Effects of stage specific habitat use; implications of complex life cycles on population management

Species exhibiting ontogenetic diet shifts often change habitat between adult and juvenile life stages. Within stage processes such as competition or mortality may affect other life stages in different habitats. In this paper we study the effect of different processes on specific stages on a consumer population. A consumer-resource model is used, and stage specific habitat productivity, mortality and survival are varied. Our results indicate that for intermediate differences in habitat productivity juvenile or adult biomass dominated states can occur alternatively. When adult and juvenile habitat are more different a single equilibrium exist. Increased mortality decreases the scope for alternative stable states. Juvenile mortality in particular is more detrimental for population persistence than background or adult mortality, especially in combination with relative low productivity in the adult habitat. These findings are of interest when managing fish stock and implementing marine protected areas.