Theoretical Model for Circular Plastic Practices in the Fishing Industry

Abstract

Plastic from abandoned fishing gear can persist in the marine environment for extended periods, worsening the problem of ghost fishing and highlighting the urgent need for sustainable solutions. This research aims to develop a theoretical model that defines the socio-economic costs and benefits of fisheries within the context of the circular economy. The theoretical foundations of the model are based on moral risk theory, externality theory, and welfare economics. Marginal analysis, cost–revenue function analysis, and investment efficiency analysis were also used. According to the results, the costly process of catching, transporting, and collecting lost fishing gear carried out by fishermen can be replaced or offset by implementing several proactive measures. These include introducing compensation to encourage fishermen to adopt pro-ecological practices related to reducing the amount of used fishing equipment. The proposed model could be a helpful tool in determining the optimal level of subsidies for sustainable fisheries. The model could also help determine the costs and methods of reducing the pollution associated with fishing gear, which is vital for all entities currently operating in the fishing sector.

1. Introduction

Throughout history, fishing gear and related equipment have often been lost at sea. However, in the past, these marine tools were typically made from natural materials that quickly decomposed, posing little threat to marine life. However, the advent of modern technology and gear design has led to a reliance on synthetic materials, particularly plastics such as nylon, polyethylene, and polypropylene [1]. These synthetic materials, resistant to biodegradation, can remain in the marine environment for a long time, worsening the ghost-fishing problem and underlining the urgent need for sustainable solutions.

As Hammer et al. [2] emphasize, plastic is a modern material that offers many benefits and many dangers at the same time. Among the advantages, the authors mention the durability and strength of plastic, as well as the relatively low cost of its production. On the other hand, there is no doubt that plastic has a negative impact on flora and fauna, including the marine environment. Moreover, the costs of its disposal after use are high, affecting more than just the economy. The improper management of plastic waste has resulted in it being released into the environment and entering the world’s oceans [3]. Plastic ending up in seas and oceans poses both an environmental hazard and negatively impacts the performance of the on-board systems of many ships [4]. Ghost fishing refers to abandoned (derelict) fishing gear, which accidentally catches fish and other marine animals even after it is no longer actively used by fishermen [5]. Ghost fishing poses a serious threat to various aquatic species, including those that are susceptible to fishing gear-related issues and highly desirable for commercial purposes. The problem has attracted widespread attention from both politicians and the media due to its high mortality rate. In addition, ghost fishing can lead to the spread of toxins and microplastics in marine food chains, the introduction of invasive species, the proliferation of harmful algal blooms, and damage to key habitats. This not only affects the safety of people at sea, but also reduces the socio-economic value of coastal and near-shore regions [6].

It can be challenging to determine the exact range of ghost fishing on a global scale, but recent research provides some estimates that may help shed light on the issue. A recent analysis by Richardson et al. [7], which covered fishermen from seven major fishing nations, found that 2% of the fishing gear used worldwide ends up in the ocean. Although this percentage may seem small, the scale of global fishing is vast. This translates to some 3000 square kilometers of gillnets, 740,000 km of longline mainline, and 25 million traps and pots. If the current rate of losses continues, the number of lost fishing nets measured in terms of area would be enough to cover the surface of the planet within 65 years. As a result, the WWF [8] estimates that the number of species affected by entanglement or ingestion of plastic debris has doubled since 1997, from 267 to 557 species. This affects 66% of marine mammals, 50% of seabirds, and all seven species of sea turtles.

Reducing the amount of waste generated from fishing gear is therefore a global problem. Rashid et al. [9] emphasize that the issue of plastic pollution requires interdisciplinary solutions. The involvement of various stakeholder groups is needed at the production, use, and waste management stages. Political action should be supported by scientific research. Through educational campaigns, individuals and communities can actively participate in reducing the amount of plastic. It is broadly understood that cooperation can reduce the adverse effects of plastic use and protect the environment for future generations. It is also worth emphasizing that the recycling of plastic waste from the sea has emerged as one of the ways to minimize plastic pollution, but it is associated with high costs. However, it is worth considering due to the possibility of material recovery and energy production. Therefore, combined pro-environmental technologies and a circular economy are inseparable in reducing microplastics in the seas [10]. In terms of utilizing waste from fishing gear, the concept of the circular economy can fulfill both restorative and regenerative functions by minimizing energy costs through the use of renewable energy sources, while reducing the negative impact of microplastics and maximizing benefits [11,12].

Researchers conducting studies in different parts of the world (Brazil, the United States, Latvia, Estonia) indicate significant gaps in knowledge on the type, quantity, and sources of abandoned, lost, and discarded fishing gear [13,14,15]. Therefore, basic mitigation measures should include educational programs on the ecological consequences of abandoning fishing gear. Solutions for better enforcement of environmental protection law are also needed [14]. Additionally, there is a need to investigate and implement effective mechanisms for monitoring derelict fishing gear and waste management activities [15,16]. Appropriate incentives for fishermen to return loaned fishing gear are also indicated, which also requires research and analysis [17].

