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• 1. [Article] Spatial Integration of Freshwater Fish Markets in the Northern Baltic Sea Area

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Spatial Integration of Freshwater Fish Markets in the Northern Baltic Sea Area Author: Honkanen, Asmo, Nielsen, Max, Virtanen, Jarno, Setala, Jari, Laitinen, Jukka, Saarni, Kaija Research Paper Title: Spatial Integration of Freshwater Fish Markets in the Northern Baltic Sea Area Author: Honkanen, Asmo, Nielsen, Max, Virtanen, Jarno, Setala, Jari, Laitinen, Jukka, Saarni, Kaija Research Paper Close

• 2. [Article] Indicators for Ecosystem Externalities in Fishing

  Ecosystem externalities arise when one use of an ecosystem affects its other uses through the production functions of the ecosystem. We use simulations from a size-spectrum ecosystem model to investigate ...

  Citation × Citation Citation Abstract Copy Title: Indicators for Ecosystem Externalities in Fishing Author: Andersen, Ken H., Vestergaard, Niels, Ravn-Jonsen, Lars Ecosystem externalities arise when one use of an ecosystem affects its other uses through the production functions of the ecosystem. We use simulations from a size-spectrum ecosystem model to investigate the ecosystem externality created by fishing of multiple species. The model is based upon general ecological principles and is calibrated to the North Sea. Two fleets are considered: a `forage fish’ fleet targeting species that mature at small sizes and a `large fish’ fleet targeting large piscivorous species. Based on the marginal analysis of the present value of the rent, we develop a benefit indicator that explicitly divides the consequences of fishing into internal and external benefits. This analysis demonstrates that the forage fish fleet has a notable economic impact on the large fish fleet, but the reverse is not true. The impact can be either negative or positive, which entails that for optimal economic exploitation, the forage fishery has to be adjusted according to the large fish fishery. With the present large fish fishery in the North Sea, the two fisheries are well adjusted; however, the present combined exploration level is too high to achieve optimal economic rents. Title: Indicators for Ecosystem Externalities in Fishing Author: Andersen, Ken H., Vestergaard, Niels, Ravn-Jonsen, Lars Ecosystem externalities arise when one use of an ecosystem affects its other uses through the production functions of the ecosystem. We use simulations from a size-spectrum ecosystem model to investigate the ecosystem externality created by fishing of multiple species. The model is based upon general ecological principles and is calibrated to the North Sea. Two fleets are considered: a `forage fish’ fleet targeting species that mature at small sizes and a `large fish’ fleet targeting large piscivorous species. Based on the marginal analysis of the present value of the rent, we develop a benefit indicator that explicitly divides the consequences of fishing into internal and external benefits. This analysis demonstrates that the forage fish fleet has a notable economic impact on the large fish fleet, but the reverse is not true. The impact can be either negative or positive, which entails that for optimal economic exploitation, the forage fishery has to be adjusted according to the large fish fishery. With the present large fish fishery in the North Sea, the two fisheries are well adjusted; however, the present combined exploration level is too high to achieve optimal economic rents. Close

• 3. [Article] Price and Quantity Indices for Aquaculture Production in Europe

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Price and Quantity Indices for Aquaculture Production in Europe Author: Millán, Joaquín A., Aldaz, Natalia Research Paper Title: Price and Quantity Indices for Aquaculture Production in Europe Author: Millán, Joaquín A., Aldaz, Natalia Research Paper Close

• 4. [Article] Evaluating the Accuracy of Trawl Logbook Estimates of Groundfish Discards

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Evaluating the Accuracy of Trawl Logbook Estimates of Groundfish Discards Author: Sampson, David B., Lee, Yong-Woo Research Paper Title: Evaluating the Accuracy of Trawl Logbook Estimates of Groundfish Discards Author: Sampson, David B., Lee, Yong-Woo Research Paper Close

• 5. [Article] Causality and Price Transmission Between Fish Prices: New Evidence from Greece and UK

  This paper re-examines the evidence of causality and price transmission between fish prices of main species landed into Piraeus (Greece) and Cornwall (UK). To complete the analysis of cointegration and ...

