Visiting lecturer: Abdul-Aziz Yakubu

Abdul-Aziz Yakubu is a Professor of Mathematics at Howard University where he currently serves as chair of the mathematics department. Yakubu is trained as an applied mathematician and has worked on mathematical biology problems since the 1990s. His research investigations focus on nonlinear systems that arise in the diverse fields of ecology, epidemiology and demography. Several of Yakubu's research projects focus on population and disease dynamics. Specifically, these include studies of the dynamics of species interactions (such as competition, predator-prey, food chain, etc.) in constant and periodic environments. He has done additional research on the impact of subpopulation linkages on the stability and resilience of exploited fisheries. More recently, Yakubu has expanded his research to include how various intermittent preventative treatments affect the incidence of clinical malaria in Africa.

Yakubu will lecture on The Impact of Periodic Proportional Harvesting Policies on Total Allowable Catch (TAC)-Regulated Fishery Systems. Fishery systems throughout the world are in crisis and his lecture will compare the effects of periodic fishing (pulse fishing) on TAC stock dynamics with those of constant fishing strategies. Yakubu will show that periodic harvesting strategies can effectively stabilize complex dynamics caused by overcompensation. Under specific conditions related to the Allee effect, he will show that both strategies can to lead to a sudden collapse of TAC regulated fisheries. To demonstrate this in real fishery systems, Yakubu will apply the mathematical model framework to Gulf of Alaska Pacific halibut data from the International Pacific Halibut Commission (IPHC) annual reports and Georges Bank Atlantic cod data from the North East Fisheries Science Center (NEFSC) Reference Document 08-15. Finally, he will use the mathematical model to show that TAC is an effective policy for preventing the collapse of halibut. However, of note is that the model predicts that cod is endangered. Furthermore, he will demonstrate that the likelihood of the collapse of both halibut and cod increase with increased weather variability. The mathematical model framework could be useful for future investigations on the sustainability of other exploited fishery systems.