To fill at least part of this research gap, this study aims to develop a theoretical model of the socio-economic costs and benefits of fishing within the context of the circular economy, thereby contributing to the debate on addressing the global problem of lost and abandoned fishing gear. The novel approach taken in this study involves assuming that the linear economy is insufficient in proposing solutions to the challenge of used fishing gear, and efforts need to be redirected towards a circular economy, which offers a more comprehensive framework.

The paper is structured as follows: Section 2 provides the research context related to the three issues—marine litter from fishing gear, a circular economy pertaining to fishing gear, and the possibilities of material recovery and energy production from this waste. Section 3 presents the research method used. Section 4 assesses the possibilities of reducing the amount of microplastics in fishing gear. Section 5 discusses the results. Section 6 presents the study’s conclusions.

2. Marine Litter Comprising Fishing Gear and the Need to Reduce It

2.1. Marine Litter Comprising Fishing Gear

Among the plastics ending up in the seas and oceans, a particularly problematic fraction of waste is abandoned or lost fishing gear [18]. As indicated by Lee et al. [19], more than half of marine litter consists of waste from fishing nets, which, years after being released, continue to pose a significant challenge to coastal and aquatic ecosystems.

Lost, abandoned, and discarded fishing gear in the seas and oceans is considered a global socio-ecological problem [20,21]. The causes of this problem may vary. Often, these are unfavorable ocean or sea and meteorological conditions, but the lack of education and awareness among fishermen is also significant, as well as the poor waste management infrastructure both on board and on land [22]. Fishing gear may also be lost as a result of interactions with wild animals and entanglement in an obstacle on the seabed [7]. In addition, poor fishing practices and a lack of adequate infrastructure for the disposal of fishing gear can also significantly contribute to the abandonment of fishing gear at sea or in the ocean [14]. In recent decades, abandoned fishing gear has become an increasingly significant component of marine litter [23]. This is a result of both the increase in the size and fishing effort of global fisheries and the switch to synthetic and more durable materials from which fishing gear is made [24].

Abandoned fishing gear has many negative ecological consequences. The most well-known problem is ghost fishing—gear abandoned in water bodies for years or decades can still catch and kill aquatic animals [24]. Cetaceans are most affected by entanglement, followed by sea turtles, fish, and seabirds [21]. Other equally dangerous and negative consequences include the transfer of toxins and microplastics into marine food webs, the transport of invasive alien species, the spread of micro-algae, the destruction of coastal and marine habitats, the obstruction of ship navigation, and damage to used fishing gear and submarine cables [6,24,25]. In addition to the ecological consequences, lost or abandoned fishing gear can cause negative economic impacts on coastal areas. Abandoned fishing gear carries with it a number of potential economic losses, including impacts on commercial fisheries, impacts on coastal property values, and costs to local governments and voluntary organizations associated with the removal and disposal of marine litter. These losses also apply to “existence” values related to environmental pollution [26].

Over the last decade, there has been a growing international awareness of the need for multilateral efforts to address the transboundary negative ecological and socio-economic impacts resulting from the loss and abandonment of fishing gear [6]. A variety of measures have been implemented to mitigate the problem of used fishing gear. They have been most commonly divided into preventive or ex ante measures and curative or ex post measures. Although both types of tools are fundamental, experience has shown that more emphasis is placed on curative tools [1].

The Goodman report [27] on mitigation actions recommends, among others, large-scale gear-recovery operations; facilitating the collection of decommissioned gear; implementing a recycling system to prevent waste from going to landfills; and involving all stakeholders in the process of finding and properly disposing of fishing gear. Similarly, Tschernij et al. [28], in their study on lost fishing gear in the Baltic Sea, suggested four basic actions that can improve the existing situation. These actions include mapping areas where dead nets accumulate, removing dead nets from these areas, developing an optimal recycling method or management system for fishing gear retrieved from the sea, preventing the problem by reducing the number of nets lost during fishing, and ensuring fishing gear is easily identifiable. Macfadyen et al. [1] also propose that in the field of therapeutic interventions, attention should be focused on the need to locate lost fishing gear; report lost gear to existing reporting systems; recover lost gear; and dispose of fishing gear economically, safely, and responsibly.

2.2. Fishing Gear in the Context of the Circular Economy

The circular economy has attracted the interest of both academics and practitioners, as it is seen as a means of operationalizing economic practice to implement the concept of sustainable development [29]. Thus, circular economy is an attempt to conceptualize the integration of economic activity and environmental well-being in a sustainable manner [30]. The circular economy includes an alternative economic system, shifting the end-of-life approach to recycling and alternative reuse. In a circular economy, recovery cycles cover production, distribution, and consumption processes. Alternative activities should encompass all levels of the economy—micro (products, companies, consumers), meso (eco-industrial parks), and macro (local, regional, national, global)—to achieve sustainable development aimed at creating environmental quality, economic prosperity, and social equality, for the benefit of present and future generations [31]. The transformation towards a circular economy requires changes in the value chain, from the product design stage to a new business and market model, and from new methods of transforming waste into resources to new behavioral practices [32].

