Could Deep-Sea Fisheries Contribute to the Food Security of Our Planet? Pros and Cons

Abstract

Hundreds of millions of people on the planet are affected by malnourishment. This contributes to the vulnerability of large swaths of the population worldwide. Children under five years old and adolescent girls are especially disproportionately vulnerable to diseases and even death in less developed countries. Today, by providing a substantial share of global protein intake, as well as fatty acids and micronutrients, fisheries contribute to global food security. As fish stocks in the upper sea levels are increasingly over-exploited, there is a surge in discussion on the potential contributions of deep-sea fisheries for global food and nutrition security. Some mesopelagic fishes show potential in providing important nutrients. Another way of supplying food security might be in using mesopelagic fish as fish feed. However, fishing in the mesopelagic zone could lead to severe ecological repercussions, especially because the impact on the biological carbon pump is uncertain. This paper highlights and juxtaposes different perspectives regarding exploitation pathways of the fish riches of deep seas, and reviews best practice model projects that deal with uncertainties related to fishery management in the mesopelagic zone. The review concludes that due to the essential role of the mesopelagic zone in the global biological carbon pump and complex interaction patterns between pelagic and mesopelagic species, exploitation of the fish riches of the mesopelagic zone must be based on comprehensive data and rigorous analyses. In the face of the current uncertainty on the respective mechanisms, the authors endorse an international moratorium on deep-sea fisheries and/or the rather small-scale exploitation of mesopelagic biomass.

1. Introduction

Fisheries and aquaculture play a central role in the assurance of global food and nutrition security [1,2]. Despite its importance, there are grave challenges related to the sustainable management of fish stocks around the world. The available fish stocks of the pelagic zone are inexorably declining due to overfishing, illegal fishing, pollution, and the degradation of marine ecosystems [2,3]. The supply, which is especially important for food security, is involved with underlying threats regarding sustainability and aquatic ecosystems [4]. Anthropogenic pressure on the natural environment inevitably rises, leading to global concerns regarding food security and biodiversity loss. Mesopelagic fishery is a field whereby the conflict between environmental costs and short-term economic benefits comes to its own [5]. Climate change will also have an uncertain effect on the ecology of oceans, their species composition, and the productivity of fisheries [3].

Food and nutrition security is one of the key global policy goals today [4]. More than 800 million people suffer from chronic hunger, and as the population on Earth rises, food production needs to increase as well [6]. The conventional fishery management models focus mostly on purely economic aspects and ignore the issues of food and nutrition security and human welfare [7]. Against the backdrop of the significance of the mesopelagic zone for the biological carbon pump and its potential contribution to the resilience of food security, the question of mesopelagic fishery management must be analyzed from the lens of socio-ecological economics. Hence, when drawing policy recommendations regarding mesopelagic fisheries, in addition to improved food security, poverty alleviation, and sustainable yield, ecological aspects must also be incorporated into this discussion [2,4,8].

In recent years, there has been increased interest in the opportunities and risks related to the exploitation of the biomass of the mesopelagic zone [2]. Mesopelagic fish live in the world’s oceans 200 to 1000 m below sea level. Large-scale biomass estimates are rather scant, and the importance of mesopelagic fish on the ecosystem and carbon sequestration is overwhelmingly underresearched [9]. The knowledge gaps that exist, as well as international policies and governments that may not be capable enough of managing a new kind of commercial fishery with these unique characteristics, might lead to grave socio-economic and ecological repercussions [10]. The question of distributional justice also plays an important role because the economic benefits of the rollout of mesopelagic fisheries would probably disproportionately benefit a few countries, as well as large-scale fisheries that would not contribute to increasing income or food security of the local communities in developing countries [11].

