Fiskefria områden kan vara ett effektivt verktyg för att skydda både fisk- och kräftdjursbestånd och marina ekosystem. Men det är viktigt att områdena utformas på rätt sätt och är tillräckligt stora. Lektidsfredade områden kan vara enklare att driva igenom, men ger inte lika goda effekter.

The most recently revised CFP Regulation, adopted in 2013, includes a number of significant changes with the aim to make fisheries more in tune with concept of the ecosystem approach and to avoid unsustainable exploitation of marine biological resources, including fish, as a natural resource. As part of that the CFP Regulation introduced the landing obligation, an obligation to land all catches as opposed to previous praxis where fisheries have been relying on a system of discarding fish and other marine biological resources in order to optimize their catch. One aim with the landing obligation is to push for new adaptive fishing methods and in a way to implement an ecosystem approach since the fishing strategies are meant to be adjusted to ecosystem factors. To be effective, the system for controlling implementation must be adjusted to take different aspects of the ecosystem approach into account. The paper presents some reflections on the required balance between adaptive approaches connected to the ecosystem approach and the strictness established by principles of rule of law in relation to the so called EU CFP landing obligation. It is concluded that the best way to create a control system adjusted to these factors seems to be by giving more influence to the industry itself. Involving those concerned at all levels, and thus applying all aspects of the regulatory governance under an ecosystem approach, would create an effective adaptive system where the rule of law is also safe-guarded.

The study and classification of fishers’ behaviour remains a much debated topic. There is a tension between detailed empirical studies, which highlight the variety and diversity of fisheries, and the parsimony and generalization required to satisfy science and policy demands. This study contributes to this debate. The first sec- tion reviews quantitative methods currently used for classifying fishing practices. The review uncovers significant weaknesses in quantitative classification methods, which, we argue, can be improved through the complementary use of qualitative methods. To this purpose, we introduce the concept of ‘fishing style’, which integrates quantitative classification methods with qualitative analysis. We explain the scientific premises of the fishing-style concept, outline a general methodological framework and present a fishing-style analysis of Swedish Baltic Sea fisheries. Based on these results, we conclude that it is possible to classify fishing practices in a rel- atively uniform and limited number of styles that can highlight the rich, empirical diversity of fishers’ behaviour. We therefore propose that fishing-style analysis, based on an integration of quantitative and qualitative methods, can be an impor- tant step towards more effective and sustainable fisheries management.

I sedimenten sker processer som kan vara helt avgörande för näringsbalansen i havsvattnet. Omvandlingen av fosfor till olika former är relativt väl känd, medan detaljerna i kvävets kretslopp är betydligt mindre kända. Mer än hälften av den årliga tillförseln av kväve till Östersjön beräknas omsättas till kvävgas i sedimentet, vilket sedan går förlorat för de flesta marina organismer.

A circular economy is considered one way to reduce environmental impacts of human activities, by more efficient use of resources and recovery, resulting in less waste and emissions compared to linear take-make-dispose systems. Muscat et al. developed five ecological principles to guide biomass use towards a circular economy. A few studies have demonstrated environmental benefits of applying these principles to land-based food systems, but to date, these principles have not been explored in aquaculture. The current study expands on these principles and provides a narrative review to (i) translate them to aquaculture, while identifying implications for the main species and production systems, and (ii) identify the main pathways to make aquaculture more circular. We show that the underlying concepts of the ‘safeguard’, ‘entropy’, and ‘recycle’ principles have been well researched and sometimes well implemented. In contrast, the ‘avoid’ and ‘prioritise’ principles have been explored much less; doing so would provide an opportunity to decrease environmental impacts of aquaculture at the food-system level. One example is prioritising the production of species that contribute to food and nutrition security, have low environmental impacts and thinking at wider food system scale to avoid feed-food competition in aquaculture. We identified six priorities that could make aquaculture more circular: (i) increase production and demand for the most essential species, (ii) decrease food loss and waste at farm and post-harvest stages, (iii) support nutrient recycling practices at multiple scales, (iv) adapt aquafeed formulations, (v) inform consumers about benefits of species of low trophic levels and other environmentally friendly aquatic foods, and (vi) address urgent research gaps.

