Abstract
With the recent declines in production and overharvesting of fisheries worldwide, the importance of understanding the age and spatial structure of exploited fish populations has never been greater. The models presented in this work show how dynamical systems models that utilize both discrete and continuous mathematical components can be utilized to determine the sensitivity of important metrics of exploited fish stocks including the age distribution, spawning stock abundance, yield, and catch, to assumptions about maturity, longevity, predation rates, interconnectivity, and the spatial, age, and temporal distribution of fishing and natural mortality rates. Long-lived and early-maturing species are most susceptible to assumptions regarding the age distribution of natural and fishing mortality rates. In a system in which both the predator and prey are harvested, combined fishery yield is shown to be positively correlated with management policies in which fishing before annual spawning events is minimized. Combined fishery yield is weakly sensitive to assumptions about the magnitude of attack rates. Finally, a case study showed that the age distribution and catch of large adult fish is strongly sensitive to assumptions about within-stock movement rates, the age-distribution of fishing and natural mortality, and less so assumptions about juvenile survivorship in a combined artisanal and sport fishery. These results show how these combined models can be a powerful tool in the study of age, spatial, and temporal structures of exploited marine fish populations.