The paper addresses the features of the mesopelagic zone, the exploitation of its biomass, and the resulting risks and opportunities for sustainable development. The paper is organized as follows: Section 2 presents the employed methodology of this review paper. Section 3 provides a comprehensive review of the literature on the potential role of the Twilight Zone in the assurance of global food security. Section 4 briefly presents the major ongoing initiatives that explore fish biomass and the potential effects of deep-sea fisheries. Section 5 elaborates on policy implications, and Section 6 concludes.

2. Methodology

This study reviews the existing literature on the status quo of the mesopelagic zone and deep-sea fisheries and assesses the research, exploration, and certification initiatives on the mesopelagic fisheries. Within the literature review, we analyze the works on global food security, biological carbon pump, employment effects of the deep-sea fisheries development, and the interactions of the pelagic and mesopelagic fish species and their alterations because of harvesting biomass from the mesopelagic zone. We do not confine ourselves to the scholarly sources indexed in the Scopus and Web of Science (WoS) databases and also integrate the reports of international organizations such as FAO and Marine Stewardship Council (MSC) into an analytic review. The special focus of the study is in the first line of the literature on the uncertainties related to the rollout of mesopelagic fisheries.

More data on the effects of deep-sea fisheries is required to develop more reliable decision support systems that would enable mesopelagic harvesting that would lead to Pareto optimal solutions in terms of food security, global climate, and biodiversity. In addition, the interests of small-size fishers, their employment, and food and nutrition security must also be incorporated into decision support systems for a full-scale or partial ending of the moratorium agreements. Based on the systematic analysis of the mentioned sources, the authors will try to derive policy recommendations for the future of the explorations and exploitations of the Twilight Zone.

3. Deep Sea Fisheries and Global Food Security

Fisheries play a crucial role in combating hunger and an important role in employment in impoverished coastal communities in developing countries [12]. However, pelagic fish stocks around the world are often times exposed to the risk of overexploitation and extinction [12,13]. This is not congruent with the vision of the long-term contribution of deep-seas to global food security and fighting malnutrition [14]. Recent estimates suggest that the mesopelagic zone could contain up to 10 gigatons (Gt) of fish biomass [15,16,17]. The existing estimations are, however, subject to grave uncertainties and knowledge gaps regarding the biomass in the mesopelagic zone and the ecosystem involved [10]. The following sub-section discusses the importance of fisheries for food security and the benefits and costs of mesopelagic fisheries.

3.1. The Link between Fisheries and Food Security

There are 800 million people on the planet that are malnourished [18]. One of the main goals in our modern society is the provision of nutritious food in a world with close to two billion people suffering from deficiencies such as vitamin A, iron, and zinc. Oceanic food is one of the options to meet this need, especially as fish is highly nutritious and, from a climate perspective, superior to meat [6]. Since a major part of the earth is water, the ocean represents a large potential for biomass [18]. More than 70% of marine production is directly used for human food [3].

The link between fisheries and food security may be complex, as the availability of fish may not intuitively lead to increased food security. The availability of food supplies is not the only factor influencing food security. Social science research states that food security is composed of four pillars. These pillars include food availability, food access, food utilization, and food stability. Trade may also be a key determinant of food security. People may wish to contribute to their own and others’ food security directly but also draw income from trading fish to other food commodities, increasing food security indirectly [19].

Research on food security focuses on the interdependent socio-ecological relationships that are involved with food systems in terms of options to build resilient food systems for the provision of long-term food security. The focus of the literature on fisheries’ role in food security is on Western countries, but increasingly aims towards developing countries within which farmers and fishers are increasingly losing local control over food systems [20]. Analyses of the publications in Scopus since 1954 show that within the last five decades, there has been an inexorable increase in research and the accumulation of knowledge on mesopelagic zone, as shown in Figure 1. These studies are, however, not analyzed in the context of food security. There are only 5 works out of 3019 publications on mesopelagic zones in Scopus that focus on the potential effects of mesopelagic fisheries on food security [2].