Blue foods, sourced in aquatic environments, are important for the economies, livelihoods, nutritional security and cultures of people in many nations. They are often nutrient rich1, generate lower emissions and impacts on land and water than many terrestrial meats2, and contribute to the health3, wellbeing and livelihoods of many rural communities4. The Blue Food Assessment recently evaluated nutritional, environmental, economic and justice dimensions of blue foods globally. Here we integrate these findings and translate them into four policy objectives to help realize the contributions that blue foods can make to national food systems around the world: ensuring supplies of critical nutrients, providing healthy alternatives to terrestrial meat, reducing dietary environmental footprints and safeguarding blue food contributions to nutrition, just economies and livelihoods under a changing climate. To account for how context-specific environmental, socio-economic and cultural aspects affect this contribution, we assess the relevance of each policy objective for individual countries, and examine associated co-benefits and trade-offs at national and international scales. We find that in many African and South American nations, facilitating consumption of culturally relevant blue food, especially among nutritionally vulnerable population segments, could address vitamin B₁₂ and omega-3 deficiencies. Meanwhile, in many global North nations, cardiovascular disease rates and large greenhouse gas footprints from ruminant meat intake could be lowered through moderate consumption of seafood with low environmental impact. The analytical framework we provide also identifies countries with high future risk, for whom climate adaptation of blue food systems will be particularly important. Overall the framework helps decision makers to assess the blue food policy objectives most relevant to their geographies, and to compare and contrast the benefits and trade-offs associated with pursuing these objectives.

We performed a literature review to examine to what degree the zooplankton dynamics in different regional marine ecosystems across the Atlantic Ocean is driven by predation mortality and how the latter is addressed in available modelling approaches. In general, we found that predation on zooplankton plays an important role in all the six considered ecosystems, but the impacts are differently strong and occur at different spatial and temporal scales. In ecosystems with extreme environmental conditions (e.g. low temperature, ice cover, large seasonal amplitudes) and low species diversity, the overall impact of top-down processes on zooplankton dynamics is stronger than for ecosystems having moderate environmental conditions and high species diversity. In those ecosystems, predation mortality was found to structure the zooplankton mainly on local spatial and seasonal time scales. Modelling methods used to parameterize zooplankton mortality range from simplified approaches with fixed mortality rates to complex coupled multispecies models. The applicability of a specific method depends on both the observed state of the ecosystem and the spatial and temporal scales considered. Modelling constraints such as parameter uncertainties and computational costs need to be balanced with the ecosystem-specific demand for a consistent, spatial-temporal dynamic implementation of predation mortality on the zooplankton compartment.

Managing ecosystems for multiple ecosystem services and balancing the well-being of diverse stakeholders involves different kinds of trade-offs. Often trade-offs involve noneconomic and difficult-to-evaluate values, such as cultural identity, employment, the well-being of poor people, or particular species or ecosystem structures. Although trade-offs need to be considered for successful environmental management, they are often overlooked in favor of win-wins. Management and policy decisions demand approaches that can explicitly acknowledge and evaluate diverse trade-offs. We identified a diversity of apparent trade-offs in a small-scale tropical fishery when ecological simulations were integrated with participatory assessments of social-ecological system structure and stakeholders' well-being. Despite an apparent win-win between conservation and profitability at the aggregate scale, food production, employment, and well-being of marginalized stakeholders were differentially influenced by management decisions leading to trade-offs. Some of these trade-offs were suggested to be taboo trade-offs between morally incommensurable values, such as between profits and the well-being of marginalized women. These were not previously recognized as management issues. Stakeholders explored and deliberated over trade-offs supported by an interactive toy model representing key system trade-offs, alongside qualitative narrative scenarios of the future. The concept of taboo trade-offs suggests that psychological bias and social sensitivity may exclude key issues from decision making, which can result in policies that are difficult to implement. Our participatory modeling and scenarios approach has the potential to increase awareness of such trade-offs, promote discussion of what is acceptable, and potentially identify and reduce obstacles to management compliance.

