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• 1. [Article] The cost of fisheries induced evolution. An example using data for North-East Atlantic cod

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: The cost of fisheries induced evolution. An example using data for North-East Atlantic cod Author: Reithe, Siv Abstract only. Title: The cost of fisheries induced evolution. An example using data for North-East Atlantic cod Author: Reithe, Siv Abstract only. Close

• 2. [Article] Growth Overfishing

  Growth overfishing squanders large parts of the potential rents in fisheries. Many of today’s fisheries are characterized by a severely truncated age-distribution, which in addition may have irreversible ...

  Citation × Citation Citation Abstract Copy Title: Growth Overfishing Author: Diekert, Florian K. Growth overfishing squanders large parts of the potential rents in fisheries. Many of today’s fisheries are characterized by a severely truncated age-distribution, which in addition may have irreversible ecological consequences. Nevertheless, the implications of age-differentiated harvesting for management have received surprisingly little attention in the literature. In the present paper, optimal and non-cooperative exploitation paths for a generic age-distributed resource are derived. We show that, in the case of perfect selectivity, competition between two agents is sufficient to dissipate all rents. Akin to the classical Bertrand competition in prices, each agent has an incentive to target fish at a younger age. That is, the “race to fish” extends to the dimension of age. This observation is crucial also with respect to management: Individual quotas are not able to restore efficiency unless accompanied by gear regulation. Moreover, it turns out that quotas specified in terms of numbers are far superior to those specified in terms of volume or value. Title: Growth Overfishing Author: Diekert, Florian K. Growth overfishing squanders large parts of the potential rents in fisheries. Many of today’s fisheries are characterized by a severely truncated age-distribution, which in addition may have irreversible ecological consequences. Nevertheless, the implications of age-differentiated harvesting for management have received surprisingly little attention in the literature. In the present paper, optimal and non-cooperative exploitation paths for a generic age-distributed resource are derived. We show that, in the case of perfect selectivity, competition between two agents is sufficient to dissipate all rents. Akin to the classical Bertrand competition in prices, each agent has an incentive to target fish at a younger age. That is, the “race to fish” extends to the dimension of age. This observation is crucial also with respect to management: Individual quotas are not able to restore efficiency unless accompanied by gear regulation. Moreover, it turns out that quotas specified in terms of numbers are far superior to those specified in terms of volume or value. Close

• 3. [Article] Fisheries induced evolution. A review

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: Fisheries induced evolution. A review Author: Primicerio, Raul, Reithe, Siv Abstract only. Title: Fisheries induced evolution. A review Author: Primicerio, Raul, Reithe, Siv Abstract only. Close

• 4. [Article] Appreciating the value of age: An evaluation of efficiency gains from controlling gear selectivity under various scenarios

  Abstract only

  Citation × Citation Citation Abstract Copy Title: Appreciating the value of age: An evaluation of efficiency gains from controlling gear selectivity under various scenarios Author: Diekert, Florian Abstract only Title: Appreciating the value of age: An evaluation of efficiency gains from controlling gear selectivity under various scenarios Author: Diekert, Florian Abstract only Close

• 5. [Article] Age-Structured Ecological-Economic Multi-Species Models for Baltic Sea Fisheries

  Abstract Only

  Citation × Citation Citation Abstract Copy Title: Age-Structured Ecological-Economic Multi-Species Models for Baltic Sea Fisheries Author: Quaas, Martin Abstract Only Title: Age-Structured Ecological-Economic Multi-Species Models for Baltic Sea Fisheries Author: Quaas, Martin Abstract Only Close

• 6. [Article] The Spawners' Shadow price: Joint Production of Recruitment and Growth in Agestructured Fish Populations

  Abstract Only

  Citation × Citation Citation Abstract Copy Title: The Spawners' Shadow price: Joint Production of Recruitment and Growth in Agestructured Fish Populations Author: Voss, Rudi, Quaas, Martin Abstract Only Title: The Spawners' Shadow price: Joint Production of Recruitment and Growth in Agestructured Fish Populations Author: Voss, Rudi, Quaas, Martin Abstract Only Close

• 7. [Article] Age, Period, of Birth Cohort: What Determines Demographic Differences in Seafood Consumption?