Also, for the studies on the role of mesopelagic zone in the biological carbon pump, we can observe an increasing research interest. Figure 2 shows that, especially since the mid-2000s, the number of studies on the ecological aspects of the mesopelagic zone has been linearly increasing.

Fish are an important source of micronutrients and animal proteins [21]. Almost seven percent of the entire amount of proteins consumed by humans originates from fish products. Fish also contains minerals such as iron and zinc, as well as long-chain omega-3 fatty acids, which are important in human dietary needs [6]. Animal protein consumption is correlated with the per capita income (PCI). Among wealthy countries, few rely on fish as the main supply of animal protein; however, this is the case for many low-income countries. Countries with a PCI of two thousand dollars or less rely more than twenty percent on fish as the main animal protein supplier. A decrease in fisheries’ catches may be linked not only to missed sources of healthy, varied, nutrient-rich food but also to losses in maternal and child welfare, as well as reductions in disability-adjusted life expectancy via the likelihood of risks of coronary heart diseases [5,21].

For instance, in the South China Sea, including the Gulf of Thailand and Tonkin in the Pacific Ocean, it is still one of the main economic activities for the coastal communities living there [5]. It provides not only livelihood but also employment and products for trade. Marine fish contribute 15 to 65 percent of animal protein in this area. One of the main downsides of fishing in the South China Sea remains the over-capitalization, especially in China, Taiwan, the Philippines, and Thailand, as attempts to limit fishing have failed and fisheries remain mostly unrestricted. Global demand, in line with poor governance, may lead to a decline in marine resources and costs for society.

In Southeast Asia, some governments encourage fishing exports with the downside of risking domestic food security [5]. That fish is not only linked to food security in Asian or developing countries but was also described in Moore and Nesbitt [22] in a follow-up study. The authors showed that the issue is of relevance for Indigenous food security as well. Indigenous people are also considered to be very vulnerable to biodiversity loss, as it is a major component of Indigenous food security [22].

Kristen N. Lowitt [20] examined the relationship between changing fisheries and community food security on the west coast of Newfoundland in Bonne Bay. The study responds to the recognized need for more interdisciplinary approaches to the complex interrelations and involved problems around food security and fisheries. Many fishing policies treat seafood as a commodity vs. human food, with the shortcoming of the importance of seafood within the food system and the communities’ well-being [20]. McIntyre et al. [1] focused on fishery management for global food security and biodiversity conservation. The authors constructed a joint analysis of fish consumption and economic status, indicating that poor people and malnourished populations rely a great deal on freshwater fisheries. To analyze this, the authors created an index of nutritional dependence on fisheries based on the role of fisheries in total animal protein consumption [1,2].

As food security is a central concern for many countries living close to the ocean, one might consider changing not only the productivity of individual stocks of fish but also the total biomass in the ocean and the total catch derived from that biomass. By using 224 stocks of fish, Cody S. Szuwalski [23] proposed in 2016 that the average decadal change in productivity overall stocks by biomass remained close to unchanged, rather than showing a negative trend in productivity if the stocks were not weighted means but equally weighted to all stocks, regardless of size. Unweighted means are, however, not useful when concerned with the conservation of particular fish stocks [24]. Instead of only fishing in the upper zone of the oceans, with increasingly diminishing fish supply, deep-sea fisheries are increasingly targeted and discussed [24]. However, targeting new deep-water opportunities goes along with rising environmental and management concerns [25,26].

3.2. Mesopelagic Fisheries as a Source of Healthy Food

If exploited responsibly, mesopelagic zones have the potential to become an important contributor to global food security and nutrition [6,12,13,15,16]. The idea that deep-sea fisheries could become commercialized was already proposed in the 1960s. However, worldwide annual mesopelagic fish catch was just slightly above 10 megatons between 1970 and 2015 and is mostly harvested from the North and South Atlantic and the Indian Oceans [10].

