Survival of prey growing through gape-limited and apex predators

Abstract

A mechanistic model based on first principles of growth and predator-prey behavior introduces the effects of a predator size distribution on the survival of rapidly growing prey. The model, fit to Chinook salmon data, can explain the observed increase in ocean survival with smolt ocean entrance length using different predator size-frequency distributions. The model introduces new dimensions to theories on predator-prey interactions and population recruitment and suggests the possibility that fish recruitment control can be highly variable; sometimes dominated by juvenile growth and encounters with gape-limited predators and other times dominated by adult encounters with apex predators. Additionally, a sensitivity analysis suggests that scale and otolith circuli spacing are insensitive indicators of size-selective mortality but the profile of adult survival with juvenile length provides information on the balance of size-dependent and size-independent mortality processes.