Bioeconomic Model Research Articles

Bioeconomic analysis of mackerel resources management (Rastrelliger sp.) at Malacca Strait, Serdang Bedagai Regency, Sumatera Utara

Mackerel (Rastrelliger sp.) is one of the main catch fisheries at Malacca Strait Serdang Bedagai, Sumatera Utara. This research aims to estimate mackerel (Rastrelliger sp.) resource potential with a bioeconomic model for mackerel resources sustainability landed at Tanjung Beringin. This research was conducted in July – September 2021. The method of research used the purposive sampling method. The surplus production method to estimate the Maximum Sustainable Potential (MSY) and the Gordon Schaefer Bioeconomic Model. The total sample fish of Indian mackerel were 272 individuals. The research showed bioeconomic analysis with Schaefer’s surplus production model approach shows that the optimum production rate is 359 tons and the optimum effort is 12148 trips. The Mackerel resources indicate to be biological overfishing.

Environmental assessment of mountain grassland farms with mixed cattle systems: use of bioeconomic simulations

Management practices of cattle farming systems must be improved, particularly to increase the systems’ feed self-sufficiency, food production and environmental performances. In mountain areas of the Massif Central (central France), mixed dairy/suckler cattle systems enable farmers to use grassland resources better and cope with economic fluctuations. Our objective was to estimate levels of ecosystem services provided by mixed dairy/suckler cattle systems as a function of the degree of mixing, along with their greenhouse gas emissions and energy use when their operation is optimized on an economic basis. The hypothesis was that mixed dairy/suckler cattle systems allow for controlled use of biomass, with better environmental performances than specialized systems (pure dairy or suckler herd) by maintaining grassland ecosystem services. Five herd-distribution scenarios were simulated using the Orfee bioeconomic optimization model. Environmental performances of the five systems were assessed according to three functional units (i.e., per farm, ha and kg protein produced). Mixed dairy/suckler cattle systems, which enabled larger herds, had higher greenhouse gas emissions per ha than specialized systems. However, because dairy cows produce more protein (milk and beef) than suckler cows, specialized dairy systems had the lowest greenhouse gas emissions and energy use per kg of protein. Specialized dairy systems had less advantage when dairy cows had less access to grassland. For the production of both milk and beef, mixed dairy/suckler cattle systems favour more sustainable use of biomass and tend to maintain a better combination of levels of ecosystem services for livestock production than specialized cattle farming systems.

Mitigation of greenhouse gas emissions in pasture-based dairy-beef production systems

CONTEXTAgriculture and food systems contribute significantly to climate change. Greenhouse gas (GHG) emissions intensity from beef production are high when compared to other livestock production systems and, therefore, mitigation of these emissions is urgently required. In many countries dairy-beef is making a large and growing contribution to total beef output thereby reducing net emissions given the lower emissions intensity of beef originating from the dairy herd when compared to specialized beef-cow systems. GHG emissions from dairy-beef systems can be further reduced by adopting best practice and mitigation technologies. OBJECTIVESThe objectives of this study were to (1) evaluate a range of management practices to reduce GHG emissions for pasture-based beef cattle production systems, (2) model the individual and combined impacts of these management practices on GHG emissions from dairy-beef systems, and (3) identify any trade-offs between GHG emissions mitigation, farm profitability, food security and land use. METHODSA farm level bioeconomic systems model was modified to evaluate spring-born, steer production systems finishing cattle at differing slaughter ages and from contrasting forage-based finishing diets (grazed grass or grass silage, each supplemented with concentrates). Mitigation measures included earlier slaughter age, optimal slurry management, urease inhibitors for nitrogen (N) fertilizers, replacing cereals with ‘by-products’ in concentrate feed rations and incorporating clover in grassland pastures. RESULTS AND CONCLUSIONSCombining mitigation strategies reduced dairy-beef systems GHG emissions intensity by an average of 21%. Incorporating clover in grassland pastures was found to be the most profitable stand-alone mitigation strategy increasing net margin by an average of 18%. Substituting by-products for barley in a concentrate ration converted all systems into net producers of human edible protein; otherwise, steer systems finishing at pasture during the third grazing season were the only net producers of human-edible protein. However, finishing at pasture during the third grazing season increased GHG emissions per animal and per kilogram of beef carcass. SIGNIFICANCEWithin a grass-based dairy-beef system, such as that modelled in this study, a number of complementary GHG emissions mitigation strategies can be implemented, without making substantive changes to the production system, while simultaneously improving farm profitability.