The mesopelagic zone includes 60 percent of the earth’s surface, as well as twenty percent of the volume of the ocean [10]. Mesopelagic fish live in the twilight zone of the oceans and are rather small, with a typical size below 20 cm. The fishes are very likely to be the most abundant vertebrates, with the biggest stock of deep-sea fish being lanternfish [9]. It was also claimed that mesopelagic fishes as a whole may be the most abundant source of food in the entire biosphere, making them especially interesting in terms of fisheries [27]. The biomass hotspots, such as the Kaikoura Canyon, might be one potential future commercial fishery target, as it has substantial amounts of biomass, and there are estimated to be more than one hundred such hotspots in the ocean [28,29].

Species within the mesopelagic zone that undertake daily migrations upwards usually live in waters around 500 to 800 m depth; species that do not migrate mostly remain at depths of 700 m or deeper [11]. Most deep-water fishes are identified to have slow growth rates, high longevity, and late maturity; however, a number of traits are not known yet [30]. Lanternfish (myctophids) consist of a family of approximately 250 different species that are fairly abundant and are eaten by many commercially exploited fisheries [10]. There is little information about the nutritional contents and values of different deep-sea fishes compared to commercial fishes, making it hard to evaluate the potential as a new form of food source [6]. As mesopelagic fishes are small and could be consumed in their entirety, they might be more efficient for food consumption as they have a higher productivity per unit biomass than large fishes [14].

Further investigations of some mesopelagic species suggest a potential for fishery exploitation, especially glacier lanternfish (Myctophid Benthosema) and Mueller’s pearlside (Maurolicus muelleri), as they contain high levels of lipid and fatty acids, making them interesting for diverse purposes. However, the large-scale exploitation of such fishes definitely needs to be assessed with regard to their economic and ecological impacts first [31]. The fishes living in that zone of the ocean play a substantial role in biogeochemical cycling via extensive daily vertical migration, with a large amount of fish feeding on nutrient-rich surface waters under the cover of darkness and sequestering carbon when respiring at depth [9]. There are possibly several mechanisms linked between mesopelagic fishes and carbon cycling.

Without deep-sea fishes, atmospheric carbon dioxide might be up to 50 percent greater than the currently observed level [11]. However, quantifying carbon fluxes from primary production to deep-sea fishes is one of the main challenges in assessing the role of mesopelagic organisms in the biological carbon pump and their influence in affecting climate in the following decades [32]. In addition to the ecosystem services, potential by-catch stocks, food web interactions, and biodiversity need to be considered when talking about mesopelagic exploitation [31].

As deep-sea fishes may be one of the least investigated fractions of the entire ocean ecosystem, with severe gaps in understanding of biology and adaptations, state-of-the-art scientific research is not even certain about the global biomass [2,27]. Early net-based mesopelagic fish biomass estimates are likely to be underestimates [9]. First estimates using acoustics and local estimates in the northeast Pacific come to the result that estimates should be one order of magnitude higher than prior biomass estimates suggested [28]. Estimations for mesopelagic fish are 1000 million tons with approximately 70 to 191 Megatons in the Southern Ocean [9]. Others suggest a total biomass of 9 to 19.5 Gigatons, equal to approximately 100 times the per year catch of all currently existing fisheries [32]. Estimates based on food web models estimate a biomass of 2.4 Gigatons.

These uncertainties regarding the biomass in the mesopelagic zone show the general uncertainties associated with the mesopelagic zone. It is known, however, that most deep-water fishes are identified to have slow growth rates, high longevity, and late maturity [30]. Many traits that are not known, such as fish swim-bladder volume, length distribution, and different fish species morphology, are also still unclear and need further research [32]. Fishing mesopelagic species might also be involved with high costs, as the fishes are located in great depth and are recognized to show trawl avoidance behavior [18].

