In this article, we seek to highlight that the increase of the carrying capacity of marine species does not always lead to an increase on the catch levels and on the incomes. To effectively support the theoretical outcomes, we take a bioeconomic model of several seiners exploiting Sardina pilchardus, Engraulis encrasicolus and Xiphias gladius marine species in the Atlantic coast of Morocco based on the parameters given by 'Institut National de Recherche Halieutique' INRH.