The onset of sexual maturation in salmonids is conditional on performance surpassing a threshold. Although the basis on which this performance threshold is founded is still not clear, the primary signal(s) appears to be associated with size and condition. The magnitude of the performance threshold, which can vary across populations, influences the incidence of sexual maturation within a population. Applying selection pressure to the performance threshold could be an effective approach to improve control of sexual maturation in cultured populations. However, the prospect of intra-population variation in the performance threshold for sexual maturation onset remains largely unexplored.
We investigated the relationship between size, condition and sexual maturation outcome in Atlantic salmon (Salmo salar) from the SALTAS selective breeding program. Males that were sexually mature at 2 years of age (maiden spawn) had, on average, greater size and condition than their immature counterparts in the previous winter. For every 10 mm increase in winter fork length or 0.1 K increase in winter condition, the odds of being sexually mature at 2 years of age increased by 1.48 times or 1.24 times, respectively. Family explained 35.66 % of the variation in sexual maturation outcome amongst 2 year-old males that was not attributable to the average effects of fork length and condition. Our findings suggest that the performance level required for sexual maturation onset varies between families from the SALTAS population. This could support the application of selection to advance or delay sexual maturation onset in the studied population.