On the other hand, most mesopelagic fish species are low-value species, and therefore only economical in the sense that one fishing trip has to be involved with large-scale catch rates due to economies of scale. Increased harvesting leads to increased Pony catch rates and high profits [33]. An evaluation of the economic performance of potential future mesopelagic fishery was conducted by Paoletti and his co-authors [31]. Prices of Mueller’s pearlside fish would probably be around that of Herring prices, as the fat content is similar and linked to the price.

Fishing costs would probably be similar to the current blue whiting fishery due to similar trawls needed. Additional costs may, however, arise as vessel modifications or new vessels might be needed for efficient deep-sea fisheries. From a solely economic point of view, mesopelagic fisheries’ expected increased costs in comparison to revenues will not be too extensive to obtain profitability with the current fleet. However, ecological sustainability needs to be considered first [31]. Also, catch quotas of commercial species will be limited soon, leaving excess capacities in commercial fisheries that may be taken for fishing for mesopelagic fishes [32].

From the nutritional and food security perspectives, the findings suggest a remarkable potential for the mesopelagic zone. Alvheim et al. [6] published a paper in 2020 analyzing six different species of mesopelagic fishes that are commonly found in deep Norwegian fjords, concerning their potential significance towards food security. Two fish species, three shellfish, and one jellyfish were studied regarding their nutrient contents. Micronutrients found in the sample were high but may be partly due to including all parts of the fish sample. All species, except the jellyfish, contained large amounts of calcium and iodine. Fatty acids were also plenty, and especially high in the lanternfish species. Iron and zinc levels were also pronounced in the samples. The authors claim that mesopelagic fishes therefore have the potential to fight iron deficiency, which is associated with lower scores in cognitive achievements in school children and lower work productivity in adults. In addition to being nutrition-dense food sources, the mesopelagic fishes may also be taken for feed ingredients in aquaculture, as sustainable aquaculture is also a challenge today [6]. Another study also provided nutrient composition data of fish species, including mesopelagic biomass from the EAF Nansen program. Nordhagen et al. [34] published a paper in 2020 where they sampled different fish species on the coast of Bangladesh to determine their potential contribution towards nutrient intake.

Comparing pelagic, mesopelagic, and demersal zone fishes, they found that demersal species had lower nutrient concentrations, and mesopelagic fishes had greater concentrations of nutrients. Almost all species, except demersal ones, contribute to sufficiently high vitamin B, different acids, and selenium, and all contribute to more than 25 percent of the recommended nutrient intakes. Among all available fish species, two mesopelagic fish species, namely the spiny cheek lanternfish and unicorn cod, contain the greatest values in iodine, calcium, iron, vitamin A, and selenium. However, due to unknown concentrations of undesirable substances such as wax esters, mesopelagic fishes may be unsuitable for direct consumption but rather used for fish feed [34]. It remains, however, clear that small fish eaten whole have higher nutrients per weight than big fish, as they have higher micronutrients [35,36].

Mesopelagic fishes are rather small fishes. Hence, there might be a large potential for food security and nutritious security [18]. However, many things about mesopelagic fishes remain unclear, and further research is needed [32]. The number of potential fishes that may be exploited in the mesopelagic zone led to nations therefore spending substantial funding on research, such as the EU and Norway. The United States in the past prohibited commercial fisheries in the deep sea due to potential adverse ecosystem consequences [11]. In the following section, some of these projects regarding mesopelagic fisheries will be demonstrated.

4. Projects on Mesopelagic Fisheries

As the mesopelagic zone is, to a great extent, unexplored and the consequences of commercial fisheries unknown, there is a range of projects and initiatives set in motion to observe, monitor, and identify different aspects of the mesopelagic zone [10]. The potential effects of harvesting mesopelagic fish could significantly improve the nutritional status of vulnerable population groups around the world. However, the exploitation of mesopelagic biomass could detrimentally affect the global biological carbon pump and the carbon absorption capabilities of world oceans. This calls for more efforts in reducing these uncertainties via funding of large-scale exploratory research in this realm [28].