  Citation × Citation Citation Abstract Copy Title: Causality and Price Transmission Between Fish Prices: New Evidence from Greece and UK Author: Floros, Christos This paper re-examines the evidence of causality and price transmission between fish prices of main species landed into Piraeus (Greece) and Cornwall (UK). To complete the analysis of cointegration and causality, we use the data of Floros and Failler (2004) and Avdelas (2004). Our paper uses the Bivariate Generalised Autoregressive Conditional Heteroscedastic (BGARCH) model. The Bivariate cointegration model (with GARCH error structure) incorporates a time varying conditional correlation coefficient between fish prices and generates time-varying covariances. The results from BGARCH show evidence of volatility clustering in the change of fish prices, and report that most species lead Hake (this is stronger for Greece). Furthermore, the estimates of price transmission indicate that the rate of change of Shrimp/Dentex partially adjusts to the rate of change of Hake prices. Our results suggest significant imperfect price transmission between species (this is stronger for Greece). Title: Causality and Price Transmission Between Fish Prices: New Evidence from Greece and UK Author: Floros, Christos This paper re-examines the evidence of causality and price transmission between fish prices of main species landed into Piraeus (Greece) and Cornwall (UK). To complete the analysis of cointegration and causality, we use the data of Floros and Failler (2004) and Avdelas (2004). Our paper uses the Bivariate Generalised Autoregressive Conditional Heteroscedastic (BGARCH) model. The Bivariate cointegration model (with GARCH error structure) incorporates a time varying conditional correlation coefficient between fish prices and generates time-varying covariances. The results from BGARCH show evidence of volatility clustering in the change of fish prices, and report that most species lead Hake (this is stronger for Greece). Furthermore, the estimates of price transmission indicate that the rate of change of Shrimp/Dentex partially adjusts to the rate of change of Hake prices. Our results suggest significant imperfect price transmission between species (this is stronger for Greece). Close

• 6. [Article] Eco-labeled Marine Ornamentals: Expected Demand and Value from a Conjoint Survey

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Eco-labeled Marine Ornamentals: Expected Demand and Value from a Conjoint Survey Author: Degner, Robert, Larkin, Sherry Research Paper Title: Eco-labeled Marine Ornamentals: Expected Demand and Value from a Conjoint Survey Author: Degner, Robert, Larkin, Sherry Research Paper Close

• 7. [Article] Estimating Heterogeneous Primal Capacity and Capacity Utilization Measures in a Multi-Species Fishery

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Estimating Heterogeneous Primal Capacity and Capacity Utilization Measures in a Multi-Species Fishery Author: Felthoven, Ronald, Schnier, Kurt Research Paper Title: Estimating Heterogeneous Primal Capacity and Capacity Utilization Measures in a Multi-Species Fishery Author: Felthoven, Ronald, Schnier, Kurt Research Paper Close

• 8. [Article] Testing the Cost Effectiveness of Manual Removal Strategies for the Containment of Invasive Lionfish Stocks in a Caribbean Reef

  Two species of the Indo-Pacific lionfish (Pterois miles and P. volitans) have rapidly expanded throughout the Gulf of Mexico, mid- and south Atlantic and the Caribbean following their introduction to Florida ...

