In this paper, we investigate an optimal harvesting problem of a spatially explicit fishery model that was previously analyzed. On the surface, this problem looks innocent, but if parameters are set to where a singular arc occurs, two complex questions arise. The first question pertains to Fuller's phenomenon (or chattering), a phenomenon in which the optimal control possesses a singular arc that cannot be concatenated with the bang-bang arcs without prompting infinite oscillations over a finite region. 1) How do we numerically assess whether or not a problem chatters in cases when we cannot analytically prove such a phenomenon? The second question focuses on implementation of an optimal control. 2) When an optimal control has regions that are difficult to implement, how can we find alternative strategies that are both suboptimal and realistic to use? Although the former question does not apply to all optimal harvesting problems, most fishery managers should be concerned about the latter. Interestingly, for this specific problem, our techniques for answering the first question results in an answer to the the second. Our methods involve using an extended version of the switch point algorithm (SPA), which handles control problems having initial and terminal conditions on the states. In our numerical experiments, we obtain strong empirical evidence that the harvesting problem chatters, and we find three alternative harvesting strategies with fewer switches that are realistic to implement and near optimal.
Citation: Summer Atkins, William W. Hager, Maia Martcheva. The switch point algorithm applied to a harvesting problem[J]. Mathematical Biosciences and Engineering, 2024, 21(5): 6123-6149. doi: 10.3934/mbe.2024269
In this paper, we investigate an optimal harvesting problem of a spatially explicit fishery model that was previously analyzed. On the surface, this problem looks innocent, but if parameters are set to where a singular arc occurs, two complex questions arise. The first question pertains to Fuller's phenomenon (or chattering), a phenomenon in which the optimal control possesses a singular arc that cannot be concatenated with the bang-bang arcs without prompting infinite oscillations over a finite region. 1) How do we numerically assess whether or not a problem chatters in cases when we cannot analytically prove such a phenomenon? The second question focuses on implementation of an optimal control. 2) When an optimal control has regions that are difficult to implement, how can we find alternative strategies that are both suboptimal and realistic to use? Although the former question does not apply to all optimal harvesting problems, most fishery managers should be concerned about the latter. Interestingly, for this specific problem, our techniques for answering the first question results in an answer to the the second. Our methods involve using an extended version of the switch point algorithm (SPA), which handles control problems having initial and terminal conditions on the states. In our numerical experiments, we obtain strong empirical evidence that the harvesting problem chatters, and we find three alternative harvesting strategies with fewer switches that are realistic to implement and near optimal.
[1] | M. Demir, S. Lenhart, A spatial food chain model for the Black Sea anchovy, and its optimal fishery, Discrete Contin. Dyn. Syst., 26 (2021), 155–171. https://doi.org/10.3934/dcdsb.2020373 doi: 10.3934/dcdsb.2020373 |
[2] | R. Hilborn, Overfishing: What Everyone Needs to Know, Oxford University Press, Oxford, 2012. |