Ecologically and Economically Sustainable Mesopelagic Fisheries (MESSO) is a research project funded by the European Union’s Horizon 2020 research program with more than 6 million euros [37]. It is coordinated by the Institute of Marine Research (IMR) in Norway, running from 2019 to 2024, via ten work packages. The aim of the project is to close the knowledge gaps within the marine ecosystem of the mesopelagic and whether it can be exploited in an economically and ecologically sustainable manner. The implementation of new acoustic and trawling technologies will try to collect better estimates of fish species, as well as the interactions and functioning of marine ecosystems, which are currently not sufficiently known. Also, the mapping of contaminant and nutrient content of mesopelagic species will be explored to analyze the potential for viable fisheries. From these insights, the project tries to gain information and knowledge to draw conclusions about the trade-offs between exploitation and negative impacts on the ecosystems. In the second step, the collected data and insights will be used to identify options for sustainable governance [37].

Another project funded by the European Union is SUMMER, with the main goal of evaluating if and to what extent mesopelagic resources may be exploited without harming the essential ecosystem services that they provide. There are nine work packages, with most of them having started in 2019 with a duration until 2024. The project aims to estimate the biomass of mesopelagic fishes, quantify bycatch, measure the role of food webs, and estimate carbon sequestration. Furthermore, it was implemented to explore the potential of mesopelagic species towards human food and animal feed and to ensure that there will be strategies and responsible management of mesopelagic resources with strategies toward sustainability. Short-term impacts are proposed to be the increased knowledge of the mesopelagic ecosystem, the contribution of the United Nations agreement toward effectively regulated marine harvesting, as well as the preservation of the ecological functioning of the deep sea. Furthermore, the project tries to foster innovative concepts toward food and nutrition security [38].

There are also other examples of recent initiatives to explore the potential for mesopelagic fisheries and the potential markets. Two other projects funded by the European Union with the EU Horizon 2020 are named MESOPP and PANDORA. Mesopelagic Southern Ocean Prey and Predators (MESOPP) consists of a collaboration between Australian and European researchers with the aim of investigating how climate change will affect exploitation in the Southern Ocean and Antarctica. The Paradigm for New Dynamic Ocean Resource Assessments and Exploitation (PANDORA) consists of 25 research teams trying to analyze long-term benefits for European fisheries by developing different methods for mesopelagic fisheries. Other than European Union funding, there was a Norwegian mesopelagic initiative in 2017, where researchers collaborated to develop sustainable mesopelagic fishing. The participants improved gear and developed new technologies to give those mesopelagic fishes that were caught accordingly with a sustainability label [11]. Also, to increase knowledge about deep-sea fishes and get insights into sustainable management practice, the Norwegian Institute of Maritime Research launched a project called Unleashing new marine resources for a growing human population. For this purpose, trial fisheries, with licenses for experimental fisheries, were carried out in international waters, such as the Northeast Atlantic [33].

5. Policy Implications and Limitations

As with all natural resources on the planet, fish stocks are finite, and therefore, pertinent legal frameworks, international cooperation, and novel deep-sea fishery policy management models are indispensable [29]. A scientifically valid stock assessment is vital for the elaboration of applied sustainable fisheries management. This is, however, not currently available due to the limited scientific knowledge of the mesopelagic zone [10]. Aware of the uncertainties, the exploitation of biomass needs appropriate assessments of options to sustainably manage and govern this potential.

The interactions between ecological, social, economic, and governance systems need to be understood, and a robust governance system needs to be established [2]. The central challenge for the development of a deep-sea governance system is the incorporation of all stakeholders into these governance models. The authors recommend the management of the global mesopelagic fish riches within the framework of an independent body based on the model of the Extractive Industries Transparency Initiative (EITI) with global consumers as a central stakeholder within this body. This, in combination with the certification of the sustainability certification of the seafood, could contribute to more inclusive and considerate deep-sea fishery models. To this end, we suggest the extension of the activities of the global multi-stakeholder Fishery Improvement Project (FIP) that deals with the environmental sustainability of fisheries to the realm of mesopelagic zone, too.