In the context of the circular economy, from the perspective of fishing gear production, methods that reduce the risk of gear loss in the water are crucial. One solution is to implement a gear-marking program that will facilitate the monitoring and reporting of gear found at sea [27]. In this regard, it is important to develop and promote inexpensive and sustainable methods for identifying the manufacturer’s name, year of production, product type, and production batch, as well as key elements of the gear, e.g., ropes, net panels, and traps [17]. In this regard, it is also important to pilot the introduced methods for marking fishing gear. In this regard, it is crucial to examine the current practices used by fishermen and to raise fishermen’s awareness of net marking [33].

In the production of fishing gear, the material used is also important. Considering the principles of the circular economy, biodegradable materials suitable for use in aquatic environments should be researched and utilized. In this respect, it is about using materials that have a predictable and controlled rate of degradation. Additionally, it is crucial to limit the use of durable materials (e.g., mixed-polymer materials) and the adoption of new technologies in biodegradable materials for various types of fishing equipment and accessories [17]. According to Drakeford et al. [34], the use of biodegradable gear by fishermen is not so much an economic problem as a technical one. One of the main problems is reduced fishing efficiency. Reducing this problem would contribute to the increased popularity of more environmentally friendly fishing gear.

The Goodman report [27] also highlighted the need for tightening regulations on vessel traffic and shipping lanes to reduce interactions between vessels and gear. Richardson et al. [7], who conducted a study in seven countries around the world (Belize, Iceland, Indonesia, Morocco, New Zealand, Peru, and the United States of America) showed that in order to prevent the loss of fishing gear effectively, the following actions should be taken: maintenance of fishing gear, limiting the interaction of active gear with wildlife, reducing the financial and administrative burden on port reception facilities, shortening the length of voyages, and marketing educational and gear management programs towards fishermen with limited awareness of marine litter, particularly in fisheries and low-income countries. In the report by Macfadyen et al. [1], preventive actions focus on reducing gear loss, including tagging gear, using GPS and transponders to monitor gear, facilitating the collection and disposal of gear, and establishing restrictions on transported gear.

In the process of using fishing gear, cooperation with management bodies is also necessary to track the origin and ownership of recovered gear, as well as to locate lost gear. In addition, appropriate incentives for fishermen to return loaned gear are also necessary. Such actions also require innovative research and development to improve the management of fishing gear. Considering the end of the product cycle, preventive actions can refer to innovative research and development for better ways of recovering fishing gear, as well as to provide convenient, safe, and relatively inexpensive forms of disposal of unused fishing gear in ports. Therefore, it is necessary to facilitate and promote the recycling of fishing gear and its proper disposal. Actions in this area can refer to reducing the buy-back of old gear for refurbishment, as well as recycling or obtaining new equipment. Additionally, it is crucial to support the implementation of effective schemes for the disposal of fishing gear [17].

In the report by Giskes et al. [33] on good practices for the end of life of fishing gear, it was suggested that the local community be involved in the collection of fishing gear and community banks be created (buying fishing gear from fishermen and providing additional income to the community that collects and cleans fishing gear). The report also emphasized the need to provide training on recycling fishing gear to the local community. It was also considered important to create incentives for fishermen to participate and properly dispose of fishing gear to prevent its loss or abandonment. It is also important to provide fishermen with economically viable options for the proper disposal of used fishing gear. To ensure the effectiveness of the actions, all stakeholders, i.e., fishermen, vessel owners, fishing authorities, NGOs, and fishing gear manufacturers, should be involved in the process.

In addition, Savels et al. [16], based on research conducted in the Republic of Cyprus, advocate the implementation of a waste management policy (plastics), particularly for used fishing gear, and the intensification of information campaigns on fisheries’ policies and regulations. They also point to the need to implement a tracking and recovery system for fishing gear and a deposit refund system for fishing gear. Similarly, Gallagher et al. [22], based on research on lost fishing gear in Sri Lanka, recommend changes in national and international policies, as well as direct national involvement in this issue.

2.3. Material Recovery and Energy Production from Marine Waste from Fishing Gear

Conventional disposal methods, such as landfills or incineration, make it impossible to recover valuable materials [19] and close the cycle of individual products in the fishing industry. According to Eimontas et al. [35], the collected waste can serve as an alternative raw material for producing additional energy products with higher added value.

One area of interest for researchers in the field of fishing gear management is the recovery of caprolactam, a nylon compound. As indicated by Eimontas et al. [36], the recovery of this fraction saves natural resources, maximizes the economic efficiency of fishing gear, and closes the economic cycle in the fishing net industry. According to the method proposed by the authors, it is possible to recover this fraction in a highly efficient manner and utilize it for the production of nylon fibers, thin nylon films, carpets, textiles, resins, and in other applications. Also, Ryou et al. [37], conducting research on energy recovery from fishing gear waste, suggest that the proposed solution may help to solve the problem of marine pollution.

Choi et al. [38] conducted research based on fishing nets collected in a Korean port and proposed thermochemical conversion for the direct valorization of waste. According to the authors, this process can be used for the direct processing of plastic waste by obtaining energy as a form of synthetic gas.

Nugroho et al. [39] observed the possibility of utilizing synthetic waste from fishing gear as a raw material for producing liquid fuels, which can serve as an alternative energy source. Lee et al. [19] proposed an innovative way of converting used fishing gear into hydrogen to solve problems associated with marine nets. The authors expect that their research will contribute to the transition to a low-carbon economy based on hydrogen, which will meet the growing demand for energy while promoting waste recycling.