This licentiate adresses the relative ambiguity surounding benefit flows from small-scale fisheries seafood trade with a specific focus on how they may be impacted by market and social stuctures. Small-scale fishery governenace has previously taken a narrowly approach to sustainability. Focused on managing fishing activities, economic-led market interventions and overlooking the embededness of the fishers within a broader social structure. Also failing to address fisheries as interlinked social-ecological systems where feedbacks between the two can impact future sustainability. The larger PhD project takes a step towards combining these two out-of-focus areas by taking a systems perspective, through a Value Chain approach, to fisheries governance, associated market influences and the consequent benefit flows from marine ecosystem services. This licentiate begins by unpacking dynamics within the social realm that may impact benefit flows and ultimately resource extraction decisions, potentially contributing to feedbacks from the marine ecosystem. Research uses mixed-methods and is case-orientated with sites across two tropical marine small-scale fisheries in Zanzibar and the Philippines. Results present two market environments with distinct structures, conduct, reciprocity systems and notably, gender roles. However both systems experience economic transactions underlain by broader social relations and binds. These various features manifest themselves in different, yet often unexpected, ways through income equalities, distributions and reciprocal networks of fishers and trading actors. Once a broadened and diversified view of the SSF trading environment is appropriated, it is clear that benefit flows are impacted by various contextual features (e.g. gender, transaction forms and buyer types). Governance-related research or interventions should incorporate undervalued local attributes such as cultural characteristics, social relationships and market participation as they play a role in who benefits from seafood trade. Thus If governance is to be improved for sustainably increasing food and livelihood security it is necessary to unpack these benefit flow mechanisms and, in particular, the local social dynamics that mediate fishers’ everyday interplay with the marine ecosystem. Future steps include the aim to identify potential social-ecological feedbacks between the disentangled market environments and the local marine ecosystems as a result of interactions in SSF trade. 

This study assesses and identify major factors of social capital that affect the use of trade credit among shrimp farmers and how these contribute to and affect the profits of households in coastal provinces of the Mekong Delta, Vietnam. Data was collected through observations, informal discussions, and interviews with 364 shrimp farmers from the Ca Mau, Bac Lieu, Ben Tre and Tra Vinh provinces. The Probit and Tobit regression models were applied to analyze and evaluate the effect of social capital on the use of trade credit and the amount of trade credit used by farmers. The results show that many social capital factors affect the use of trade credit by shrimp farmers in the investigated areas, including in descending order of importance: profit, wholesale agents, colleague-friend-family line-neighbor, and trust. Besides the factors above, other factors such as agricultural land value, households’ income, distance, experiences in shrimp production, households’ assets, savings, profits of the previous crop, and the average household income had also an effect on trade use and amount of trade credit used by shrimp farming households. 

This study applied a stochastic frontier production model to analyze the technical (TE), allocative (AE), and economic (EE) efficiencies of intensive shrimp farming households, and to identify socioeconomic and shrimp farm-specific factors (farm size, labor, feed, seed, chemicals/medicine) that influence the TE, AE, and EE of shrimp production in the Ca Mau, Ben Tre, Bac Lieu, and Tra Vinh provinces of the Mekong Delta, Vietnam. The AE was calculated based on TE and EE. The stochastic frontier production and cost function model were used to evaluate the EE and TE at the shrimp farming household level. The results showed that the mean TE, AE, and EE of shrimp farming systems were 75%, 68.5%, and 61.4%, respectively. Age, gender, education, experience, cooperatives, and technical training significantly impacted the efficiency of shrimp production. The results suggest that shrimp farmers can improve shrimp productivity and EE by decreasing feed cost (FEE) and medicine/chemical cost (MED) of farm inputs. The study showed that shrimp farmers who participated in training activities, cooperatives, or management boards of aquaculture associations were more technically efficient than other farmers. The findings of this study provide essential information about the TE, AE, and EE of shrimp production, which can help local policy makers and shrimp farmers in the region to make better decisions on how to improve the EE and sustainability of shrimp production in the future. There is a need for recommendations on how to improve policies, technical guidance, and training courses on feed management and feeding practices, water quality, and disease management, to help shrimp farmers in the coastal provinces of the Mekong Delta to improve their shrimp production efficiencies in the future.

