Modeling the Effects of Age-Specific Spawning Behaviors and Environmental Variability on Pacific Ocean Perch Population Dynamics in the Gulf of Alaska

In commercially exploited, long-lived fish species, age structure plays an important role in determining population stability and resilience to human and environmental impacts. An increase in energy allocation per offspring by older females has been observed for some rockfish species, which can improve larval survival through an increased time to starvation and higher likelihood of encountering favorable environmental conditions once released. Females of different age and size may also spawn earlier or over a more protracted season. Thus, populations with a broad age structure can potentially contribute to population stability through increased larvae quality and an increased range of spawn timing and locations. Data collected on Pacific ocean perch (POP) in the Gulf of Alaska suggest that older POP females spawn earlier than younger females, that older females provision their larvae with larger oil globules, and older females have less variable oil globule size. In addition, independent of female age, oil globule volume declines through the spawning season for both young and old females. We parameterized an individual-based model with these age-specific spawning behaviors to explore the effects of age structure and spatio-temporal variability in environmental conditions on POP population dynamics in the Gulf of Alaska.