However, analyses of specific case studies conducted by Adelodun [40] suggest that pyrolysis outperforms other methods of plastic processing. The liquid and gaseous fuels produced by these processes create value from waste. Therefore, this process requires further optimization and intensification to help free the planet from burdensome plastic waste, while improving the economy and meeting energy demand.

Apart from recycling waste from abandoned fishing gear, another issue worth mentioning is the noticeable reduction in the amount of this waste. The life-cycle assessment (LCA) of abandoned fishing gear provides interesting conclusions in this regard. As Kuczenski et al. [41] emphasize, the diversity of fishing gear makes it challenging to clearly assess the environmental risk; however, such analyses can be found in the literature. Kuczenski et al. [41] proposed a model for fishing gear use intensity. Schneider et al. [42] analyzed the potential environmental impact of recycling fishing gear waste to identify the most appropriate waste management system. According to the results, the method of disposing of fishing gear as hazardous waste can be replaced by mechanical recycling or energy recovery. Wilde Tippett [43] assessed the life-cycle of recycling waste fishing ropes—from rope acquisition to the production of recycled granules to delivery to the customer. According to the results, the primary factor influencing the environmental impact of the rope recycling system is the production and consumption of diesel fuel at various stages of the life-cycle. It is worth emphasizing that, despite the possibility of recycling, researchers agree that preventing the generation of marine litter from abandoned fishing gear should play a more critical role. Such actions are perceived as more effective in mitigating negative environmental impacts [41,42,43].

It is worth noting that recycling plastic waste presents many practical challenges. First and foremost, these processes are expensive and not consistently effective. Collecting and transporting plastic waste can be a complex process. Transport does not always occur in environmentally friendly conditions, especially considering the global trend of waste being transferred from wealthier to poorer countries. One of the challenges of waste disposal is the potential for toxic substances to leak. Reducing this process requires significant investment. Another problem is the gradual loss of quality during the recycling process, which poses a challenge for reuse. Hence, reducing the amount of plastic waste is crucial [44].

2.4. Multilateral Cooperation in the Management of Fisheries

However, in order to properly manage the growing amount of plastics from the sea (e.g., for renewable energy purposes), solutions are needed from both the business and government perspectives. Government action should consist of creating policies including the approval of initiatives or energy recovery from microplastics. In addition, legislation should be created and enforced against marine plastic pollution, recycling should be promoted, and alternatives to plastics should be sought to reduce their use [2]. Additionally, the government should also implement economic instruments in the form of appropriate subsidies and tax deductions. From a business perspective, there is a need to develop improved technologies for more efficient and effective processes of energy recovery from microplastics [10].

Policy implementation and stakeholder cooperation in the fishing industry is a complex issue, partly due to the diverse needs of individual stakeholders. Schwermer et al. [45] emphasize that a holistic approach to fisheries management is increasingly being adopted by the European Common Fisheries Policy, as well as by individual countries that benefit from aquaculture. The authors identified several key stakeholder groups in fisheries policy: the fishery, politics, science, eNGOs, others (e.g., local businesses), related industries, the public (community members, representatives from public organizations, consumers), and recreational fisheries. Stakeholder engagement is a key element of policies regarding fisheries. However, such an orientation requires taking into account the experiences, needs, and interactions of diverse stakeholder groups in decision-making processes.

Stöhr et al. [46] report positive experiences of co-management among various stakeholders in fisheries, based on examples from Poland and Sweden. Collaboration between stakeholders contributed to building trust, shared dialog, and mutual learning in both cases studied. It is worth emphasizing that similar results were observed, despite the differences between the Polish and Swedish situations, both in ecological, socio-cultural, and political terms.

Msomphora [47] analyzed the case of Norway, pointing to the need for broadly understood cooperation between stakeholders. Their research findings revealed a complex and controversial landscape in coastal zone management, as well as relatively weak stakeholder engagement. The author highlights the need for multifaceted solutions that integrate the enforcement of environmental regulations, inclusive management processes, and local and cultural knowledge.

Analyzing the situation in the United States, Siddiki and Goel [48] emphasize the importance of multilateral cooperation, involving various stakeholders, both governmental (federal, state, local) and non-governmental (e.g., private, non-profit, or university). Cooperation in the marine aquaculture policy process provides an opportunity to exchange knowledge, both specialist knowledge regarding the local situation and legal expertise. This helps identify appropriate solutions that take into account the interests of various stakeholders.

In real life, cooperation between stakeholders should be based on regular dialog, allowing all interested parties to express their views. According to research conducted by Stöhr et al. [46], meetings organized for various fishery stakeholders play a crucial role in fostering dialog. Rules and procedures in dialog should be defined in advance of planned meetings. Meetings should be organized in widely accessible locations, preferably connected to local authorities, ports, and scientific or business institutions. The chairpersons of such meetings should be qualified and at the same time neutral, acting as mediators. It is crucial that, in addition to experts in the field of fisheries, science, and law, fishermen also have the opportunity to speak out, express their opinions, and clarify doubts.

3. Methods

The presented research adopts a theoretical approach, proposing a socio-economic model of the costs and benefits of fishing within the context of the circular economy. The research is divided into three basic stages, implementing the research aim in each.

