UC Davis

Accounting for species interactions is a key component of ecosystem-based management. Simple models of species interactions provide a framework for making qualitative comparisons and identifying critical dynamics. A review of multispecies-fisheries and marine-reserve models indicates that incorporating species interactions leads to decreased theoretical predictions for sustainable yield and harvest rates and to increased theoretical predictions for the reserve size necessary to protect populations; ontogenetic shifts in interactions also have a significant effect on multispecies model predictions. While previous models have explored negative species interactions (i.e., predation and competition), this paper presents an example marine reserve model with a positive interaction: a spiny lobster-sea urchin-red algae trophic chain where red algae facilitate lobster recruitment. Model results indicate that recruitment facilitation primarily affects the time scale of the species dynamics and the lobster spillover from reserves to harvested areas; the direction of these changes depends on the no-facilitation baseline. Overall, these models indicate the importance of incorporating species interactions into fisheries and reserve management decisions.