Breeding objectives for Central Highland goats using participatory and bio-economic modelling approaches.

The breeding objectives of Central Highland goats rearing under a low-input production system were defined through a participatory proportional piling method and bio-economic model. Additionally, the economic values and relative economic value of the breeding objective traits were derived. A participatory proportional piling method was used to estimate the relative weights of farmers attached to a list of goat traits identified, and the relative weights were statistically evaluated using a generalized multinomial logit model analysis. A bio-economic model was used to compute the economic values of the identified traits. The most important traits for selection of does according to farmer's preference were body size, coat colour, post-weaning growth rate and weaning rate with a relative weight (odds ratio) of 1.58, 1.38, 1.37 and 1.13, respectively. Goats with dark red followed by light red coat colour were the most preferred (p < 0.001) by goat keepers compared with white-coloured goats. Farmers were more likely (p < 0.001) to allocate higher scores for does-bearing twins than for single and triplet-bearing does. Using the bio-economic model (economic value and relative economic value), post-weaning growth rate, weaning rate, and six-month weight (body size) were identified as the most important traits and if the mean of these traits is changed by one genetic standard deviation, the change in profit will range from 2.06 to 3.03 $ doe-1 year-1 . Therefore, the most important traits for the selection of Central Highland goats according to the economic-based method were post-weaning weight gain, weaning rate and body size (six-month weight). Besides, coat colour was the second preferred trait by goat keepers next to body size. Thus, this aesthetical trait should be included in the designed breeding programme besides economically important quantitative traits. The combination of the participatory proportional piling method and bio-economic model would give better insights to explore the trait preferences of farmers and enhance profitability. The economic values of traits estimated in this study can be used for the construction of selection indices for Central Highland goats.

Assessing the Impact of Royalties on Fishery Resource

For the conservation of the fish population, a mix of legal, technical, social and economic instruments must be used, among which we find royalties. Beyond the fact that it is a source of budgetary revenue, depending on its amount, the royalty is meant to help avoid overexploitation of fishery resources, but within a mechanism that combines economic, social and environmental criteria. The modelling of this mechanism, as well as the evaluation of the ecological impact that it generates, represent the objectives of the approaches for conducting scientific research on this topic. To purely biological (based on maximum sustainable yield) and bio-economic models (which also take into account the fishing effort), we add an ecological model, which highlights, in the same plan, the economic, social and ecological optimum.

Cyanobacterial blooms management: A modified optimization model for interdisciplinary research

Controlling cyanobacterial blooms is a complex problem due to the biological features of cyanobacteria and the management objective of minimizing economic damages under a limited budget. Although bio-economic models provide hopeful methods for cyanobacteria control, the existing spatial-temporal optimization models do not consider both the heterogeneity of the natural loss rate of cyanobacteria in various growth stages as well as the heterogeneity of cyanobacteria spore migration between different regions. In this paper, we develop a new spatial-dynamic model to describe the reproduction and dispersal behavior of cyanobacteria. We consider the above heterogeneities and propose an integrated bio-economic optimization model as a valuable decision framework for water managers to allocate limited resources for cyanobacteria control. Specifically, our model incorporates maximum capacity constraints in terms of resource constraints, ensuring that cyanobacterial growth follows the fundamental biological principle of survival of the fittest. The potential applicability of our model is illustrated by a computational experiment. The results demonstrate that the investment exhibits diminishing marginal returns while allocating resources to the initially infected area can obtain the best bang for the buck under most test scenarios. This study is an interdisciplinary research that can assist managers in making more accurate decisions regarding budget allocation, the timing, and the location of cyanobacteria removal operations.

BUILDING INTEGRATED MODELS IN ENVIRONMENTAL AND NATURAL RESOURCE ECONOMICS: THE CASE OF GORDON’S 1954 FISHERY MODEL

Environmental and natural resource economics lies inherently at the interface between economic and natural dynamics (e.g., geological constraints, climate change, biodiversity evolution). Building models in that field often means building integrated models, calling on knowledge and methods from economics and physics, climatology, biology, or ecology. Howard Scott Gordon’s 1954 article on fishery economics is considered to be seminal in the history of bioeconomic modeling, integrating biological and economic variables in a microeconomic model. Yet the precise role played by biology in Gordon’s initial work remains unclear. On the basis of archival material and thorough analysis of Gordon’s early research, this paper examines Gordon’s model building and his persistent oscillation between two objectives—the production of a heuristic economic model with standard assumptions, and the conception of a predictive policy tool relevant from a fishery-biology standpoint—and how he finally favored the first over the second. Moreover, contrary to received wisdom, we show that it was not Gordon but biologist Milner B. Schaefer who transformed Gordon’s model into an integrated model. These results shed new light not only on Gordon’s 1954 contribution but also on a whole tradition of integrated environmental and natural resource economics models, based on his work.