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Age, Period, of Birth Cohort: What Determines Demographic Differences in Seafood Consumption? Author: Lund, Eiliv, Trondsen, Torbjorn, Scholderer, Joachim Research Paper Title: Age, Period, of Birth Cohort: What Determines Demographic Differences in Seafood Consumption? Author: Lund, Eiliv, Trondsen, Torbjorn, Scholderer, Joachim Research Paper Close

• 8. [Article] Optimal Management of the Baltic Sea Fishery Under Climate Change: An Ecological-Economic Age-Structured Multi-Species Model Analysis

  Abstract only.

  Citation × Citation Citation Abstract Copy Title: Optimal Management of the Baltic Sea Fishery Under Climate Change: An Ecological-Economic Age-Structured Multi-Species Model Analysis Author: Voss, Rüdiger, Neuenfeldt, Stefan, Quaas, Martin F., Schmidt, Jörn O. Abstract only. Title: Optimal Management of the Baltic Sea Fishery Under Climate Change: An Ecological-Economic Age-Structured Multi-Species Model Analysis Author: Voss, Rüdiger, Neuenfeldt, Stefan, Quaas, Martin F., Schmidt, Jörn O. Abstract only. Close

• 9. [Article] Determining Optimal Catch in Age-Structural Multispecies Fisheries

  This study investigates optimal catch of Barents Sea stocks, namely Northeast Arctic Cod and Capelin in multispecies ecosystem. We solve a multispecies age structured bioeconomic model for predator-prey ...

  Citation × Citation Citation Abstract Copy Title: Determining Optimal Catch in Age-Structural Multispecies Fisheries Author: Steinshamn, Stein Ivar, Poudel, Diwakar This study investigates optimal catch of Barents Sea stocks, namely Northeast Arctic Cod and Capelin in multispecies ecosystem. We solve a multispecies age structured bioeconomic model for predator-prey interaction. Barents Sea stock data from ICES are employed for model application. Among others, we also include sustainability constraint in the model that contributes towards ecosystem based management of fishery. Our preliminary result suggests that a conservative harvest is optimal for capelin compared to the single species model and a higher harvest is possible in cod in multispecies model. Furthermore, we found that a pulse fishing yields higher value in cod (predator) compared to the uniform (current) fishing policy. Title: Determining Optimal Catch in Age-Structural Multispecies Fisheries Author: Steinshamn, Stein Ivar, Poudel, Diwakar This study investigates optimal catch of Barents Sea stocks, namely Northeast Arctic Cod and Capelin in multispecies ecosystem. We solve a multispecies age structured bioeconomic model for predator-prey interaction. Barents Sea stock data from ICES are employed for model application. Among others, we also include sustainability constraint in the model that contributes towards ecosystem based management of fishery. Our preliminary result suggests that a conservative harvest is optimal for capelin compared to the single species model and a higher harvest is possible in cod in multispecies model. Furthermore, we found that a pulse fishing yields higher value in cod (predator) compared to the uniform (current) fishing policy. Close

• 10. [Article] Contribution of Children in Artisanal Fisheries to Households’ Poverty Alleviation in Ondo State, Nigeria

  Despite the global clamour for the eradication of child labour in agriculture, children in developing countries continue to be prominent actors in the fisheries sector though their contribution is unrecorded ...