[3] | M. R. Kelly, Y. Xing, S. Lenhart, Optimal fish harvesting for a population modeled by a nonlinear parabolic partial differential equation, Nat. Resour. Model., 29 (2016), 36–70. https://doi.org/10.1111/nrm.12073 doi: 10.1111/nrm.12073 |
[4] | G. N. Tuck, H. P. Possingham, Marine protected areas for spatially structured exploited stocks, Marine Ecology Progress Series, 192 (2000), 81–101. https://doi.org/10.3354/meps192089 doi: 10.3354/meps192089 |
[5] | J. N. Sanchirico, J. E. Wilen, Bioeconomics of spatial exploitation in a patchy environment, J. Environ. Econ. Manage., 37 (1999), 129–150. https://doi.org/10.1006/jeem.1998.1060 doi: 10.1006/jeem.1998.1060 |
[6] | J. N. Sanchirico, J. E. Wilen, A bioeconomic model of marine reserve creation, J. Environ. Econ. Manage., 42 (2001), 257–276. https://doi.org/10.1006/jeem.2000.1162 doi: 10.1006/jeem.2000.1162 |
[7] | G. Brown, J. Roughgarden, A metapopulation model with private property and a common pool, Ecol. Econ., 30 (1997), 65–71. https://doi.org/10.1016/S0921-8009(97)00564-8 doi: 10.1016/S0921-8009(97)00564-8 |
[8] | C. W. Clark, The Worldwide Crises in Fisheries, Cambridge University Press, New York, 2006. |
[9] | C. J. Walter, S. Martell, Fisheries Ecology Management, Princeton University Press, Princeton, New Jersey, 2004. |
[10] | T. Quinn Ⅱ, Ruminations on the development and future of population dynamic models in fisheries, Nat. Res. Model, 16 (2003), 341–392. https://doi.org/10.1111/j.1939-7445.2003.tb00119.x doi: 10.1111/j.1939-7445.2003.tb00119.x |
[11] | J. E. Wilen, Spatial management of fisheries, Marine Resour. Econ., 19 (2004), 7–19. https://doi.org/10.1086/mre.19.1.42629416 doi: 10.1086/mre.19.1.42629416 |
[12] | M. Neubert, Marine reserves and optimal harvesting, Ecol. Lett., 6 (2003), 843–849. https://doi.org/10.1046/j.1461-0248.2003.00493.x doi: 10.1046/j.1461-0248.2003.00493.x |
[13] | M. Neubert, G. Herrera, Triple benefits from spatial resource management, Theor. Ecol., 1 (2008), 5–12. https://doi.org/10.1007/s12080-007-0009-6 doi: 10.1007/s12080-007-0009-6 |
[14] | W. Ding, S. Lenhart, Optimal harvesting of a spatially explicit fishery model, Nat. Resour. Model., 22 (2009), 173–211. https://doi.org/10.1111/j.1939-7445.2008.00033.x doi: 10.1111/j.1939-7445.2008.00033.x |
[15] | H. Joshi, G. Herrera, S. Lenhart, M. Neubert, Optimal dynamic harvest of a mobile renewable resource, Nat. Resour. Model., 22 (2009), 322–343. https:/doi.org/10.1111/j.1939-7445.2008.00038.x doi: https:/doi.org/10.1111/j.1939-7445.2008.00038.x |
[16] | P. De Leenheer, Optimal placement of marine protected areas: A trade-off between fisheries goals and conservation efforts, IEEE Trans. Autom. Control, 59 (2014), 1583–1587. https:/doi.org/10.1109/TAC.2013.2292742 doi: https:/doi.org/10.1109/TAC.2013.2292742 |
[17] | M. R. Kelly, M. G. Neubert, S. Lenhart, Marine reserves and optimal dynamic harvesting when fishing damages habitat, Theor. Ecol., 12 (2019), 131–144. https://doi.org/10.1007/s12080-018-0399-7 doi: 10.1007/s12080-018-0399-7 |
[18] | M. Demir, S. Lenhart, Optimal sustainable fishery management of the Black Sea anchovy with food chain modeling framework, Nat. Resour. Model., 33 (2020), 1–29. https://doi.org/10.1111/nrm.12253 doi: 10.1111/nrm.12253 |
[19] | H. Schättler, U. Ledzewicz, Geometric Optimal Control, Springer, 2012. https://doi.org/10.1007/978-1-4614-3834-2 |
[20] | M. I. Zelikin, V. Borisov, Theory of Chattering Control: With Applications to Astronautics, Robotics, Economics, and Engineering, Birkhäuser, 1994. https://doi.org/10.1007/978-1-4612-2702-1 |
[21] | H. J. Kelley, R. Kopp, H. G. Moyer, 3 Singular extremals, Math. Sci. Eng., 31 (1967), 63–101. https://doi.org/10.1016/S0076-5392(09)60039-4 doi: 10.1016/S0076-5392(09)60039-4 |
