Positive periodic solutions of delayed Nicholson’s blowflies models with a nonlinear density-dependent mortality term

This paper is concerned with the periodic solutions for a new fishery model with a nonlinear density-dependent mortality term, which is a generalization of the classical Nicholson’s blowflies model. By using coincidence degree theory, some criteria are obtained to guarantee that the existence of positive periodic solutions of the model. Moreover, an example and its numerical simulation are given to illustrate our main results.