384
17. An Age-structured Model of Fish Population Enhancement
Financial Flow Sector
1. The initial loan amount is an estimate of the cost of construction a fish
hatchery and has been set at $1,000,000 for the simulation.
2. Interest Rate is the annual rate of interest charged on the outstanding
debt and was set at 10%, or 0.10.
3. Cost per Fish reflects the hatchery costs of raising the fish until their release. Without actual knowledge of species-specific and hatcheryspecific production costs, this figure is difficult to realistically estimate.
The value was initially set at $1 per fish, which is a reported value for
salmon production in the state of Maine (Wilson et al. 1998).
4. The Price per Fish is the price the fisherman would receive for his catch
expressed in the comparable units to the catch weight. In this simulation, it was set at $2.20 per kilogram.
17.7. Model Resu Its
The results of the model show a consistent pattern of successful population
enhancement, cost recovery and ultimate positive net profit for marine fish
population enhancement based on the fecundity and growth of Atlantic
cod when hatchery-reared fish are introduced into an ecosystem that is
below its carrying capacity. In the simulation described here , the time for
net profits to first become positive was in year 22 after introducing 100,000
hatchery-reared fish per year for ten years. This is based on an initial debt
of $1,000,000 that was borrowed to construct the hatchery, the annual cost
of production of the fish for release, and the assessment of a hatchery tax
on the catch.
The hatchery-reared fish experience substantial mortality over time, beginning with a behavioral mortality because newly released animals have a
behavioral deficit when first released into the wild. Once the fish that survive enter the reproductive pool of mature fish, they contribute to the production of natural age 1 fish, effectively restarting the population of fish
(Figure 17.3). This population does show substantial variability over the
course of the simulation, but it is self-sustaining. This variability is effectively the result of density-dependent mortality rates on the different lifehistory stages as they increase in number and approach their carrying capacity, as defined in the model. Despite relatively high rates of mortality
throughout the life history of the fish (all of which can be altered in simulations to evaluate their impact), the population of fish available to the
fishery increases the total catch , and the value of these fish offsets the
debt.
The addition of hatchery-reared animals re-establishes the population, although there is often a substantial lag-time before there is complete cost recovery and positive profit. Depending on the mortality rates for the differ-
17. An Age-structured Model of Fish Population Enhancement
Financial Flow Sector
1. The initial loan amount is an estimate of the cost of construction a fish
hatchery and has been set at $1,000,000 for the simulation.
2. Interest Rate is the annual rate of interest charged on the outstanding
debt and was set at 10%, or 0.10.
3. Cost per Fish reflects the hatchery costs of raising the fish until their release. Without actual knowledge of species-specific and hatcheryspecific production costs, this figure is difficult to realistically estimate.
The value was initially set at $1 per fish, which is a reported value for
salmon production in the state of Maine (Wilson et al. 1998).
4. The Price per Fish is the price the fisherman would receive for his catch
expressed in the comparable units to the catch weight. In this simulation, it was set at $2.20 per kilogram.
17.7. Model Resu Its
The results of the model show a consistent pattern of successful population
enhancement, cost recovery and ultimate positive net profit for marine fish
population enhancement based on the fecundity and growth of Atlantic
cod when hatchery-reared fish are introduced into an ecosystem that is
below its carrying capacity. In the simulation described here , the time for
net profits to first become positive was in year 22 after introducing 100,000
hatchery-reared fish per year for ten years. This is based on an initial debt
of $1,000,000 that was borrowed to construct the hatchery, the annual cost
of production of the fish for release, and the assessment of a hatchery tax
on the catch.
The hatchery-reared fish experience substantial mortality over time, beginning with a behavioral mortality because newly released animals have a
behavioral deficit when first released into the wild. Once the fish that survive enter the reproductive pool of mature fish, they contribute to the production of natural age 1 fish, effectively restarting the population of fish
(Figure 17.3). This population does show substantial variability over the
course of the simulation, but it is self-sustaining. This variability is effectively the result of density-dependent mortality rates on the different lifehistory stages as they increase in number and approach their carrying capacity, as defined in the model. Despite relatively high rates of mortality
throughout the life history of the fish (all of which can be altered in simulations to evaluate their impact), the population of fish available to the
fishery increases the total catch , and the value of these fish offsets the
debt.
The addition of hatchery-reared animals re-establishes the population, although there is often a substantial lag-time before there is complete cost recovery and positive profit. Depending on the mortality rates for the differ-