerance in the wild. Here we test this assumption by combining two data sets from studies on the same 60 families.

Parental kinship coefficient but not paternal coloration predicts early offspring growth in lake char.

The 'good genes' hypotheses of sexual selection predict that females prefer males with strong ornaments because they are in good health and vigor and can afford the costs of the ornaments. A key assumption of this concept is that male health and vigor are useful predictors of genetic quality and hence offspring performance. We tested this prediction in wild-caught lake char (Salvelinus umbla) whose breeding coloration is known to reveal aspects of male health.

Sex-specific effects of inbreeding in juvenile brown trout.

Inbreeding depression, that is, the reduction of health and vigour in individuals with high inbreeding coefficients, is expected to increase with environmental, social, or physiological stress. It has therefore been predicted that sexual selection and the associated stress usually lead to higher inbreeding depression in males than in females. However, sex-specific differences in life history may reverse that pattern during certain developmental stages.

Sperm of more colourful males are better adapted to ovarian fluids in lake char (Salmonidae).

Fish often spawn eggs with ovarian fluids that have been hypothesized to support the sperm of some males over others (cryptic female choice). Alternatively, sperm reactions to ovarian fluids could reveal male strategies. We used wild-caught lake char (Salvelinus umbla) to experimentally test whether sperm react differently to the presence of ovarian fluid, and whether any differential sperm reaction could be predicted by male breeding coloration, male inbreeding coefficients (based of 4150 SNPs) or the kinship coefficients between males and females.