function [dxdt]=fishery0(t,x)
%Simulation of a fishery
global a b c r K k ki kt xr0
r=0.2;K=100;a=0.1;b=1;c=1;
k=0.5;ki=0.5;kt=0.5;
f=r*x(1)*(1-x(1)/K);
xr0=c/a/b;
if x(1)>xr0+3,
    u=3;
else
    u=x(1)-xr0;
end
h=a*x(1)*u;
g=b*h-c*u;
dxdt=[f-h];
