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• 1. [Article] An Ecological-Economic Simulation Model of Genetic interaction Between Farmed and Wild Salmon

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: An Ecological-Economic Simulation Model of Genetic interaction Between Farmed and Wild Salmon Author: Hindar, Kjetil, Liu, Yajie, Skonhoft, Anders, Diserud, Ola Abstract only. Title: An Ecological-Economic Simulation Model of Genetic interaction Between Farmed and Wild Salmon Author: Hindar, Kjetil, Liu, Yajie, Skonhoft, Anders, Diserud, Ola Abstract only. Close

• 2. [Article] Generalization of Age-Structured Models in Theory and Practice

  A generalization of the harvesting functions and the stock updating functions in age-structured bioeconomic models is outlined. Using this generalization everything from completely uniformly distributed ...

  Citation × Citation Citation Abstract Copy Title: Generalization of Age-Structured Models in Theory and Practice Author: Steinshamn, Stein Ivar A generalization of the harvesting functions and the stock updating functions in age-structured bioeconomic models is outlined. Using this generalization everything from completely uniformly distributed fish to extreme schooling is taken care of. The classical Beverton-Holt model comes out as a special case of the generalized model. Both the theoretical outline as well as practical numerical examples are provided, and the generalization can be applied both for simulation as well as optimization purposes given appropriate software. Here we apply advanced non-linear programming to maximize the net present value in a bioeconomic setting where the new updating and harvesting functions are used as constraints. This is possible thanks to new software, such as KNITRO, for solving highly nonlinear problems. Applications of this generalized model produce interesting new results. One such practical result is that pulse fishing seems to become less and less economically profitable as we move from uniformly distributed fish to schooling species. The main reason why pulse fishing cease to be optimal in schooling fisheries, is that the economies of scale present in search fisheries gradually disappear when we move from search fisheries to schooling fisheries. This may have important implications for how fish stocks ought to be managed in the future, especially with respect to total allowable catches based on bioeconomic criteria. Title: Generalization of Age-Structured Models in Theory and Practice Author: Steinshamn, Stein Ivar A generalization of the harvesting functions and the stock updating functions in age-structured bioeconomic models is outlined. Using this generalization everything from completely uniformly distributed fish to extreme schooling is taken care of. The classical Beverton-Holt model comes out as a special case of the generalized model. Both the theoretical outline as well as practical numerical examples are provided, and the generalization can be applied both for simulation as well as optimization purposes given appropriate software. Here we apply advanced non-linear programming to maximize the net present value in a bioeconomic setting where the new updating and harvesting functions are used as constraints. This is possible thanks to new software, such as KNITRO, for solving highly nonlinear problems. Applications of this generalized model produce interesting new results. One such practical result is that pulse fishing seems to become less and less economically profitable as we move from uniformly distributed fish to schooling species. The main reason why pulse fishing cease to be optimal in schooling fisheries, is that the economies of scale present in search fisheries gradually disappear when we move from search fisheries to schooling fisheries. This may have important implications for how fish stocks ought to be managed in the future, especially with respect to total allowable catches based on bioeconomic criteria. Close

• 3. [Article] Market-Based Size Selection in the Bering Sea Pollock Fishery

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: Market-Based Size Selection in the Bering Sea Pollock Fishery Author: Haynie, Alan, Ianelli, James Abstract only. Title: Market-Based Size Selection in the Bering Sea Pollock Fishery Author: Haynie, Alan, Ianelli, James Abstract only. Close

• 4. [Article] Bioeconomic Modeling and Management of the Southern Bluefin Tuna Fishery

  The paper reviews the management and bioeconomic modeling of the Southern Bluefin Tuna stock. It describes two studies using simultaneous, non-cooperative, three player games to predict revenue and stock ...

  Citation × Citation Citation Abstract Copy Title: Bioeconomic Modeling and Management of the Southern Bluefin Tuna Fishery Author: Kennedy, John, Campbell, Harry The paper reviews the management and bioeconomic modeling of the Southern Bluefin Tuna stock. It describes two studies using simultaneous, non-cooperative, three player games to predict revenue and stock outcomes generated by a deterministic, discrete, age-structured model of the SBT population. Two versions of the model, corresponding to biological and harvesting conditions prevailing around 2000 and 2007 respectively are considered. Because of a significant downward revision of estimates of the productivity of the SBT stock between these two dates, the later model suggests that conservation and optimal utilization of the SBT stock will require a substantial cut in catch quotas as compared with the results of the earlier model. Title: Bioeconomic Modeling and Management of the Southern Bluefin Tuna Fishery Author: Kennedy, John, Campbell, Harry The paper reviews the management and bioeconomic modeling of the Southern Bluefin Tuna stock. It describes two studies using simultaneous, non-cooperative, three player games to predict revenue and stock outcomes generated by a deterministic, discrete, age-structured model of the SBT population. Two versions of the model, corresponding to biological and harvesting conditions prevailing around 2000 and 2007 respectively are considered. Because of a significant downward revision of estimates of the productivity of the SBT stock between these two dates, the later model suggests that conservation and optimal utilization of the SBT stock will require a substantial cut in catch quotas as compared with the results of the earlier model. Close

• 5. [Article] Lessons From the Collapse of the Stock of Anchovy in the Bay of Biscay

  No poster available.

