Chapter 2: Sustaining Atlantic Salmon in the Northwest Atlantic: Considerations from a Life History Perspective
Jeffrey A. Hutchings
Life histories reflect the ways in which individuals vary their age-specific expenditures of reproductive effort in response to physiological, developmental, genetic, and environmental influences on age-specific rates of survival and fecundity. Having direct influence on fitness, life history traits include characteristics such as age and size at maturity, number and size of offspring, and number of reproductive events per lifetime (Roff 1992). One implicit assumption of life history theory is that natural selection favours those genotypes whose age-specific schedules of survival and fecundity generate the highest per capita rate of increase relative to other genotypes in the same population (Roff 1992; Charlesworth 1994). That is, selection is assumed to maximize an individual’s intrinsic rate of natural increase, r, as given by the Euler-Lotka equation.