Biological trade-offs and risks involved with mesopelagic exploitation need to be weighed against the potential benefits. New technological developments in fishing methods fitted for mesopelagic resource harvesting, as well as investments are needed too [31]. Harvesting from this ecosystem can indeed supply more food, but the potential consequences associated with biomass extraction on the role of the deep sea in climate regulation, conservation, biodiversity, and ecosystem stability have to be very well considered and call for a precautionary approach to protect mesopelagic fish species [32]. There is also a need for high-quality representative data on the different nutrient contents of mesopelagic fishes. Even if Nordic countries have food-based dietary guidelines, the guidelines should be more nutrition-sensitive. Mesopelagic fishes may very well contribute to nutrient-dense food sources. However, the nutrient composition might vary, and as commercial deep-sea fisheries are at an early stage, further nutrient investigation of mesopelagic fish species is needed to predict nutrient profiles and draw information from them [6]. Heretofore, however, focusing on other environmentally sound options, such as the cultivation of protein-rich plants and the promotion of entomophagy, are more plausible options [39].

There are weak obligations on environmental assessment for exploratory fishes, as they often do not contain potential impacts on the whole ecosystem but only on target stocks. This approach lacks the assessment to consider the effects of non-target species such as associated habitats, food web, and the whole ecosystem [10]. In 1992, during a United Nations (UN) General Assembly, the problems related to harvesting fish from the ocean were addressed, with the result of the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (UNFSA). The agreement was enforced in 2001 with 83 participating parties and aims to ensure long-term sustainable conservation of fish stocks. The Conference furthermore agreed to participate in frequent performance reviews of Regional Fisheries Management Organizations (RFMOs) and develop best practice guidelines for doing performance reviews and implement the result, as well as promote participation in the agreement [40]. UNFSA lets the parties cooperate and govern via RFMOs. Those became the most preferred version in managing high sea fisheries but may not be efficient in the regulation of new mesopelagic fisheries, especially with regard to climate change challenges. Also, often, members do not follow the advice given by the RFMOs. There exists limited participation, consultation, and transparency.

Although there have been improvements in recent years, there is limited integration of biodiversity expressed and followed by fisheries management [10]. Beyond the regulations of national jurisdiction, there is still a severe portion of open water where there are no regulations to protect deep-sea fish. Human impact on marine life is recognized in treaties but mostly neglects negotiations for the management and conservation of mesopelagic fishes [11]. There are, however, possible options for strengthening the governance. Those include proactive engagement by RFMO members, such as exploring the potential impacts of fishing on the carbon cycle, committing to transparency, or participating in scientific bodies. Second, international guidelines could be developed as soon as there is more scientific knowledge to base those guidelines on. Third, a United Nations general assembly resolution giving the topic of mesopelagic fisheries more attention. Furthermore, there could be a high seas treaty in place with an internationally binding instrument to enforce environmental obligations and closer cooperation and help.

Another option would be, on the other hand, an agreement of states to refrain from deep-sea fisheries until scientific research is increased and, therefore, data and knowledge to provide appropriate management [10]. Some claim that deep-sea fisheries require highly precautionary catch limits and credible and time-constrained stock assessment advice. Sustainable management also needs to keep in mind that the ocean is a global ecosystem; fishing in one zone affects the other zones as well [41]. Large-scale exploitation of the deep sea should probably not begin, at least not until the severe gaps in information are accessed and incorporated into carefully considered management tools [32]. Others claim that it should be the other way around. While in the long term, mesopelagic fisheries may challenge biological, social, and economic sustainability, in the short term, policy instruments might be needed to stimulate the deep-sea fleet in order for it to successfully become a commercial fishery [33].