  Citation × Citation Citation Abstract Copy Title: Contribution of Children in Artisanal Fisheries to Households’ Poverty Alleviation in Ondo State, Nigeria Author: Mafimisebi, Taiwo Ejiola, Fasina, Oluwatosin Despite the global clamour for the eradication of child labour in agriculture, children in developing countries continue to be prominent actors in the fisheries sector though their contribution is unrecorded in the national income accounts of many countries. The study examined the involvement of children in artisanal fisheries in Ondo State, Nigeria. Simple random sampling procedure was used to select 90 children aged 9-18 years who were involved in artisanal fishing activities. Descriptive statistics were used to present the data gathered for the study. Pearson Product Moment Correlation and the Chi-Square analysis were used to test the study hypotheses at the 0.05 level of significance. Respondents were mostly males (70%) with mean age of 15 ± 2 years. Fishing experience for two-thirds was over 7 years. Major economic activities engaged in by children were fishing (100.0%) and fish marketing (97.8%). All respondents fished more on rivers, lakes, creeks and canals with friends mostly in the mornings (70.0%) between 4-5am (43.3%). Mean daily catch per caput per day amounted in monetary terms to N317. Income increased significantly with age of children (r = 0.27, p< 0.05). Respondents’ major constraint was lack of capital to purchase nets and boats of their own (97.8%). Sustainable involvement of children in artisanal fisheries can help alleviate poverty as the children remitted their incomes to their parents for food, school fees or other school needs. Children’s capacity for production can be boosted through capacity building and greater access to fishing equipment and capital assets used in fishing. Scholarship programmes should be put in place to encourage children who do well at both school and fishing to further develop the quality of future manpower available for fishing in the coastal areas. Title: Contribution of Children in Artisanal Fisheries to Households’ Poverty Alleviation in Ondo State, Nigeria Author: Mafimisebi, Taiwo Ejiola, Fasina, Oluwatosin Despite the global clamour for the eradication of child labour in agriculture, children in developing countries continue to be prominent actors in the fisheries sector though their contribution is unrecorded in the national income accounts of many countries. The study examined the involvement of children in artisanal fisheries in Ondo State, Nigeria. Simple random sampling procedure was used to select 90 children aged 9-18 years who were involved in artisanal fishing activities. Descriptive statistics were used to present the data gathered for the study. Pearson Product Moment Correlation and the Chi-Square analysis were used to test the study hypotheses at the 0.05 level of significance. Respondents were mostly males (70%) with mean age of 15 ± 2 years. Fishing experience for two-thirds was over 7 years. Major economic activities engaged in by children were fishing (100.0%) and fish marketing (97.8%). All respondents fished more on rivers, lakes, creeks and canals with friends mostly in the mornings (70.0%) between 4-5am (43.3%). Mean daily catch per caput per day amounted in monetary terms to N317. Income increased significantly with age of children (r = 0.27, p< 0.05). Respondents’ major constraint was lack of capital to purchase nets and boats of their own (97.8%). Sustainable involvement of children in artisanal fisheries can help alleviate poverty as the children remitted their incomes to their parents for food, school fees or other school needs. Children’s capacity for production can be boosted through capacity building and greater access to fishing equipment and capital assets used in fishing. Scholarship programmes should be put in place to encourage children who do well at both school and fishing to further develop the quality of future manpower available for fishing in the coastal areas. Close

• 11. [Article] Participation in Vessel Buyback Programs: An Option Value Model of the Vessel-Scrapping Decision

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Participation in Vessel Buyback Programs: An Option Value Model of the Vessel-Scrapping Decision Author: Chen, Chin-Chen, Lee, Yao-Hsien, Ching-Ta, Chung Research Paper Title: Participation in Vessel Buyback Programs: An Option Value Model of the Vessel-Scrapping Decision Author: Chen, Chin-Chen, Lee, Yao-Hsien, Ching-Ta, Chung Research Paper Close

• 12. [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

• 13. [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

• 14. [Article] Viability of Transboundary Fisheries and International Quota Sharing

  This paper examines the viability of the management of a transboundary resource, the Bay of Biscay anchovy (Engraulis encrasicolus L.). A deterministic model is used to simulate the anchovy dynamics, with ...

