Seasonal closure and minimum legal size for barramundi in the Gulf ...

Relative proportion
1
0.8
Commercial yield
0.6
Scenario1 0.8
Scenario2
Scenario3
0.79
0.4
Scenario4 0.78
Scenario5
0.2
Scenario6
0.77
Scenario7 0.76
Scenario8
0
0 0.5 1 1.5 2
1.85 1.86 1.87 1.88 1.89 1.9
F
F
Figure 2 The relative commercial yield shown as proportion scaled to 1 at the maximum
yield (F=0.7985, Scenario 7)
Recreational yield
Zoom
1
1
0.82
0.81
Zoom
Relative proportion
0.8
0.6
0.4
0.2
Scenario1
Scenario2
Scenario3
Scenario4
Scenario5
Scenario6
Scenario7
Scenario8
0 0.5 1 1.5 2
F
Figure 3
0.95
0.9
0.85
1.6 1.7 1.8 1.9
F
The relative recreational yield shown as proportion scaled to 1 at the maximum
yield (F=1.8971, Scenario 5)
Spawning per recruit
Total number of eggs per recruit was higher with a four-month closure than a threemonth
closure and this difference became larger with greater fishing pressure (Figure
4).
Figure 5 shows the ratio of the spawning index with a three-month closure to the
index with a four-month closure. With the highest F applied in the model (F =1.8971 ~
85% harvest rate), the spawning stock would be about 30% lower with a three-month
closure than with a four-month closure. Under moderate to high fishing pressure (F =
0.4308 to 0.7985 ~ 35–55% harvest rate), the spawning index would be about 15%
lower with a three-month closure.
Reducing the minimum legal size to 58 cm resulted in up to 3% less abundance of
mature males and up to 3% less egg production (under the assumption of constant
recruitment though time).
Technical report prepared for the Gulf finfish review. Not government policy. 15