Bioeconomic analysis of the commercial production of Nile tilapia with biofloc and green water technologies

This study presents a bioeconomic model after analyzing the commercial profitability of Nile tilapia under biofloc (BFT) and green water (GWT) technologies. Environmental stochasticity was evaluated using the parameters obtained in Yucatan's rainy (RN) and dry (DR) seasons. The productive impact was measured by analyzing the 10-year cash flow. Both systems demonstrated profitability with a positive NPV and 450 g harvest weight in the short term. The unit cost of production results for the GWT was lower than for the BFT. The long-term simulation involved an investment of $410,279 USD for 30 tanks, resulting in a positive return for GWT. BFT showed negative long-term profitability at the current selling price ($2.36 USD/kg). Profitability improved as the sales price increased by 11% and 22% for RN-BFT and DR-BFT, respectively. This bioeconomic model is pioneering in tilapia production in BFT and GWT and provides valuable data to achieve better yield and profitability.

Kajian Tingkat Degradasi dan Depresiasi Sumberdaya Ikan Layaran (Istiophorus platypterus) menggunakan Model Bioekonomi Clarke Yoshimoto Pooley di Perairan Utara Aceh

This study aims to assess the level of degradation and depreciation of the Layaran fishery in the North Coast of Aceh. The method used in this research includes stock assessment using the Clarke Yoshimoto Pooley (CYP) Bioeconomic model to assessing the degradation and depreciation that has occurred in the Layaran fishery. The estimated production value of the Maximum Sustainable Yield (MSY) is 4.63 tonnes per year which is greater than the actual production value of 3.33 tonnes per year and the MSY effort value is 36,642 trips per year which is greater than the actual effort 16,972 trips per year show that there has not been overfishing in the Layaran fishery, both in terms of production and fishing effort. Sailfish fisheries during the period 2009 to 2017 were also still in a non-degraded and depreciated condition as indicated by the coefficient values of the Degradation and Depreciation rates which were lower than the standard coefficient values with each value of 0.32 for the Degradation rate and 0.26 for the Depreciation rate.

Combining incentives with collective action to provide pollination and a bundle of ecosystem services in farmland

Bee decline and pollination deficit are driven by intensive agriculture and particularly pesticide use. So far policies to halt the decline and reduce pesticides have not unanimously been accepted, because they were not based on win-win solutions for farmers, beekeepers and biodiversity. A co-management of pests and bees is necessary, and in this study we tested if an incentive scheme based on beekeeper-farmer interdependency and collective action can lead to win-win solutions. We built a bioeconomic model to represent the mutual interdependency through pollination in intensive agricultural landscapes and simulate the economic and ecological impacts of introducing two beekeeping subsidies and one pesticide tax for different communication contexts. The model was calibrated using data from a study area in Western France. We showed that incentives affected targeted stakeholders, but also non-targeted stakeholders through a spillover effect, which therefore influenced the magnitude of ecosystem services provided at the landscape scale. We exhibited that communication between farmers and beekeepers amplified this spillover effect. Subsidies on beehives and honey led to win-win solutions for beekeepers and farmers since they had excellent pollination and economic performances, widely improved by communication. However, they were detrimental for other ecosystem services (ES) including pollination by wild pollinators. Conversely, tax on pesticides showed low economic performances, but was beneficial for the environment. Our study illustrates how a collective management of pollination is beneficial but warns against the artificialization of the pollination service that could result.

