Probabilistic maturation reaction norms for age and size at maturation of chum salmon in Korea
Studies of fisheries-induced maturation evolution have revealed shifts towards smaller sizes and younger ages at maturation. In this context, probabilistic maturation reaction norms (PMRNs) serve as a new statistical tool that helps to disentangle phenotypic plasticity and evolutionary responses by describing the probability of individuals to mature as a function of their age and size. This perspective overcomes the otherwise confounding effects of changes in growth and survival on observed patterns of maturation. Chum salmon are semelparous fish in the North Pacific that spawn in freshwater and reproduce only once during their lifetime. I plan to calculate PMRNs for age and size at maturation of the chum salmon population spawning in the Namdae River in Korea, which constitutes the southern boundary of the natural range of chum salmon in the North Pacific. The estimation of PMRNs could make it possible to comprehend the effects of varied environmental conditions and size-selective fishing pressures on the life history of chum salmon. Therefore, my study will concentrate not only on environmental variability in life-history traits, but also on the effects of fisheries-induced evolution compared with environmentally induced changes on age and size at maturation.