The first stage addresses the moral hazard associated with marine plastic pollution from fishing gear. The theoretical framework for this stage is based on the moral hazard theory [49,50,51] and the externality theory [52,53,54], which analyze the propensity of fishermen to discard plastic back into the sea.

The second stage involves determining the costs and benefits of fishing. The proposed model was based on the theoretical assumptions of welfare economics [53,54,55,56] and the theory of the firm [57,58]. Marginal analysis [52,59,60], cost–revenue function analysis [50,51], and fishing activity were also assessed and used.

The third stage includes a proposal for a system of incentives for fishermen to adopt pro-ecological behaviors. The theoretical basis for the incentive system was mainly determined by marginal analysis [52,59,60] and investment efficiency analysis [50], assessing in what situations pro-ecological behaviors would be profitable for fishermen.

4. Reducing Microplastics from Fishing Gear—A Theoretical Model of the Socio-Economic Costs and Benefits of Fishing

4.1. Fishing Costs

Fishermen often encounter significant amounts of plastic waste trapped in their nets. Upon returning to port, they are required to manage this plastic responsibly, ensuring that it is delivered for further processing. In this scenario, society reaps almost all the benefits of cleaner oceans, while fishermen bear the brunt of the costs and inconveniences. Faced with this inequality, it becomes tempting for them to throw the plastic waste back into the waters on which they depend for their livelihoods. The economics of moral hazard sheds light on such situations, highlighting how one party can engage in risky behavior when the repercussions primarily affect the other party [49,50,51]. In the case of a fisherman struggling with plastic waste in his trawl, this theory can explain the tendency to throw the trash back into the ocean rather than undertake the onerous task of proper disposal.

This circumstance reveals a glaring cost–benefit imbalance: when fishermen pull plastic waste from the deep, they incur significant costs in both time and money for proper disposal of that waste. Such costs can include additional fuel needed to transport the plastic, valuable fishing time lost to waste management, and potential disposal fees. In stark contrast, fishermen may see only marginal benefits, such as poor financial incentives or, in many cases, no direct economic reward. The more significant benefit—a cleaner marine environment that the community deeply desires—flows to society as a whole, while individual fishermen remain largely unrewarded.

Moreover, the apparent lack of incentives exacerbates the problem. As fishermen bear the burden of waste-disposal costs without receiving fair compensation or adequate incentives to participate in responsible disposal practices, the drive to achieve the goal decreases. This creates a worrying scenario in which the immediate temptation to throw plastic back into the ocean seems more attractive than the arduous process of proper disposal. Cost externality complicates the situation even further: the negative effects of throwing plastic back into the ocean—such as pollution and damage to delicate marine ecosystems—do not have a tangible impact on the fisherman. Instead, these consequences are imposed on society, which must face the consequences [52,53,54].

Fishing involves various costs [60,61], which can be divided into three main types: capital costs, operating costs, and pollution costs. Capital costs refer to the investment in physical assets such as fishing vessels and equipment. Operating costs encompass all current operating expenses, whereas pollution costs are associated with environmental degradation resulting from fishing activities. Pollution costs can be further divided into two subcategories: microplastic pollution and costs resulting from the loss of fishing gear. On the other hand, costs related to the loss of gear can be quantified as an expected value. The total socio-economic costs of fishing c(h) can be formulated as follows:

$$c\left(h\right)=k\left(a\right)+r\left(h\right)+m\left(h\right)+p\left(h\right)·l+o$$

where h—number of fishing hours; k(a)—capital costs; a—total investment in vessels and equipment; r(h)—operating costs; m(h)—expenditure related to microplastic pollution; p(h)—probability of losing fishing gear; l—economic loss resulting from the loss of fishing gear; o—other costs.

In this context, c(h) denotes the total socio-economic costs. The term k(a) indicates the capital costs, where a represents the total investment in vessels and equipment, including any reinvestment made during their operation. Meanwhile, r(h) includes the operating costs and m(h) consists of the expenditure related to microplastic pollution, which is influenced by the number of fishing hours. In addition, there are costs associated with the loss of fishing gear, calculated as the product of the probability function p(h)–which depends on the number of fishing hours—and a value l that reflects the economic loss incurred (including losses due to ghost catches) in case of gear loss. In addition, o includes other related costs. The cost function will vary depending on the type of boat and needs to be adapted to the case under consideration.

Levelized Cost of Fishing (LCOF) is a useful concept for developing an incentive system for the fishing fleet. Based on the equation, LCOF can be defined as follows:

$$LCOF={\displaystyle \frac{NPV \left(k\left(a\right)+r\left(h\right)+m\left(h\right)+p\left(h\right)·l+o\right)·A}{h}}$$

where NPV—net present value; h—number of fishing hours; k(a)—capital costs; a—total investment in vessels and equipment; r(h)—operating costs; m(h)—expenditure related to microplastic pollution; p(h)—probability of losing fishing gear; l—economic loss resulting from the loss of fishing gear; o—other costs; A—annuity factor.

