Research Article Bioeconomic-Epidemiological Model of Scomber colias Population in the Moroccan Coasts Nossaiba Baba, Imane Agmour, Yousef El Foutayeni , and Naceur Achtaich Analysis, Modeling and Simulation Laboratory, Hassan II University of Casablanca, Morocco Correspondence should be addressed to Yousef El Foutayeni; foutayeni@gmail.com Received 25 August 2020; Revised 28 January 2021; Accepted 22 February 2021; Published 20 March 2021 Academic Editor: Fernando Sim es Copyright © 2021 Nossaiba Baba et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this paper, we develop and study a mathematical model for the dynamics of Scomber colias and Thunnus thynnus prey-predator with parasitic helminths. We search to analyze a bioeconomic model in which both susceptible and infected prey populations Scomber colias are exposed to the predator Thunnus thynnus, with varying degrees of exposure. However, the predator feeds preferentially on the most numerous prey types. This implies a kind of switching from the susceptible class to the infected class, and vice versa, as these two types of prey change in numerical superiority. So, the positivity, boundedness, equilibria, stability, and bioeconomic equilibrium are studied. Some numerical simulation of stability is cited. For giving a high yield and keeping the Scomber colias and Thunnus thynnus populations away from extension, we use the Maximum Principle of Pontryagin. 1. Introduction Morocco is one of the largest fish producers in the world, according to the 2018 report from the Food and Agricul- ture Organization of the United Nations (FAO). In 2018, national fishery production totaled 1371683 tons for a turnover of 11579544 thousand MAD (Moroccan Dir- hams). The export volume reached more than 722921 tons for a turnover of 22,531 million MAD (DPM, 2018) [1]. A study published in December 2019 reveals that the main reason for the repression of Moroccan fish is the presence of parasites. The study was carried out by the Hassan II Agronomic and Veterinary Institute (HAVI) and the cen- ter specializing in the pathology of aquatic animals at the National Fisheries Research Institute (NFRI). The parasites are the source of major problems with natural fish stocks. Indeed, the parasites determine pathologies slowing the growth and increasing the mortality of their hosts and constitute, consequently, a limiting factor of the success of the productivity in aquaculture. Following the analysis concerning 1678 pieces of fish of different species, 537 of which come from the Atlantic (port of Essaouira and wholesale market of Casablanca) and 1141 pieces from the Mediterranean, the extent of parasitism is almost the same on the Mediterranean coast (31.1%) and the Atlantic (32%). Nematodes (anisakis + acanthocephalans) occupy most of the parasites in the Atlantic and the Mediterranean, with respective prevalence of 21.4% and 24.9%. The plerocer- coid larva of the cestode was found in silver saber, with a prevalence of 8.3% at the Atlantic level, as is shown in Figure 1. It should be noted that to be contaminated, the fish must feed on plants or animals carrying parasites. In fact, several animal species can carry parasites and contaminate the fish’s environment through their excrement, which some- times contains parasite eggs. To develop, these eggs will infect plankton, small crustaceans, snails, etc. If fish eat these organisms, they in turn can carry parasites. These reasons encouraged us to study this phenomenon and to see all the interactions that occur between populations of fish. In this context, many mathematical models have been developed to describe the dynamics of fisheries, and we can refer, for example, [2–7]. Moreover, we can cite [8], in this work, the Hindawi Journal of Applied Mathematics Volume 2021, Article ID 8892388, 22 pages https://doi.org/10.1155/2021/8892388