  Citation × Citation Citation Abstract Copy Title: Testing the Cost Effectiveness of Manual Removal Strategies for the Containment of Invasive Lionfish Stocks in a Caribbean Reef Author: Valderrama, Diego, Fields, Kathryn Ann H. Two species of the Indo-Pacific lionfish (Pterois miles and P. volitans) have rapidly expanded throughout the Gulf of Mexico, mid- and south Atlantic and the Caribbean following their introduction to Florida coastal waters during the mid-1980s through releases from marine aquaria. There is overwhelming scientific agreement on the threats that this invasion poses to a wide range of native species, including grunts, snappers, and groupers. Because eradication of lionfish is unfeasible, scientists and conservationists are urging the implementation of lionfish management plans in order to reduce the environmental and economic impacts of the invasion to a manageable scale. Recent studies indicate that persistent removal of lionfish by spearheading does help control lionfish populations and help native fishing rebound. Through mathematical modeling and field tests, researchers have found that reducing lionfish stocks by about 75 to 90 percent leads to the rapid recovery of native fish numbers (Green et al. 2014). Data on prey fish and lionfish densities as well as spearheading catch rates were collected from lionfish derbies held at the Bacalar Chico Marine Reserve, Belize, in 2014. These data were used to estimate reef-specific target lionfish densities leading to the recovery of native prey species in the marine reserve as predicted by the Green et al. (2014) model. The fishing costs involved in reaching the target densities were also estimated to evaluate the overall effectiveness of manual removal techniques as a management strategy for invasive lionfish stocks. Title: Testing the Cost Effectiveness of Manual Removal Strategies for the Containment of Invasive Lionfish Stocks in a Caribbean Reef Author: Valderrama, Diego, Fields, Kathryn Ann H. Two species of the Indo-Pacific lionfish (Pterois miles and P. volitans) have rapidly expanded throughout the Gulf of Mexico, mid- and south Atlantic and the Caribbean following their introduction to Florida coastal waters during the mid-1980s through releases from marine aquaria. There is overwhelming scientific agreement on the threats that this invasion poses to a wide range of native species, including grunts, snappers, and groupers. Because eradication of lionfish is unfeasible, scientists and conservationists are urging the implementation of lionfish management plans in order to reduce the environmental and economic impacts of the invasion to a manageable scale. Recent studies indicate that persistent removal of lionfish by spearheading does help control lionfish populations and help native fishing rebound. Through mathematical modeling and field tests, researchers have found that reducing lionfish stocks by about 75 to 90 percent leads to the rapid recovery of native fish numbers (Green et al. 2014). Data on prey fish and lionfish densities as well as spearheading catch rates were collected from lionfish derbies held at the Bacalar Chico Marine Reserve, Belize, in 2014. These data were used to estimate reef-specific target lionfish densities leading to the recovery of native prey species in the marine reserve as predicted by the Green et al. (2014) model. The fishing costs involved in reaching the target densities were also estimated to evaluate the overall effectiveness of manual removal techniques as a management strategy for invasive lionfish stocks. Close

• 9. [Article] Global Ex-Vessel Fish Price Database: Construction and Applications

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Global Ex-Vessel Fish Price Database: Construction and Applications Author: Sumaila, Ussif Rashid, Pauly, Daniel, Marsden, A. Dale, Watson, Reg Research Paper Title: Global Ex-Vessel Fish Price Database: Construction and Applications Author: Sumaila, Ussif Rashid, Pauly, Daniel, Marsden, A. Dale, Watson, Reg Research Paper Close

• 10. [Article] A Bioeconomic Simulation Model of a Fishery Using Area Rotation Under Uncertainty

  Research Paper

  Citation × Citation Citation Abstract Copy Title: A Bioeconomic Simulation Model of a Fishery Using Area Rotation Under Uncertainty Author: Quigley-Lemieux, Kathryn, Sylvia, Gil Research Paper Title: A Bioeconomic Simulation Model of a Fishery Using Area Rotation Under Uncertainty Author: Quigley-Lemieux, Kathryn, Sylvia, Gil Research Paper Close

• 11. [Article] Presentation of the newly launched INCOFISH portal at www.incofish.org

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Presentation of the newly launched INCOFISH portal at www.incofish.org Author: Opitz, Silvia Research Paper Title: Presentation of the newly launched INCOFISH portal at www.incofish.org Author: Opitz, Silvia Research Paper Close

• 12. [Article] Measuring Economic Performance in a Fishery: An Index Number Profit Decomposition

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Measuring Economic Performance in a Fishery: An Index Number Profit Decomposition Author: Nhu Che, Tuong, Grafton, R. Quentin, Kompas, Tom, Fox, Kevin J. Research Paper Title: Measuring Economic Performance in a Fishery: An Index Number Profit Decomposition Author: Nhu Che, Tuong, Grafton, R. Quentin, Kompas, Tom, Fox, Kevin J. Research Paper Close

• 13. [Article] Trade Restrictions and the Development of Salmon Production

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Trade Restrictions and the Development of Salmon Production Author: Asche, Frank Research Paper Title: Trade Restrictions and the Development of Salmon Production Author: Asche, Frank Research Paper Close

• 14. [Article] The Cost of Avoiding Sea Cucumber Stock Depletion

  In 2013 a stock of sea cucumber (Isostichopus badionotus) was discovered in northern shelf of Yucatan. A survey calculated a biomass of 17,600 tons. The species has an attractive price for local fishers, ...