LCOF provides a measure of the cost of fishing for one hour in money units. The LCOF enables the calculation of a single indicator that comprehensively considers the costs incurred per hour of fishing. The LCOF is a helpful tool in assessing the use of different types of fishing gear, also taking into account the variable conditions in different waters (e.g., through different probability of losing fishing gear or other operating costs). Because it includes pollution costs, the LCOF defined here represents the socio-economic costs.

4.2. Marginal Costs and Marginal Welfare Gains

Fish stocks must be managed in a way that achieves and maintains the maximum sustainable yield. This refers to the largest catch that can be taken from a specific fishery over an indefinite period of time under constant environmental conditions without causing population declines. However, the exact definition of maximum sustainable yield can vary across marine areas and is influenced by many factors, including ecological conditions, species interactions, and most importantly, the extent and type of plastic pollution present in the ocean [62].

Given n possible measures available and limited resources, the overarching goal should be to allocate resources in a way that optimizes overall social welfare [43,44,45,46]. A fundamental principle of economic efficiency is that the marginal welfare gain per monetary unit spent on all chosen means should be equalized [60]. This approach maximizes the positive impact of the investment while addressing the urgent problem of ocean plastic pollution.

Defining U_i as the welfare gained by spending xi money units on measure i, the marginal increase in welfare, i.e., tonal welfare gained for each additional unit spent on measure i, is given by ${\displaystyle \frac{{dU}_i}{{dx}_i}}$; in order to achieve optimal resource allocation, it is necessary to ensure that

$${\displaystyle \frac{{dU}_1}{{dx}_1}}={\displaystyle \frac{{dU}_2}{{dx}_2}}=\cdots ={\displaystyle \frac{{dU}_n}{{dx}_n}}$$

where U_i—welfare gained by spending xi money units spent on the measure i; ${\displaystyle \frac{{dU}_i}{{dx}_i}}$—marginal increase in welfare.

In general, increasing investment in a particular measure often leads to diminishing marginal benefits. After a certain threshold, it becomes more efficient to direct resources toward other measures that offer higher marginal benefits. That is, as long as one measure provides greater marginal welfare per unit spent than another, resources should be reallocated from the less efficient option to the more efficient one. If the marginal costs are lower than the increase in marginal welfare, resources should be allocated to the measure.

4.3. Revenue and Cost Function for Unregulated and Regulated Fishing

In the case of unregulated fishing, fishing is free and everyone seeks to maximize profit [57,58], so fishermen participate in fishing as long as they earn money from it. In this case, the annual total catch measured in money, y, depends on the size of the fish stock, s, and the number of active fishing boats, b. In the model, the price is constant and equal to p = 1 per unit weight of fish. With these assumptions, the following relationship can be established between the total revenue y, the size of the stock s, and the number of active fishing boats b:

$$y=f(s,b)\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{y}_s^{\prime }>0\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{y}_b^{\prime }>0\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{y}_{bb}^{″}<0$$

where y—annual total catch measured in money; s—size of the fish stock; b—number of active fishing boats.

Each boat owner will assume that he is, on average, as successful as everyone else. That is, he expects his share of the income from fishing to be equal to the average income per boat, i.e., y/b. The boat owner further assumes that he has the exact costs as everyone else if he sends a boat out fishing. If the cost per boat is w, the boat owner will send a boat out fishing if he makes a profit from doing so, i.e., if y/b > w, but will reduce his catch if y/b < w. Given these assumptions, we can obtain the equilibrium solution b₀, where

$${\displaystyle \frac{y}{b}}=w\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\Rightarrow \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}y=wb$$

where y/b—average income per boat; b—number of active fishing boats; w—cost per boat.

Regulated fishing aims to maximize annual catch. The firm will seek to maximize profit. Then, the firm will maximize the profit function.

$$\pi =f\left(s,b\right)-wb\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\Rightarrow \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{f}_b^{\prime }-{\left(wb\right)}_b^{\prime }=0\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\Rightarrow \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{f}_b^{\prime }=w$$

where s—size of the fish stock; b—number of active fishing boats; w—cost per boat;

The firm maximizes profit by adjusting so that marginal revenue equals marginal cost. Figure 1 shows that the firm’s optimal solution is to change so that the number of boats equals b₁. The line m is parallel to the cost line y = wb. This means that line m has a slope w, which equals marginal cost. Marginal revenue equals the slope of the revenue function y = f(s, b). At point h, marginal revenue equals marginal cost. Therefore, b₁ must be the number of boats that maximizes the total profit from fishing. If every boat pollutes equally and the goal is to reduce pollution, regulated fishing to maximize annual catches is better than free fishing, in which everyone can catch as much as they want.

4.4. Pollution Reduction Costs

If a company (e.g., a fishing boat) wants to reduce its emissions of environmentally harmful substances, it will incur costs. In economic theory, marginal costs are often modeled as increasing functions [52,59,60]. The costs of reducing emissions are usually modeled similarly: the more emissions are already reduced, the more expensive it becomes to reduce them further. Figure 2 illustrates the marginal costs of reduction, representing the cost of reducing pollution by one unit. If the company has not reduced its emissions at all, the emissions are equal to X. The first steps in emission reduction will cost very little, but the costs increase as more emissions are reduced. Completely eliminating emissions incurs significant cost. The red line illustrates the scenario where a new technology is developed that makes reducing emissions less expensive.

