11.5. Model Results
223
Higher values for adult crab carrying capacity and success rates of eggs
lead to larger steady-state po pulation sizes. Figure 11.6 shows total adult
crab popul ations for carrying capacities varying between 1 and 5 million ,
and Figure 11.7 shows total crab population sizes for success rates between
1"10 - 5 and 3'10- 5 .
The bird fitness relation is altered to determine horseshoe crab population impacts of different fitness scenarios. None of the different scenarios
have significant impact the adult crab pop ulation , but do affect overall
shorebird populations. Figure 11.8 shows resulting bird population size if
the number of eggs required for successful migration and breeding varies
between 100,000 and 500,000.
Lower death rates lead to higher bird populati on sizes. None of the resulting steady-state bird popul ations, however, have a noticeable impact on
adult horseshoe crab popul ations.
11.5. Model Results
Our discussion of mod el results is based on parameters and initial values
described in Section 11.3. Figures 11.9 and 11.10 show, respectively, the
population dynamics of adult crabs and shorebirds when exploitation rates
by the eel fishery are varied, in equal increments, between 0 and .20. Figures 11.11 and 11.12 show effects of the conch fishery for EXPLOITATION
1: BIRDS
1: 200000o .00
----··---l--------- ._-2: BIRDS
3: BIRDS
5[ - - 5
4: BIRDS
5: BIRDS
I
5
5-1i- - - - -
- -4 - - - -- -·- -4 = -=- ·- =t !=======;i==i========4===l 4
4
1: 1000000.00
1:
0.00
25.00
75.00
50.00
Seasons
100.00
FIGURE 11.8