  Citation × Citation Citation Abstract Copy Title: The Cost of Avoiding Sea Cucumber Stock Depletion Author: Hernández-Flores, Alvaro, Cuevas-Jiménez, Alfonso, Aranda-Nah, Javier In 2013 a stock of sea cucumber (Isostichopus badionotus) was discovered in northern shelf of Yucatan. A survey calculated a biomass of 17,600 tons. The species has an attractive price for local fishers, therefore, in order to avoid the “race for sea cucumbers” and the collapse of the stock, authorities established a total quota of 1,278 tones, issued a limited number of permits and restricted the fishing season to six weeks. Because of fishers’ dynamic behavior and the installed local fishing capacity, the applied effort was higher than the authorized (750 boats per day). Regulations were not enough to avoid excess fishing and entry of non-authorized boats, driving the stock to a low level. We developed a spatial and density dependent bioeconomic model which calculates an optimum pathway to maximize the profits without putting the stock in peril. The model operates seasonally in the short-run. Because of catchability and cost depend on the sea cucumbers densities, both were modeled with asymptotic functions. In order to avoid the Allee effect, the species requires a minimum density of 0.1 individuals per square meter. Our results indicate that the maximum quota could be 5,700 tons, which is about 32% of the vulnerable biomass. This quota would produce profits of US$2,300,000. If minimum density were neglected, the system would lead the biomass to 8,400 tons, instead 11,000 tons, with extra profits of US$76,000; however, in such level the density would be 0.08 individual per square meter, reaching the Allee effect and impeding the stock recovery. Title: The Cost of Avoiding Sea Cucumber Stock Depletion Author: Hernández-Flores, Alvaro, Cuevas-Jiménez, Alfonso, Aranda-Nah, Javier In 2013 a stock of sea cucumber (Isostichopus badionotus) was discovered in northern shelf of Yucatan. A survey calculated a biomass of 17,600 tons. The species has an attractive price for local fishers, therefore, in order to avoid the “race for sea cucumbers” and the collapse of the stock, authorities established a total quota of 1,278 tones, issued a limited number of permits and restricted the fishing season to six weeks. Because of fishers’ dynamic behavior and the installed local fishing capacity, the applied effort was higher than the authorized (750 boats per day). Regulations were not enough to avoid excess fishing and entry of non-authorized boats, driving the stock to a low level. We developed a spatial and density dependent bioeconomic model which calculates an optimum pathway to maximize the profits without putting the stock in peril. The model operates seasonally in the short-run. Because of catchability and cost depend on the sea cucumbers densities, both were modeled with asymptotic functions. In order to avoid the Allee effect, the species requires a minimum density of 0.1 individuals per square meter. Our results indicate that the maximum quota could be 5,700 tons, which is about 32% of the vulnerable biomass. This quota would produce profits of US$2,300,000. If minimum density were neglected, the system would lead the biomass to 8,400 tons, instead 11,000 tons, with extra profits of US$76,000; however, in such level the density would be 0.08 individual per square meter, reaching the Allee effect and impeding the stock recovery. Close

• 15. [Article] Fish consumption within the Finnish catering market

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Fish consumption within the Finnish catering market Author: Honkanen, Asmo Research Paper Title: Fish consumption within the Finnish catering market Author: Honkanen, Asmo Research Paper Close

• 16. [Article] Comprehensive Fishery Wealth: A Bioeconomic, Ecosystem-Based Approach to Measuring Fisheries Sustainability

  Fisheries sustainability is a much sought-after goal. Yet, “sustainability” is often too ambiguously defined to be of much practical guidance to policymakers. Furthermore, fisheries managers are increasingly ...