In terms of fishing boats, there are many ways to reduce emissions. They can reduce the number of fishing days. Although production is decreasing, plastic pollution is also decreasing. Another option is to change the type of equipment or collect used equipment—both that which you own and that which has been abandoned.

4.5. Upgrading and Selecting Fishing Gear

According to the initial assumption, equipment X is manufactured from plastic materials that release microplastics during use due to wear. According to the second assumption, it is possible to mix biodegradable material with the raw materials used to produce X, allowing for any mixing percentage from 0% to 100% to be achieved. The amount of microplastic released (z) is a function of the mixing percentage (n). This gives z = g(n). As the mixing percentage m increases, plastic pollution decreases. We can therefore set z′ < 0. The biodegradable material does not have the same strength as plastic, so the new version of X will not have the same lifespan as X without mixing. This means that X with a high mixing percentage needs to be replaced more often than X without mixing. The cost (c) of using X is therefore an increasing function of the mixing percentage. This means that c = c(n), where c′ > 0, assuming that both z and c are reversible functions such that

$$z=g\left(n\right)\hspace{0.25em}\hspace{0.25em}\Rightarrow \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}n=h\left(z\right)\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}c\left(h\left(z\right)\right)\hspace{0.25em}\hspace{0.25em}\Rightarrow \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}{c}_n^{\prime }=c_n^{\prime }·h_z^{\prime }<0$$

where z—amount of microplastic released; n—the mixing percentage of biodegradable and raw materials; c—cost of use.

There is a relationship between mixing speed and costs. The marginal costs of increasing mixing speed increase. There is a direct relationship between mixing speed and the reduction in plastic pollution (reduction). Figure 3 contains two curves: the marginal cost of reduction and the marginal benefit of reduction [52,59,60]. The economically optimal reduction in pollution is shown by A*. Upon reaching that point, costs equal benefits. Typically, pollution reduction is not free. As long as the reduction is lower than A*, the marginal benefit of reduction is lower than the marginal cost of reduction.

According to the initial assumption, all companies, including fishermen, seek to maximize profits. When companies make investments, they perform investment calculations and choose the investment alternative with the highest net present value (NPV) [60]. A fisherman can choose high (improved)-quality or low-quality fishing equipment. The price for high-quality equipment (U_H) is higher than the price for low-quality equipment (U_L). On the other hand, maintenance costs (E_H and E_L) are higher for low-quality equipment than for high-quality equipment. According to the assumption, buyers of high-quality equipment receive a subsidy at the time of purchase and/or annual support S_H. On the other hand, those who buy or use low-quality equipment are charged an upfront fee at the time of purchase or annually T_L. In order for the purchase of good-quality equipment to be profitable, the following conditions must be met:

$${NPV}_H<{NPV}_L$$

$${NPV}_H=U_H+\sum _{t=1}^n{\displaystyle \frac{E_H}{{(1+r)}^t}}-\sum _{t=1}^n{\displaystyle \frac{S_H}{{(1+r)}^t}}$$

$${NPV}_L=U_L+\sum _{t=1}^n{\displaystyle \frac{E_L}{{(1+r)}^t}}+\sum _{t=1}^n{\displaystyle \frac{T_L}{{(1+r)}^t}}$$

where H—high-quality equipment; L—low-quality equipment NPV—net present value; E—price for equipment; C—maintenance costs; S_H—subsidy for high quality equipment; T_L—fee for lowa quality equipment.

NPV_H and NPV_L are the net present values of costs, including support or fees. The incentive system must ensure that this condition is met. The result can be generalized to any situation in which a firm can choose between environmentally friendly or environmentally unfriendly investment alternatives.

4.6. Subsidization

In terms of subsidizing pro-ecological fishing activities, it is worth considering three examples: limiting fishing days, selecting more environmentally friendly equipment, and collecting used equipment. Situation A means pro-ecological practices, and situation B constitutes traditional fishing without these practices. In the case of limiting the number of fishing days in situation A, the fisherman incurs the opportunity costs of lost profits.

Similarly, the choice of gear type can involve additional costs. Gear type A, which is environmentally friendly and produces minimal pollution, contrasts sharply with gear type B, a traditional option that contributes significantly to marine litter. Gear type B is characterized by its reliance on plastic components, which exacerbates the pollution problem. Additionally, the non-polluting gear type A is made of natural fibers. While this eco-friendly choice is commendable, it presents the fisherman with a number of financial challenges. Compared to the commonly used gear type B, gear type A is significantly more expensive, has a shorter lifespan, and tends to wear out more quickly. In addition, this gear requires more frequent repairs, is more difficult to operate, and is less efficient at catching fish. These factors combine to create a significant financial burden for the fisherman, who should be encouraged to make an environmentally friendly choice.

Similarly, one can consider the options of traditional fishing— one without collecting old gear (B), and the option of fishing in a more ecological manner and collecting used gear, not only that which you own but also that which has been abandoned (A). Therefore, it becomes necessary to calculate the appropriate amount of subsidy, which will compensate these increased costs and encourage the transition to more sustainable fishing practices. The following formula can express subsidy per year (S_Y):

$$S_Y={AC}_A-{AC}_b$$

where AC_A stands for the annual cost of situation A; AC_B stands for the annual cost of situation B.