  Citation × Citation Citation Abstract Copy Title: Lessons From the Collapse of the Stock of Anchovy in the Bay of Biscay Author: Del Valle Erkiaga, Ikerne, Astorkiza, Kepa No poster available. Title: Lessons From the Collapse of the Stock of Anchovy in the Bay of Biscay Author: Del Valle Erkiaga, Ikerne, Astorkiza, Kepa No poster available. Close

• 6. [Article] Optimizing Dynamic Catch Quotas in Stock Fluctuating Fisheries

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: Optimizing Dynamic Catch Quotas in Stock Fluctuating Fisheries Author: Seijo, Juan Carlos Abstract only. Title: Optimizing Dynamic Catch Quotas in Stock Fluctuating Fisheries Author: Seijo, Juan Carlos Abstract only. Close

• 7. [Article] A Spatial Bioeconomic Model of West Indian Ocean Tuna Fisheries. Assessing Mpas Relevance for Highly Migratory Species

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: A Spatial Bioeconomic Model of West Indian Ocean Tuna Fisheries. Assessing Mpas Relevance for Highly Migratory Species Author: Fortilus, Jeanne, Chaboud, Christian Abstract only. Title: A Spatial Bioeconomic Model of West Indian Ocean Tuna Fisheries. Assessing Mpas Relevance for Highly Migratory Species Author: Fortilus, Jeanne, Chaboud, Christian Abstract only. Close

• 8. [Article] Simulation Model Evaluation of Some Fisheries Balance Indicators

  Chronic overcapacity has been identified as a major cause of the overfishing of Europe’s fish stocks and the poor economic performance of the European fishing fleets. Mechanisms are needed to ensure that ...

  Citation × Citation Citation Abstract Copy Title: Simulation Model Evaluation of Some Fisheries Balance Indicators Author: Scott, Robert, Sampson, David Chronic overcapacity has been identified as a major cause of the overfishing of Europe’s fish stocks and the poor economic performance of the European fishing fleets. Mechanisms are needed to ensure that the capacity of European fishing fleets remain proportionate to available fish stocks. To that end, the European Commission developed “Guidelines for an improved analysis of the balance between fishing capacity and fishing opportunities”, which specify a minimum set of fleet-based technical, biological, economic, and social indicators that purportedly measure the balance between fishing fleets and fish resources. A bioeconomic simulation model was developed to assist in the evaluation of some of these balance indicators. The model is age-structured, like standard single-species stock assessment models, but accommodates multiple independent fish stocks that are harvested by multiple independent fishing fleets. The fish stocks occupy multiple spatial regions with diffusion of fish between regions. The fishing fleets choose where and how to fish based on anticipated profits. Randomness is included in the simulated system in the annual fish recruitments and their spatial distribution. The model was used to generate a series of balance indicators that were then compared against the true conditions in the simulated fisheries to evaluate whether the indicators provide accurate signals of system status. The simulations showed that randomness in recruitment propagates directly into randomness in the balance indicators implying that it will be difficult to detect meaningful signals from any short time series of balance indicator values. Title: Simulation Model Evaluation of Some Fisheries Balance Indicators Author: Scott, Robert, Sampson, David Chronic overcapacity has been identified as a major cause of the overfishing of Europe’s fish stocks and the poor economic performance of the European fishing fleets. Mechanisms are needed to ensure that the capacity of European fishing fleets remain proportionate to available fish stocks. To that end, the European Commission developed “Guidelines for an improved analysis of the balance between fishing capacity and fishing opportunities”, which specify a minimum set of fleet-based technical, biological, economic, and social indicators that purportedly measure the balance between fishing fleets and fish resources. A bioeconomic simulation model was developed to assist in the evaluation of some of these balance indicators. The model is age-structured, like standard single-species stock assessment models, but accommodates multiple independent fish stocks that are harvested by multiple independent fishing fleets. The fish stocks occupy multiple spatial regions with diffusion of fish between regions. The fishing fleets choose where and how to fish based on anticipated profits. Randomness is included in the simulated system in the annual fish recruitments and their spatial distribution. The model was used to generate a series of balance indicators that were then compared against the true conditions in the simulated fisheries to evaluate whether the indicators provide accurate signals of system status. The simulations showed that randomness in recruitment propagates directly into randomness in the balance indicators implying that it will be difficult to detect meaningful signals from any short time series of balance indicator values. Close