The central limitation of the study is that the findings of this review paper do not elaborate on the data-based scenarios of the exploitation of the fish biomass of the deep-seas. In addition to this, the presented paper has not proposed an applied model for a decision-support system for international organizations, such as FAO or Marine Stewardship Council. In the follow-up studies, the authors will try to analyze scenarios under different governance scenarios proposed in Chiambretto and Stahn [42]. Furthermore, the assessment of the strength of inferior incentives for the exploitation of deep-sea fish biomass should be assessed within a game theory framework proposed by Daniel Heyen [43] in the context of the governance and interaction patterns of global solar engineering.

6. Conclusions

The present review has demonstrated that fisheries have an important impact on the food security of the planet, and the future exploitation of mesopelagic fishes may contribute to that goal as well. Many people are suffering from hunger and malnutrition [6]. Fighting this is one of the key global policy goals today [4]. For this purpose, and as upper-level fishes are increasingly over-exploited, there has been increased interest in the opportunities of the mesopelagic zone as a new way to sustainably meet the needs of the increasing human population [24]. Exploiting the fishes living in the world´s oceans 200 to 1000 m below sea level may be linked to severe effects on the ecosystem and carbon sequestration [9].

Due to substantial knowledge gaps, international policies and governments may not be capable of efficiently managing these potential new kinds of commercial fisheries until further research is done [10]. However, there are close to two billion people suffering from deficiencies such as vitamin A, zinc, and iron. Seafood is one of the options to meet this need and, from a climate perspective, is preferable to pork or beef [6]. The link between fisheries and food security may be complex, as the availability of fish stocks may not intuitively lead to increased food security. People fish to contribute to their own and others’ food security directly but also draw income from trading fish for other food commodities, increasing food security indirectly [19]. Mesopelagic fish may provide more proteins than the rest of the biosphere [28].

These fish species are small, and this makes them particularly efficient for food consumption due to higher fertility rates per unit biomass than large fishes [18]. Glacier lanternfish and Mueller’s pearlside contain high levels of lipids and fatty acids, which are likely to be favored by consumers [31]. However, targeting new deep-water opportunities goes along with raising environmental and management concerns [25]. There are possibly several mechanisms linked between mesopelagic fishes and carbon cycling, which are not sufficiently studied yet [11]. In addition to the ecosystem services, potential by-catch stocks, food web interactions, and biodiversity need to be considered [31].

From a nutritious and food security perspective, the findings suggest large potential within different species of mesopelagic fishes. They contain large amounts of calcium and iodine. Fatty acids were also plenty and especially high in the lantern fish species. Iron and zinc levels were also found to be high [6]. Due to the knowledge gaps of the mesopelagic zone and the implications of potential commercial fisheries, there is a range of projects and initiatives set in motion to observe, monitor, and identify different aspects of the mesopelagic zone [10].

There are a few projects of the European Union that were funded within the European Union’s Horizon 2020 program. One of them is MEESO, which is coordinated by the Institute of Marine Research in Norway, running from 2019 to 2024 [37]. Another one is SUMMER, with the main goal of evaluating if and to what extent mesopelagic resources may be exploited without harming the essential ecosystem services that they provide [38]. In the last section of this paper, policy implications are shown. Harvesting from the mesopelagic ecosystem can indeed supply more food, but the potential consequences associated with the biomass extraction in climate regulation, conservation, biodiversity, and ecosystem stability have to be very well considered and call for a precautionary approach to protect mesopelagic fish species [32].

There is also a need for high-quality representative data on the different nutrient contents of mesopelagic fishes to predict nutrient profiles and draw information regarding policy recommendations from them. The different mesopelagic fish stocks may very well contribute to nutrient-dense food sources. However, the nutrient composition might vary [6]. It is clear that deep-sea fisheries have the potential to contribute to the food security of our planet, but due to the indicated knowledge gaps and the stated ecological impacts, more knowledge and further research are necessary.