Bioeconomic analysis of stock rebuilding strategies for the green abalone fishery in Mexico under climate uncertainty

Globally, overexploitation of fishery stocks is a complex problem aggravated by climate change's effects. The green abalone in Mexico is an overexploited fishery, resulting in stakeholders committing to its recovery. Part of a comprehensive co-management strategy was to implement a fishing closure in some fishing areas. Now they are exploring reopening the fishery and gradually increasing fishing efforts. This research evaluates compatible management strategies with stock rebuilding under climate uncertainty. An age-structured bioeconomic model for the green abalone fishery was parameterized, which considered the impact of SST anomalies on population dynamics (i.e., recruitment, mortality, and growth). Three management strategies were evaluated under future climate scenarios (RCP 4.5, RCP 8.5, and a scenario without climate change). Results indicate that an effort level that aims to generate Maximum Sustainable Yield (MSY) based on historical fishery data may lead to overexploitation under warming scenarios. Instead, applying the minimum acceptable effort for the fishing community can support biomass recovery and is a strategy more resilient to climate change. This finding highlights the risk of overexploitation by assuming stock productivity stability under favorable climatic conditions when designing rebuilding plans. A stock rebuilding strategy will be more likely to succeed if it is cautious, recognizes uncertainties, and is flexible in considering stock productivity changes.

A behavioural agent-based modelling approach for the ex-ante assessment of policies supporting precision agriculture

Precision agriculture technologies can help reduce nitrogen losses and the associated negative environmental impacts. As the adoption rate of such technologies in small-scale farming systems is still low, additional policy measures are required to support their broader application. We provide an ex-ante assessment of policy measures (payments for reduced nitrogen, subsidy for the technology or area subsidies) to incentivize the adoption of sensing technologies for site-specific nitrogen fertilization with a specific focus on farmers' behavioural characteristics such as reluctance to change and their individual perception of the policy measures. We combine a bio-economic optimization model with data from a choice experiment, survey, and census data in an agent-based modelling framework. We simulate the impact of the policy measures on farmers' adoption decisions in Swiss wheat production. Simulations suggest that for the same level of nitrogen reduction a results-based payment (paying farmers for reduced nitrogen) is 1.5 times more cost-efficient than area-based subsidies and subsidies for technology use. Our results also suggest that considering how farmers perceive costs and benefits decreases the potential to reduce nitrogen input by ∼20%. We conclude that disregarding behavioural factors such as the perception of the instrument may result in a significant overestimation of the policy effect.

Combined Application of a Multi-Objective Genetic Algorithm and Life Cycle Assessment for Evaluating Environmentally Friendly Farming Practices in Japanese Rice Farms

When organic practices may have negative environmental effects, understanding the trade-offs between the economic and environmental outcomes of organic agriculture is essential in its promotion. This paper examines whether organic rice was planted in Japanese rice farms using the combined application of a multi-objective genetic algorithm and life cycle assessment. A modeled farm with 30 hectares (ha) of paddy fields is constructed using information from an agricultural management handbook. The planted crops considered are environmentally friendly rice with reduced use of chemical fertilizers and synthetic pesticides, organic rice, conventional wheat, and conventional soybeans. A bio-economic farm model with both economic and environmental objectives is created. The Pareto-optimal solutions indicate that the planted area of organic rice is 2.3 ha, at best, in the modeled farm. The cultivation of organic rice is likely to be constrained compared with that of environmentally friendly rice, and even though it produces an increase in income, it does not necessarily exert positive effects on the environment. The findings suggest that when organic farming has negative impacts, countermeasures against problems that emerge through its practice should be included in the essential requirements for subsidization.

Effects of harvesting and planktivorous fish on bioeconomic phytoplankton-zooplankton models with ratio-dependent response functions and time delays

This work presents a prey-predator model for plankton interactions in aquatic environments and the influence of planktivorous fish predation. Considering that some phytoplankton and zooplankton can be harvested due to their economic value, the time lag required for zooplankton gestation (representing the time delay) is included. The current study's main objective is to analyze planktivorous fish's influence on harvesting activity in both populations and the corresponding discrete delay (delay in zooplankton gestation) in the model. The stability characteristics of models with and without gestation delay are investigated, and the gestation delays threshold value is determined. The periodic solution's stability and the Hopf bifurcations' direction are determined by employing the center manifold theory. We use Lyapunov's method to investigate the global stability of the model without time delay. Bioeconomic equilibrium is obtained in three cases, each with certain conditions. In addition, the optimal harvesting strategy from the model is obtained by using the Pontryagin Maximum Principle and considering harvesting effort as a control variable. Finally, numerical simulations are performed to illustrate our analytical findings, and the ecological implications of our analytical findings are also discussed.

