Maternal fitness consequences of interactions among agents of mortality in early life of salmonids

Maternal effects can be key determinants of female fitness through their influence on survival in early life. In salmonid fishes, three density-dependent sources of offspring mortality are redd superimposition, predation, and starvation. An individual-based model was developed to explore how these sources of mortality can affect functional relationships among maternal fitness, maternal phenotype (body size), spawner density, and spawning timing. We found that the strength of the relationship between maternal size and fitness was highly context-dependent, differing with the source of offspring mortality and with interactions among the mortality agents. Component Allee effects at low spawner densities were also detected in some simulations. The results reveal unanticipated interactions among offspring mortality sources, maternal body size, and fitness. Given the high probability that these mortality sources differ considerably across variable temporal and spatial scales, there would be considerable value in obtaining field-based empirical data to test the predictions proffered here to better understand the correlates of maternal fitness in salmonid fishes.