“…In a number of bioeconomic and resource‐economic papers (e.g., Baker, Diele, Marangi, Martiradonna, & Ragni, ; Ding & Lenhart, ; Fister & Lenhart, ; Fister, ; Kelly, Xing, & Lenhart, ; Lenhart, Liang, & Protopopescu, ), the existence of OCs, and subsequently the validity of the Pontryagin's maximum principle, has been proven on a case by case basis using some minimizing sequence and compactness arguments (see also Aniţa et al, , chapter 5; Lenhart & Workman, , chapter 25). However, all these studies consider steady problems or finite time horizons.…”