17.6. Model Input Values
383
following is a listing of the input variables for the simulations presented
here for the different sectors in the model and documentation as to the
source of the information.
Hatchery sector
1. Fish Raised should be set to represent a realistic value for the hatchery
REARING of juvenile fish that will depend on the specific hatchery design. It has been arbitrarily set at an annual production of 100,000 fish
for this simulation .
2. Behavioral Mortality is the percent loss of hatchery-reared fish upon their
release and prior to their adapting to the conditions in the natural environment. The input value of 18%, or 0.18, has been selected for the simulation and is an estimated value .
Life History Sector
1. Catch Rate is the percentage of fish from the population that is removed
annually. It can be varied to evaluate the impact of fishing on POPULATION recovery, but has initially been set at 60%, or 0.60.
2. Immigration Rate is the percentage of fish that leave the population annually and is an estimated value at 3%, or 0.03.
3. Mortality Age 0 is the rate of mortality for larval fish and has been set at
99.95 %, or 0.9995.
4. Mortality Age 1 is the rate of natural mortality experienced by age 1 fish
and is a graphic function of the sum of the numbers of mature fish. It
ranges from 80%, or 0.80, to 99.9%, or 0.99, as the sum of mature fish increases from 0 to 5,000,000.
5. Mortality Age 2 is the rate of natural mortality experienced by age 2 fish
and, like the mortality on age 1 fish, it is a graphic function of the sum of
mature fish over the range of 0 to 5,000,000. The mortality rate over this
range is 40%, or 0.40, to 100%, or 1.00.
6. Mortality Matures is the rate of natural mortality experienced by age 3
and older fish, and is also a graphic function of the number of mature
fish. In this case, the mortality rate remains constant at 20%, or .20, over
a large increase in the population size, but does increase to 100% as the
population ultimately grows to 1,000,000,000 fish.
7. Weight at Age for Atlantic cod was taken from Wilson et al. 1998 and/or
Serchuk et al. 1994. The weights for a given age, expressed in the model
in grams, would not normally be changed unless the species being investigated were changed, although there is intraspecific regional and temporal variation in these values (see Hislop et al. 1978; Waiwood 1982)
8. Fecundity is also a weight- and age-dependent function and has been incorporated in the model in accordance with a weight-fecundity relation
for Atlantic cod (Powles 1958), which can vary with both location and
over time (Wrobleski et al. 1998).
383
following is a listing of the input variables for the simulations presented
here for the different sectors in the model and documentation as to the
source of the information.
Hatchery sector
1. Fish Raised should be set to represent a realistic value for the hatchery
REARING of juvenile fish that will depend on the specific hatchery design. It has been arbitrarily set at an annual production of 100,000 fish
for this simulation .
2. Behavioral Mortality is the percent loss of hatchery-reared fish upon their
release and prior to their adapting to the conditions in the natural environment. The input value of 18%, or 0.18, has been selected for the simulation and is an estimated value .
Life History Sector
1. Catch Rate is the percentage of fish from the population that is removed
annually. It can be varied to evaluate the impact of fishing on POPULATION recovery, but has initially been set at 60%, or 0.60.
2. Immigration Rate is the percentage of fish that leave the population annually and is an estimated value at 3%, or 0.03.
3. Mortality Age 0 is the rate of mortality for larval fish and has been set at
99.95 %, or 0.9995.
4. Mortality Age 1 is the rate of natural mortality experienced by age 1 fish
and is a graphic function of the sum of the numbers of mature fish. It
ranges from 80%, or 0.80, to 99.9%, or 0.99, as the sum of mature fish increases from 0 to 5,000,000.
5. Mortality Age 2 is the rate of natural mortality experienced by age 2 fish
and, like the mortality on age 1 fish, it is a graphic function of the sum of
mature fish over the range of 0 to 5,000,000. The mortality rate over this
range is 40%, or 0.40, to 100%, or 1.00.
6. Mortality Matures is the rate of natural mortality experienced by age 3
and older fish, and is also a graphic function of the number of mature
fish. In this case, the mortality rate remains constant at 20%, or .20, over
a large increase in the population size, but does increase to 100% as the
population ultimately grows to 1,000,000,000 fish.
7. Weight at Age for Atlantic cod was taken from Wilson et al. 1998 and/or
Serchuk et al. 1994. The weights for a given age, expressed in the model
in grams, would not normally be changed unless the species being investigated were changed, although there is intraspecific regional and temporal variation in these values (see Hislop et al. 1978; Waiwood 1982)
8. Fecundity is also a weight- and age-dependent function and has been incorporated in the model in accordance with a weight-fecundity relation
for Atlantic cod (Powles 1958), which can vary with both location and
over time (Wrobleski et al. 1998).