The ANZIAM Journal

Research Article

Harvesting in a two-prey one-predator fishery: a bioeconomic model

T. K. Kara1 and K. S. Chaudhuria2

a1 Department of Mathematics, B.E. College (Deemed University), Howrah 711103, India; e-mail:

a2 Department of Mathematics, Jadavpur University, Calcutta 700032, India; e-mail:


A multispecies harvesting model with interference is proposed. The model is based on Lotka-Volterra dynamics with two competing species which are affected not only by harvesting but also by the presence of a predator, the third species. In order to understand the dynamics of this complicated system, we choose to model the simplest possible predator response function in which the feeding rate of the predator increases linearly with prey density. We derive the conditions for global stability of the system using a Lyapunov function. The possibility of existence of a bioeconomic equilibrium is discussed. The optimal harvest policy is studied and the solution is derived in the equilibrium case using Pontryagin's maximal principle. Finally, some numerical examples are discussed.

(Received June 22 2001)

(Revised September 20 2002)