14.4. Results
321
cod, pollock and haddock populations on Georges Bank. The choice of the
respective parameters can be readily changed to reflect different assumptions, or new insight into the biology of the three fishes and their interaction.
14.4. Results
Given initial conditions on fishing effort, population sizes and distribution,
as well as parameters characterizing the responsiveness of fishermen and
fish populations, the dynamic multispecies fisheries model yields a variety
of possible development paths . The first scenario is run in the absence of
additional management policies and assesses the implications of technological improvements alone in the fishing industry. Such improvements may
affect gear, boats and other equipment used to locate and catch fish. The
anticipated effect of technical change is to increase the catchabllity of fish
on Georges Bank. For simplicity, population effects on changes in catchability are not taken into account. For the model , we assume exogenously
given technical change to increase the catchability coefficient at an annual
rate of 3%. The resulting changes in Georges Bank biomass and catch are
given in Figure 14.1. Following technical change and a slight increase in
population sizes during the early 1990s, catch is stimulated , resulting in increased profits and further increases in effort beyond the time at which
population sizes drop drastically. Initial temporary adjustments in effort and
decreases in catch are ultimately followed by a period of sustained increases in catch. The long-term increase in catch is due to the increased effectiveness of a unit of effort.
600.00
-
§ '"
g
- '-'
-
"0
'" 1"--..
-c,__- 1.
'1
i
CiS
I
2010
Year
2030
2020
2000
0.00
1990
FIGURE
321
cod, pollock and haddock populations on Georges Bank. The choice of the
respective parameters can be readily changed to reflect different assumptions, or new insight into the biology of the three fishes and their interaction.
14.4. Results
Given initial conditions on fishing effort, population sizes and distribution,
as well as parameters characterizing the responsiveness of fishermen and
fish populations, the dynamic multispecies fisheries model yields a variety
of possible development paths . The first scenario is run in the absence of
additional management policies and assesses the implications of technological improvements alone in the fishing industry. Such improvements may
affect gear, boats and other equipment used to locate and catch fish. The
anticipated effect of technical change is to increase the catchabllity of fish
on Georges Bank. For simplicity, population effects on changes in catchability are not taken into account. For the model , we assume exogenously
given technical change to increase the catchability coefficient at an annual
rate of 3%. The resulting changes in Georges Bank biomass and catch are
given in Figure 14.1. Following technical change and a slight increase in
population sizes during the early 1990s, catch is stimulated , resulting in increased profits and further increases in effort beyond the time at which
population sizes drop drastically. Initial temporary adjustments in effort and
decreases in catch are ultimately followed by a period of sustained increases in catch. The long-term increase in catch is due to the increased effectiveness of a unit of effort.
600.00
-
§ '"
g
- '-'
-
"0
'" 1"--..
-c,__- 1.
'1
i
CiS
I
2010
Year
2030
2020
2000
0.00
1990
FIGURE