[22] | R. M. Lewis, Definitions of order and junction conditions in singular optimal control problems, SIAM J. Control Optim., 18 (1980), 21–32. https://doi.org/10.1137/0318002 doi: 10.1137/0318002 |
[23] | W. W. Hager, Extension of switch point algorithm to boundary-value problems, Comput. Optim. Appl., 86 (2023), 1229–1246. https://doi.org/10.1007/s10589-023-00530-y doi: 10.1007/s10589-023-00530-y |
[24] | M. Aghaee, W. W. Hager, The switch point algorithm, SIAM J. Control Optim., 59 (2021), 2570–2593. https://doi.org/10.1137/21M1393315 doi: 10.1137/21M1393315 |
[25] | M. Schaefer, Some considerations of population dynamics and economics in relation to the management of commercial marine fisheries, J. Fish. Res. Board Can., 14 (1957), 669–681. https://doi.org/10.1139/f57-025 doi: 10.1139/f57-025 |
[26] | C. W. Clark, Mathematical Bioeconomics: The Optimal Management of Renewable Resources, Wiley, New York, 1990. |
[27] | R. A. Fisher, The wave of advance of advantageous genes, Eugenics, 7 (1937), 355–369. https://doi.org/10.1111/j.1469-1809.1937.tb02153.x doi: 10.1111/j.1469-1809.1937.tb02153.x |
[28] | A. Cañada, J. L. Gámez, J. A. Montero, Study of an optimal control problem for diffusive nonlinear elliptic equations of logistic type, SIAM J. Control Optim., 36 (1998), 1171–1189. https://doi.org/10.1137/S0363012995293323 doi: 10.1137/S0363012995293323 |
[29] | J. A. Montero, A uniqueness result for an optimal control problem on a diffusive elliptic Volterra-Lotka type equation, J. Math. Anal. Appl., 243 (2000), 13–31. https://doi.org/10.1006/jmaa.1999.6638 doi: 10.1006/jmaa.1999.6638 |
[30] | H. Berestycki, P. L. Lions, Some applications of the method of super and subsolutions, in Bifurcation and Nonlinear Eigenvalue Problems. Lecture Notes in Mathematics (eds. C. Bardos, J. M. Lasry and M. Schatzman), Springer Berlin Heidelberg, (1980), 16–41. https://doi.org/10.1007/BFb0090426 |
[31] | N. V. Krylov, Nonlinear Elliptic and Parabolic Equations of the Second Order, D. Reidel Publishing Company, Dordrecht, Holland, (1987). https://doi.org/10.1007/978-94-010-9557-0 |
[32] | U. Ledzewicz, H. Schättler, Singular controls and chattering arcs in optimal control problems arising in biomedicine, Control Cybern., 38 (2009), 1501–1523. |
[33] | J. P. McDanell, W. F. Powers, Necessary conditions for joining optimal singular and nonsingular subarcs, SIAM J. Control, 9 (1971), 161–173. https://doi.org/10.1137/0309014 doi: 10.1137/0309014 |
[34] | S. Atkins, Regularization of Singular Control Problems that Arise in Mathematical Biology, PhD thesis, University of Florida, 2021. |
[35] | W. W. Hager, H. Zhang, Algorithm 1035: A gradient-based implementation of the polyhedral active set algorithm, ACM Trans. Math. Software, 49 (2023), 1–13. https://doi.org/10.1145/3583559 doi: 10.1145/3583559 |
[36] | W. W. Hager, H. Zhang, An active set algorithm for nonlinear optimization with polyhedral constraints, Sci. Chin. Math., 59 (2016), 1525–1542. https://doi.org/10.1007/s11425-016-0300-6 doi: 10.1007/s11425-016-0300-6 |
[37] | S. Atkins, M. Aghaee, M. Martcheva, W. W. Hager, Solving singular control problems in mathematical biology using PASA, in Computational and Mathematical Population Dynamics (eds. N. Tuncer, M. Martcheva, O. Prosper and L. Childs), World Scientific, (2023), 319–419. https://doi.org/10.1142/9789811263033_0009 |
[38] | M. Caponigro, R. Ghezzi, B. Piccoli, E. Trelat, Regularization of chattering phenomena via bounded variation controls, IEEE Trans. Autom. Control, 63 (2018), 2046–2060. https://doi.org/10.1109/TAC.2018.2810540 doi: 10.1109/TAC.2018.2810540 |