  Citation × Citation Citation Abstract Copy Title: Viability of Transboundary Fisheries and International Quota Sharing Author: Curtin, Richard, Martinet, Vincent This paper examines the viability of the management of a transboundary resource, the Bay of Biscay anchovy (Engraulis encrasicolus L.). A deterministic model is used to simulate the anchovy dynamics, with the fish stock consisting of two age groups, “young" and “old", while recruitment follows a Beverton Holt pattern. Two countries, France and Spain, harvest the resource, with two different types of gear, the purse seiner for Spain and the pelagic trawler for France. These technologies impact the different age-groups of anchovy at differing rates. A regulatory agency defines an annual fishing quota and its allocation between the two countries, with the aim of sustainability in the overall allocation design. A set of constraints is defined to describe the sustainability of the system which encompasses the economic, ecological and social aspects of the fishery. The optimal harvest share between the two countries is found and a number of scenarios are then tested in relation to their ability to remain within the set of constraints, or viability kernel. Other scenarios, including the historical trajectory, the optimal harvest share trajectory and the minimum time of crisis trajectory, are examined. Title: Viability of Transboundary Fisheries and International Quota Sharing Author: Curtin, Richard, Martinet, Vincent This paper examines the viability of the management of a transboundary resource, the Bay of Biscay anchovy (Engraulis encrasicolus L.). A deterministic model is used to simulate the anchovy dynamics, with the fish stock consisting of two age groups, “young" and “old", while recruitment follows a Beverton Holt pattern. Two countries, France and Spain, harvest the resource, with two different types of gear, the purse seiner for Spain and the pelagic trawler for France. These technologies impact the different age-groups of anchovy at differing rates. A regulatory agency defines an annual fishing quota and its allocation between the two countries, with the aim of sustainability in the overall allocation design. A set of constraints is defined to describe the sustainability of the system which encompasses the economic, ecological and social aspects of the fishery. The optimal harvest share between the two countries is found and a number of scenarios are then tested in relation to their ability to remain within the set of constraints, or viability kernel. Other scenarios, including the historical trajectory, the optimal harvest share trajectory and the minimum time of crisis trajectory, are examined. Close

• 15. [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

• 16. [Article] From Shark Fin Markets to Shark Populations: An Integrated Market Preference Cohort Analysis Of the Blacktip Shark (Carcharhinus limbatus)

  The increasing demand for shark fins in Asia and the shark s life history pattern of slow growth, late maturity, and few offspring, have generated concerns regarding the sustainability of shark resources. ...

  Citation × Citation Citation Abstract Copy Title: From Shark Fin Markets to Shark Populations: An Integrated Market Preference Cohort Analysis Of the Blacktip Shark (Carcharhinus limbatus) Author: Fong, Quentin S.W., Anderson, James L. Year: 2001 The increasing demand for shark fins in Asia and the shark s life history pattern of slow growth, late maturity, and few offspring, have generated concerns regarding the sustainability of shark resources. Despite this concern, little effort has been spent on understanding the markets for shark fin products and the population dynamics of sharks. This work incorporates the results of a conjoint analysis of dried processed shark fins from Hong Kong into a cohort model of the balcktip shark with the objective of maximizing the utility of Hong Kong shark fin importers/processors. Results show that optimal harvest sizes and ages for all mortality and discount factor scenarios are greater than the maturation sizes and ages for both male and female blacktip. Policy implications for this study are also discussed. Title: From Shark Fin Markets to Shark Populations: An Integrated Market Preference Cohort Analysis Of the Blacktip Shark (Carcharhinus limbatus) Author: Fong, Quentin S.W., Anderson, James L. Year: 2001 The increasing demand for shark fins in Asia and the shark s life history pattern of slow growth, late maturity, and few offspring, have generated concerns regarding the sustainability of shark resources. Despite this concern, little effort has been spent on understanding the markets for shark fin products and the population dynamics of sharks. This work incorporates the results of a conjoint analysis of dried processed shark fins from Hong Kong into a cohort model of the balcktip shark with the objective of maximizing the utility of Hong Kong shark fin importers/processors. Results show that optimal harvest sizes and ages for all mortality and discount factor scenarios are greater than the maturation sizes and ages for both male and female blacktip. Policy implications for this study are also discussed. Close

• 17. [Article] The Stability of Rent Maximization in the Western and Central Pacific Fishery

  The potential for achieving sustainable and efficient harvesting of three species of migratory tuna in the Western and Central Pacific Ocean is examined. The stocks reside in exclusive economic zones (mainly ...