Does pig production improves cattle farm sustainability in the French massif central? A hierarchical constrained directional benefit-of-the-doubt approach

CONTEXTPig production systems are currently in decline in the French Massif Central, while herbivore production systems, most of which are specialised, generate little income. The diversification of herbivore farms with pig production appears to be an interesting lever for improving farm sustainability. OBJECTIVEThe objective of this study was to assess the impacts of adding pig production on the sustainability of beef and dairy farms and to assess the pros and cons of a DEA based multicriteria evaluation model. METHODSThe Orfee bioeconomic model was used to simulate 17 beef or dairy farms with and without pigs. This pig production system consists of either a farrow-to-finish sow production system or a pig fattening production system only. The structural and technical parameters of these farms were established from a farm survey. Farm sustainability was assessed using 17 indicators. These indicators were hierarchically aggregated into a single sustainability composite indicator using an innovative method, the constrained directional benefit of the doubt (D-BoD) method. RESULTS AND CONCLUSIONSThe results indicate that the addition of a pig production system has an overall positive impact on the sustainability of cattle farms. Mixed cattle-pig systems score significantly better on the social dimension as they generate more jobs and contribute more to food security. The overall economic performance is not significantly better than that of specialized systems for the price context from 2012 to 2022. The pig production system increases the average income per work unit for cattle farms but needs more purchased inputs to produce. This reduces but not offsets the risk reduction advantage of diversification and reduces production efficiency. Mixed farms do not score higher than specialized cattle farms on the environmental dimension. Mixed farms contribute less to global warming per kg of protein produced but have higher nitrogen and phosphorus surpluses. The constrained D-BoD method is a useful tool for endogenously aggregating indicators without having to arbitrarily set weights and thresholds to evaluate performance, but with certain limitations, such as the possibility that a farm may be judged efficient if it performs better on some indicators while being relatively weak on others. SIGNIFICANCEFavouring mixed farming appears to be an interesting lever for territorial development, but with two important issues: local supply of pig feed at a secure price and improved manure management to allow a virtuous cycle of nutrients.

Economic impact of investment in animal welfare–enhancing flooring solutions – Implications for promoting sustainable dairy production in Sweden

PurposeThe purpose of this paper was to assess the economic impact of investment in different animal welfare–enhancing flooring solutions in Swedish dairy farming.Design/methodology/approachThe authors developed a bio-economic model and used stochastic partial budgeting approach to simulate the economic consequences of enhancing solid and slatted concrete floors with soft rubber covering.FindingsThe findings highlight that keeping herds on solid and slatted concrete floor surfaces with soft rubber coverings is a profitable solution, compared with keeping herds on solid and slatted concrete floors without a soft covering. The profit per cow when kept on a solid concrete floor with soft rubber covering increased by 13%–16% depending on the breed. Practical implicationsPromoting farm investments such as improvement in flooring solution, which have both economic and animal welfare incentives, is a potential way of promoting sustainable dairy production. Farmers may make investments in improved floors, resulting in enhanced animal welfare and economic outcomes necessary for sustaining dairy production.Originality/valueThis literature review indicated that the economic impact of investment in specific types of floor improvement solutions, investment costs and financial outcomes have received little attention. This study provides insights needed for a more informed decision-making process when selecting optimal flooring solutions for new and renovated barns that improve both animal welfare and ease the burden on farmers and public financial support.

Management of multispecies resources and multi-gear fisheries: The case of oceanic tuna fisheries in Vietnam

The collapse of many marine fisheries is widely believed to result from mismanagement, which typically focuses on managing a single target species. The objective of this study is to assess the optimal management strategy for multispecies resources and multi-gear fisheries, with a specific application to oceanic tuna fisheries in Vietnam. We utilize the Monte Carlo method (CMSY) and Bayesian State-Space (BSM) approach to evaluate the stock status of skipjack tuna (SKJ) (Katsuwonus pelamis), yellowfin tuna (YFT) (Thunnus albacares), and bigeye tuna (BET) (Thunnus obesus) in Vietnam’s sea waters. Additionally, we establish reference points for tuna fisheries by utilizing bioeconomic models and tuna fishing data from longlines (LL), gillnets (GN), and purse seines (PS) for the period of 2000–2019. The findings reveal that SKJ and YFT stocks are overexploited, while the BET stock is not overfished in Vietnam’s sea waters, even though there have been warnings of overfishing in the Western and Central Pacific Ocean. The tuna fishing effort has exceeded sustainable fishing effort, and the current effort of PS and GN fisheries should be reduced to attain optimal stock and harvest levels. It is also necessary to implement policies that shift fisheries from the current unsustainable situation to a situation where fishing effort corresponds to the reference points. This paper offers a useful foundation for devising a suitable management plan for the sustainable management of tuna fisheries, particularly for non-members of the regional fisheries management organizations.

