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6. Spatial Fisheries Model
1: N v. N DOT
10000.00
-5000 .00
1\
\
\0
/
I
t)
Q
:z;
-20000.00
40000.00
0.00
20000.00
N
FIGURE 6.16
Notice that the presence of a reserve and movement across the reservefishery boundary does not imply stabilization of the population dynamics in
all cases. Figure 6.16 shows an extreme case in which the reserve supplies
individuals to its surroundings but none of the fish in the fishery visit the reserve , i.e. M; = M 2 = M 3 = 0 and M 4 = .8. In this case, population begins to
slowly expand-and continues to do so in the long run-after it has settled
down to a level much lower than the starting point.
Experiment with this model. Choose different movement rates for fish in
different regions and different carrying capacities (unclick the "Apply to All"
button in the arrays for M ; and K) , and assume different values for ALPHA.
Each time before you run the model, think what the results may be , and
then carefully explore why the results matched (or did not match) your
expectations.
SPATIAL FISHERY WITH RESERVE
E(t) = E(t-dt) + (E_DOT) * dt
INIT E = 20000