  Citation × Citation Citation Abstract Copy Title: Comprehensive Fishery Wealth: A Bioeconomic, Ecosystem-Based Approach to Measuring Fisheries Sustainability Author: Fenichel, Eli P., Abbott, Joshua K. Fisheries sustainability is a much sought-after goal. Yet, “sustainability” is often too ambiguously defined to be of much practical guidance to policymakers. Furthermore, fisheries managers are increasingly expected to assess and manage fisheries in an “ecosystem-based” manner – accounting for the ecological interdependencies of species and their coupling with the physical environment. We build upon the green accounting and sustainable development literatures to downscale indices often used to measure sustainability at the nation-state scale to measure the current and projected future sustainability of exploited fishery ecosystems. We argue that the sustainability of a fishery ecosystem can be assessed by whether the properly measured value of the natural, physical and human capital stocks embodied within the fishery (i.e., the comprehensive fishery wealth) is non-decreasing over time. We extend our published work (Fenichel and Abbott 2014) to show how ecosystem models of fisheries can be integrated with bioeconomic models of human “predators’” responses to changes in multispecies fish stocks and policy to provide rigorous “shadow prices” for all species within the system and fishing capital. These prices can then be multiplied by their associated capital stocks to provide an index of inclusive fishery wealth. Changes in this index (i.e., comprehensive investment) allow managers to assess the ability of past and current fishery management regimes to maintain wealth within the fishery for future generations. Finally, we show how our wealth accounting approach – when coupled with ecosystem-based bioeconomic models – can be leveraged to prospectively evaluate the sustainability and efficiency of alternative management approaches. Title: Comprehensive Fishery Wealth: A Bioeconomic, Ecosystem-Based Approach to Measuring Fisheries Sustainability Author: Fenichel, Eli P., Abbott, Joshua K. Fisheries sustainability is a much sought-after goal. Yet, “sustainability” is often too ambiguously defined to be of much practical guidance to policymakers. Furthermore, fisheries managers are increasingly expected to assess and manage fisheries in an “ecosystem-based” manner – accounting for the ecological interdependencies of species and their coupling with the physical environment. We build upon the green accounting and sustainable development literatures to downscale indices often used to measure sustainability at the nation-state scale to measure the current and projected future sustainability of exploited fishery ecosystems. We argue that the sustainability of a fishery ecosystem can be assessed by whether the properly measured value of the natural, physical and human capital stocks embodied within the fishery (i.e., the comprehensive fishery wealth) is non-decreasing over time. We extend our published work (Fenichel and Abbott 2014) to show how ecosystem models of fisheries can be integrated with bioeconomic models of human “predators’” responses to changes in multispecies fish stocks and policy to provide rigorous “shadow prices” for all species within the system and fishing capital. These prices can then be multiplied by their associated capital stocks to provide an index of inclusive fishery wealth. Changes in this index (i.e., comprehensive investment) allow managers to assess the ability of past and current fishery management regimes to maintain wealth within the fishery for future generations. Finally, we show how our wealth accounting approach – when coupled with ecosystem-based bioeconomic models – can be leveraged to prospectively evaluate the sustainability and efficiency of alternative management approaches. Close

• 17. [Article] The Effects of Derelict Gear on Blue Crab Production in the Chesapeake Bay

  Several factors currently threaten blue crab (Callinectes sapidus) in the Chesapeake Bay. In addition to poor water quality, degraded habitat, and shifting environmental conditions, derelict gear has recently ...

  Citation × Citation Citation Abstract Copy Title: The Effects of Derelict Gear on Blue Crab Production in the Chesapeake Bay Author: Bilkovic, Donna M., Scheld, Andrew M., Havens, Kirk J. Several factors currently threaten blue crab (Callinectes sapidus) in the Chesapeake Bay. In addition to poor water quality, degraded habitat, and shifting environmental conditions, derelict gear has recently been recognized as a significant source of mortality for this economically and culturally significant species. From 2008 through 2014, commercial watermen in Virginia were hired during their winter off season to locate, document, and remove derelict gear as part of a larger research effort to determine the biological impacts of marine debris in the Chesapeake Bay. Data on derelict gear removal generated by this research was subsequently paired with spatially resolved catch and effort data and entered into a translog production model used to estimate the economic effects of derelict gear on commercial blue crab production. Model results indicate removal significantly improved pot production and economic profits, a finding which had been previously confounded by concurrent blue crab management action. Our research builds on previous work through explicit acknowledgment of important spatial production differences and incorporation of derelict gear removal. Title: The Effects of Derelict Gear on Blue Crab Production in the Chesapeake Bay Author: Bilkovic, Donna M., Scheld, Andrew M., Havens, Kirk J. Several factors currently threaten blue crab (Callinectes sapidus) in the Chesapeake Bay. In addition to poor water quality, degraded habitat, and shifting environmental conditions, derelict gear has recently been recognized as a significant source of mortality for this economically and culturally significant species. From 2008 through 2014, commercial watermen in Virginia were hired during their winter off season to locate, document, and remove derelict gear as part of a larger research effort to determine the biological impacts of marine debris in the Chesapeake Bay. Data on derelict gear removal generated by this research was subsequently paired with spatially resolved catch and effort data and entered into a translog production model used to estimate the economic effects of derelict gear on commercial blue crab production. Model results indicate removal significantly improved pot production and economic profits, a finding which had been previously confounded by concurrent blue crab management action. Our research builds on previous work through explicit acknowledgment of important spatial production differences and incorporation of derelict gear removal. Close