A model of a fishery with fish storage and variable price involving delay equations

We propose a bio-economic model of a fishery describing the variations of the fish stock, the fishing effort and the price of the resource on the market supposed to depend on supply and demand. The originality of this model comes from taking into account the storage of part of the resource for a certain time before being put up for sale on the market. Taking into account the supposedly fast price dynamics compared to the other mechanisms involved and after integration of the stock equation, the system is reduced to a system of two delayed differential equations. The qualitative analysis of the model is carried out with the search for equilibrium points and the study of their stability. The study shows the existence of a catastrophic equilibrium corresponding to the extinction of the resource and one or two sustainable fishery equilibrium points that can coexist under certain conditions. The model shows that storing part of the resource makes it possible to avoid a catastrophic situation with the extinction of the fish stock and to stabilize the fishery in the long term. The study also shows that the price variation of the resource has a stabilizing effect by avoiding the appearance of periodic solutions associated with a stable limit cycle surrounding a sustainable fishery equilibrium point resulting from a Hopf bifurcation, which is contrary to the case without price variation where this is possible.

The economic potential of organic production for stockless arable farms importing biogas digestate: A case study analysis for western Germany

CONTEXTMost stockless organic farms depend on the import of organic nitrogen. Biogas digestates offer an interesting solution to address this need for flexible nitrogen fertilizers. Their application could support the conversion of specialized arable farms, contributing to the politically targeted expansion of organic production. However, various regulations on the use of off-farm biogas digestates exist, which differ considerably in allowed N imports. Despite the growing interest in the application of biogas digestates in stockless organic farming in practice and research, its impacts on the economic potential of converting from conventional to organic farming have not been investigated. OBJECTIVEThis study assesses the economic potential of organic production for specialized arable farms without taking up animal production based on cooperating with a conventional biogas plant. The study considers the impacts of different regulations on importing off-farm biogas digestates. METHODSThe assessment employs the bio-economic farm model FarmDyn to evaluate multiple economic performance indicators for three stockless arable case study farms with varying cropping patterns under conventional and organic production. The German federal state of North Rhine-Westphalia serves as the case study area. A large-scale sensitivity analysis quantifies the impact of relevant parameters with a high uncertainty or possible large impact. RESULTS AND CONCLUSIONSOur results suggest that organic farming has a high economic potential for specialized arable farms when biogas digestate is applied. Taking existing subsidies into account, organic farming economically outperforms conventional production for all assessed farms and regulatory scenarios. However, stronger restrictions on the application of biogas digestates shift crop rotations toward higher shares of crops with low nutrient requirements and legumes. This reduces, especially in case of fodder legumes, revenues and increases labor requirements, and lowers profitability and labor productivity. Distance to the biogas plant and subsidies for organic production impact strongly on profitability, whereas input prices show small effects. Results underline that the economic performance of stockless organic farming depends highly on import possibilities of nutrients. Furthermore, they suggest that subsidies for organic farming should better reflect its economic potential across farm types to reduce deadweight effects and boost conversion where it is costly. SIGNIFICANCEThe study is the first to assess the impact of different regulations governing the import of fermentation substrates on the economic potential of stockless organic farming for specialized arable farms. This is relevant as conversion of stockless arable farms is lagging behind but could considerably contribute to reach policy targets for organic production.

Optimal effort, fish farming, and marine reserve in fisheries management

In this paper, we develop a bioeconomic model to determine an optimal wild catch harvest and freshwater commercial aquaculture production in a lake that uses cages or floating rafts. Although off-bottom aquaculture activities have less impact on the environment compared to on-bottom aquaculture, it has negative externalities. It takes away the fishing area and hence creates pressure in the open-access fishing ground. It also changes the nutrient and ecological composition of the environment. We recommend the implementation of a reserved area to minimize the impact of fishing and aquaculture activities. The reserve also helps in improving the habitat and restocking the fish population which is declining rapidly. We determine the optimal sizes of the aquaculture and reserve and the optimal effort level that maximizes social welfare. We illustrate our findings using numerical simulations and perform an analysis of the optimal solutions with respect to biological and economic parameters involved in the model.