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Publication Date



UM campus only

Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PHD)


Marine Biology and Fisheries (Marine)

Date of Defense


First Committee Member

David Die

Second Committee Member

Chris Cosner

Third Committee Member

Donald DeAngelis

Fourth Committee Member

Jerald Ault

Fifth Committee Member

Donald Olson

Sixth Committee Member

Clay Porch


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.


hybrid model; fisheries; age structure; theoretical