Fishermen who choose environmentally friendly alternatives should be compensated for the additional costs they incur, as well as any potential loss of income due to reduced catch efficiency. The scale of the subsidy will vary depending on the specific fishery, taking into account the significant differences between trawler operations, which use large nets to catch fish, and longlines, which deploy baited hooks over large distances. Furthermore, a well-designed incentive system should also include a fee that reflects the socio-economic repercussions caused by pollution, ensuring that those responsible contribute to the restoration and protection of our marine ecosystems.

5. Discussion

To reduce the amount of plastic being released into the ocean, several proactive measures can be implemented. Consideration could be given to compensation schemes that provide financial incentives for fishermen to responsibly deliver plastic waste to designated waste management facilities, as well as establishing a more equitable distribution of waste-disposal costs, potentially financed through public funds or fees to cover handling costs.

Incentives for more sustainable fishing practices can help improve the situation in terms of closing the loop in the fishing industry. However, this requires an appropriate approach from both the theoretical and practical side. From the fishermen’s perspective, the key issue concerns the higher costs associated with implementing more ecologically friendly fishing practices. Considering that fishing as a business is focused on profit, incentives that compensate for additional costs may be a good solution. This is in line with the views presented by both science and practice in this area [16,17,33].

The incentive system should be implemented at various stages of the fishing gear cycle in the fishing industry (Figure 4), as well as in actions taken to reduce the amount of plastic in the seas, starting with the production of equipment from biodegradable materials or mixtures, which is the first step to reducing the amount of microplastics. The distribution of equipment should be accompanied by incentives to purchase better, more environmentally friendly equipment, ensuring that fishing activity remains profitable. As part of fishing activity, incentives should concern limits on fishing days. Reducing fishing activity will also reduce the amount of microplastics in the seas. Pollution that has already occurred can be limited by incentives to collect it. These actions should apply to both a fisherman’s own waste from used equipment and abandoned equipment from others. Collected old equipment can be disposed of or recycled—recovering valuable materials and energy. This option fits perfectly into the concept of the circular economy. It is worth adding that modern technologies enable such energy recovery and production [19,36,37,38,40].

To successfully introduce modern fishing gear to the market, cooperation with fishermen, fishing organizations, and researchers is necessary to test and improve the design and materials of the gear. This cooperation can have a positive impact on both the effectiveness and acceptability of new gear [17].

An important action in reducing the amount of plastic from fishing gear is to increase awareness and train fishermen in good practices and proper fishing. This necessity is emphasized by both scientists and practitioners [7,17,33]. These actions can help address the issue of limited awareness and education among fishermen in this area [22]. The need for close cooperation with management bodies at various levels is also indicated [17,22,33].

This study addresses the problem of marine pollution, a challenge that is recognized worldwide but difficult to quantify and highly context-dependent. As such, a notable limitation of this study is its general applicability, which often requires adaptation to specific types of equipment, local conditions, and constraints. However, this limitation is also consistent with the chosen research design and should be seen as an impetus for further research.

Further research requires validation of the proposed theoretical model. Future directions include pilot studies to collect statistical data, as well as conducting surveys and interviews with fishermen and managers. A cost–benefit analysis combined with a life-cycle analysis (LCA) constitutes an important element of further research, taking into account different fishing gears. Future research should provide context-based evidence on the practices effectively implemented by different stakeholders to address marine plastic pollution.

6. Conclusions

Technological advances in the fishing and aquaculture industries have led to an increased reliance on plastics. Because these materials are resistant to biodegradation, they pose a significant threat to the aquatic environment in the event of lost fishing gear. Therefore, there is an urgent need to implement more sustainable production patterns, which aligns with the implementation of SGD 12 (responsible consumption and production). In this context, the article proposes a theoretical model of the socio-economic costs and benefits of fishing within a circular economy, assuming support for activities that mitigate negative environmental impacts.

Establishing an appropriate incentive system for the fishing fleet is essential. Fishermen have the opportunity to catch, transport, and dispose of lost fishing gear, but this process is currently both expensive and unprofitable. Furthermore, the benefits of ocean cleaning are mainly accrued by society as a whole. Several proactive measures can be implemented to mitigate the issue of plastic pollution in water bodies. These include introducing compensation schemes to encourage fishermen to dispose of plastic at designated waste management facilities properly. Additionally, a more equitable distribution of the costs associated with removing waste from water bodies should be established. The proposed activities may prove crucial to achieving SGD 14 (life below water). These actions combine not only sustainable fishing and sustainable resource use, but also building awareness of the importance of protecting the seas and oceans.

In terms of practical implications, a wide range of fishery stakeholders can benefit from the proposed model. The primary target audience is fishermen, as well as government officials and other relevant stakeholders. This model can become a tool to help determine the optimal level of subsidies for sustainable fishing, and can also help determine the costs and methods of reducing pollution related to fishing gear, which is important for all stakeholders in fisheries today—fishermen, local and national authorities, residents, and environmental protection institutions. This information may be particularly helpful to fishing gear producers, given the growing emphasis on developing more environmentally friendly equipment. Scientists can also use the model for further consideration, discussion, and development.