• 18. [Article] Measuring Productivity Change and its Components for Fisheries: The Alaskan Pollock Fishery, 1994-2003

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Measuring Productivity Change and its Components for Fisheries: The Alaskan Pollock Fishery, 1994-2003 Author: Morrison-Paul, Catherine, Torres, Marcelo Research Paper Title: Measuring Productivity Change and its Components for Fisheries: The Alaskan Pollock Fishery, 1994-2003 Author: Morrison-Paul, Catherine, Torres, Marcelo Research Paper Close

• 19. [Article] Bioeconomic Analysis of the Artisanal Shrimp Trawl Fishery in the Tonkin Gulf, Vietnam

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Bioeconomic Analysis of the Artisanal Shrimp Trawl Fishery in the Tonkin Gulf, Vietnam Author: Eide, Arne, Thanh, Nguyen Viet Research Paper Title: Bioeconomic Analysis of the Artisanal Shrimp Trawl Fishery in the Tonkin Gulf, Vietnam Author: Eide, Arne, Thanh, Nguyen Viet Research Paper Close

• 20. [Article] Sustainable Management of the Shrimp Trawl Fishery in Tonkin Gulf, Vietnam

  This study investigates the sustainability of shrimp stock in the trawl fishery in the Tonkin Gulf, Vietnam. It is a small scale and multi species fishery. The Verhulst-Schaefer and Gompertz-Fox surplus ...

  Citation × Citation Citation Abstract Copy Title: Sustainable Management of the Shrimp Trawl Fishery in Tonkin Gulf, Vietnam Author: Nguyen, Viet Thanh This study investigates the sustainability of shrimp stock in the trawl fishery in the Tonkin Gulf, Vietnam. It is a small scale and multi species fishery. The Verhulst-Schaefer and Gompertz-Fox surplus production models are applied. There are two shrimp spawning seasons in a year in the Gulf. Therefore, in this study, the surplus production models, associated to catch calendar and effort data, are applied for a half-year time interval. The results indicate that the fishing effort should be reduced by roughly 12-44% to achieve the maximum sustainable yield and 46-61% to reach the maximum economic yield. With a social discount rate of 10%, the effort should decrease by around 45-56% to achieve the optimal yield. The entry tax should be 92-279 USD/month/boat to achieve the maximum sustainable yield and 160-314 USD/month/boat to attain the maximum economic yield. Title: Sustainable Management of the Shrimp Trawl Fishery in Tonkin Gulf, Vietnam Author: Nguyen, Viet Thanh This study investigates the sustainability of shrimp stock in the trawl fishery in the Tonkin Gulf, Vietnam. It is a small scale and multi species fishery. The Verhulst-Schaefer and Gompertz-Fox surplus production models are applied. There are two shrimp spawning seasons in a year in the Gulf. Therefore, in this study, the surplus production models, associated to catch calendar and effort data, are applied for a half-year time interval. The results indicate that the fishing effort should be reduced by roughly 12-44% to achieve the maximum sustainable yield and 46-61% to reach the maximum economic yield. With a social discount rate of 10%, the effort should decrease by around 45-56% to achieve the optimal yield. The entry tax should be 92-279 USD/month/boat to achieve the maximum sustainable yield and 160-314 USD/month/boat to attain the maximum economic yield. Close