  Citation × Citation Citation Abstract Copy Title: The Stability of Rent Maximization in the Western and Central Pacific Fishery Author: Kennedy, John, Hannesson, Rögnvaldur The potential for achieving sustainable and efficient harvesting of three species of migratory tuna in the Western and Central Pacific Ocean is examined. The stocks reside in exclusive economic zones (mainly those of Pacific island countries) and in the high seas. Most harvesting is carried out by distant water fishing nations, including the USA, Japan, Taiwan, China and Korea. Problems of achieving sustainability and efficiency in the harvesting of the stocks by disparate countries are made more difficult due to changes in the harvesting levels of one fleet affecting the rents of another fleet through changes in the age distribution of stock. These types of problem are under review by the Western and Central Pacific Fisheries Commission. Results from an age-structured steady-state bioeconomic model are used to show: the changes in fleet rents and catches of tuna if all fleets form a cooperative grand coalition to deploy fishing effort to maximize rents over the region; the likely non-stability of the grand coalition; and the inferior Nash Equilibria outcomes if fleets fish non-cooperatively to maximize their own rents. Title: The Stability of Rent Maximization in the Western and Central Pacific Fishery Author: Kennedy, John, Hannesson, Rögnvaldur The potential for achieving sustainable and efficient harvesting of three species of migratory tuna in the Western and Central Pacific Ocean is examined. The stocks reside in exclusive economic zones (mainly those of Pacific island countries) and in the high seas. Most harvesting is carried out by distant water fishing nations, including the USA, Japan, Taiwan, China and Korea. Problems of achieving sustainability and efficiency in the harvesting of the stocks by disparate countries are made more difficult due to changes in the harvesting levels of one fleet affecting the rents of another fleet through changes in the age distribution of stock. These types of problem are under review by the Western and Central Pacific Fisheries Commission. Results from an age-structured steady-state bioeconomic model are used to show: the changes in fleet rents and catches of tuna if all fleets form a cooperative grand coalition to deploy fishing effort to maximize rents over the region; the likely non-stability of the grand coalition; and the inferior Nash Equilibria outcomes if fleets fish non-cooperatively to maximize their own rents. Close

• 18. [Article] Optimal Harvest in a Multispecies Age Structured Fishery Model at Different Level of Density Dependency

  Presentation

  Citation × Citation Citation Abstract Copy Title: Optimal Harvest in a Multispecies Age Structured Fishery Model at Different Level of Density Dependency Author: Poudel, Diwakar Presentation Title: Optimal Harvest in a Multispecies Age Structured Fishery Model at Different Level of Density Dependency Author: Poudel, Diwakar Presentation Close

• 19. [Article] Economics of Fish Harvesting in Nigeria: A Case Study of Yola North Local Government Area of Adamawa State

  Powerpoint Presentation and Research Paper

  Citation × Citation Citation Abstract Copy Title: Economics of Fish Harvesting in Nigeria: A Case Study of Yola North Local Government Area of Adamawa State Author: Adebayo, Elizabeth Powerpoint Presentation and Research Paper Title: Economics of Fish Harvesting in Nigeria: A Case Study of Yola North Local Government Area of Adamawa State Author: Adebayo, Elizabeth Powerpoint Presentation and Research Paper Close

• 20. [Article] Misplaced Concreteness: Prospects and Problems with Interdisciplinary Approaches to the Fisheries

  In an age of increasing complexity, simple answers no longer suffice, but the demand for greater sophistication is itself at odds with an era of growing specialization. Researchers must thus incorporate ...

  Citation × Citation Citation Abstract Copy Title: Misplaced Concreteness: Prospects and Problems with Interdisciplinary Approaches to the Fisheries Author: Tayloe, Joseph E. III Year: 2001 In an age of increasing complexity, simple answers no longer suffice, but the demand for greater sophistication is itself at odds with an era of growing specialization. Researchers must thus incorporate information from specialists in other fields. This trend in interdisciplinary research contains hidden challenges, however, including a necessary familiarity with the development, ideas, major questions, and dominant institutions of those disciplines. Title: Misplaced Concreteness: Prospects and Problems with Interdisciplinary Approaches to the Fisheries Author: Tayloe, Joseph E. III Year: 2001 In an age of increasing complexity, simple answers no longer suffice, but the demand for greater sophistication is itself at odds with an era of growing specialization. Researchers must thus incorporate information from specialists in other fields. This trend in interdisciplinary research contains hidden challenges, however, including a necessary familiarity with the development, ideas, major questions, and dominant institutions of those disciplines. Close