Does poor maternal condition reduce early offspring performance in the wild?

The extent to which mothers invest in their offspring varies greatly among and within species, and can have pronounced effects on the viability and survival of those offspring. Any maternal contribution is limited by the resources available to the mother, and so will vary with her nutritional state (and hence environmental conditions). Furthermore, if mothers face poor or unpredictable conditions (and so cannot predict the environment of their offspring), they may alter the characteristics of their offspring, either as a physiological constraint or as a bet-hedging strategy, by investing unequally across the family, increasing the possibility that at least some individuals will survive. However, the links between environmental quality, female condition, offspring variability and offspring performance are not well understood. This project will be the first to examine the highly pertinent question of whether a documented decline in average maternal condition in a wild fish population, caused by environmental change, is affecting the ability of offspring to cope with harsher environments. The project will be based on Atlantic salmon. The mean fat content of female salmon returning to Scottish rivers to spawn has shown a continuous and significant decrease in recent years (11-14% per decade), linked to increases in winter sea surface temperature. The effects of this reduction in condition on the eggs and the resulting offspring are unknown. In this project we will relate female condition to a diverse range of egg characteristics likely to influence viability, and in a unique and novel experiment will investigate the consequences of variation in maternal condition on offspring performance under differing levels of competition in the wild. Salmon returning to the River Conon to spawn will be classified according to their body condition, and eggs from females in good and poor condition will then be planted out into natural streams that lack salmon due to impassable upstream barriers. The survival rate of the fry will be related to the body condition of their mother, using DNA fingerprinting to establish the parents of each recaptured fish. In parallel with this field work we will measure various traits of the eggs and fry in the lab, to determine how the body condition of the mother influences the characteristics of the offspring.