Tropical sea cucumber fisheries follow a predictable pattern of serial depletion. Overfishing is exacerbated in developing countries where management systems lack capacity to control large numbers of fishers influenced by poverty. In contrast, the tropical sea cucumber fishery in Australia's World Heritage listed Great Barrier Reef Marine Park (GBRMP) is operating in a developed high-income country with relatively few licensed fishers to manage. The development of this fishery is reviewed here in a meta-analysis of catches from 1991 to 2011. The fishery expanded to replace high-value teatfish species (Holothuria whitmaei and H.fuscogilva), fished heavily in initial stages of the fishery, with newly commercialized medium-value species such as burying blackfish (Actinopyga spinea) and curryfish (Stichopus herrmanni). These two species now constitute 80% of total catch. The annual average catch of burying blackfish was 208tonnes years 2004-11 and curryfish catches increased rapidly at an average annual pace of 200% from 2007-11. This serial harvest pattern occurred in the absence of baseline studies and without independent resource assessments, information required to inform relevant harvest predictions and to determine fishery impacts. This situation does not support ecologically relevant and adaptive decision-making in management and the unfolding catch patterns in the GBRMP follow those in low-income developing countries. The missing knowledge and lack of data serve as arguments to support precautionary reductions in harvests and extending fallow periods in fishing zones.

Fisheries management is not only about managing the resource fish, but also includes managing the social system. Aquatic ecosystems and the social system are both complex and change continuously. It is important to address what types of uncertainty the combination of both systems, complex socio-ecological systems leads to, their consequences and how these should be dealt with. Successful or unsuccessful management outcomes are difficult to address whether or not they are due to management efforts or natural changes. In addition, uncertainties often lead to a short-term management, since lack of knowledge makes it difficult to act in a long-term perspective. This thesis conceptualizes how to address different types of uncertainty prevalent in fisheries management, with focus on natural process uncertainty, measurement and estimation uncertainty, decision and implementation uncertainty, and institutional and regime uncertainty.  This was done by analyzing how three theoretical approaches, namely co-management, adaptive management and adaptive co-management address these uncertainties. In order to highlight how different types of uncertainty have been dealt with in practice, a case study on the fishery management in Lake Vättern has been made.

A comparison between the literature study and this thesis’ case study shows that hypothesis-testing, cooperation, communication and transparency are corresponding factors on how to deal with uncertainties in fisheries management and that institutional and regime uncertainty is inadequately addressed in Sweden.

Freshwater use for food production is projected to increase substantially in the coming decades with population growth, changing demographics, and shifting diets. Ensuring joint food-water security has prompted efforts to quantify freshwater use for different food products and production methods. However, few analyses quantify freshwater use for seafood production, and those that do use inconsistent water accounting. This inhibits water use comparisons among seafood products or between seafood and agricultural/livestock products. This 'seafood gap' in the food-water nexus literature will become increasingly problematic as seafood consumption is growing globally and aquaculture is one of the fastest growing animal food sectors in the world. Therefore, the present study 1) reviews freshwater use concepts as they relate to seafood production; 2) provides three cases to highlight the particular water use concerns for aquaculture, and; 3) outlines future directions to integrate seafood into the broader food-water nexus discussion. By revisiting water use concepts through a focus on seafood production systems, we highlight the key water use processes that should be considered for seafood production and offer a fresh perspective on the analysis of freshwater use in food systems more broadly. This is an open access article under the CC BY-NC-ND license.

Small-scale fisheries’ actors increasingly face new challenges, including climate driven shifts in marine resource distribution and productivity. Diversification of target species and fishing locations is a key mechanism to adapt to such changes and maintain fisheries livelihoods. Here we explore environmental and institutional factors mediating how patterns of spatial diversification (i.e., utilization of alternative fishing grounds) and target species diversification change over time. Using small-scale fisheries in Baja California Sur (Mexico) as a case study, we adopt a social-ecological network approach to conduct a spatially explicit analysis of fisheries landings data (2008–2016). This approach quantifies relative patterns of diversification, and when combined with a qualitative analysis of existing literature, enables us to illuminate institutional and environmental factors that may influence diversification strategies. Our results indicate that interannual changes in spatial diversification are correlated with regional oceanographic change, while illustrating the heterogeneity and dynamism of diversification strategies. Rather than acting in isolation, we hypothesize that environmental drivers likely operate in combination with existing fisheries regulations and local socioeconomic context to mediate spatial diversification. We argue that small-scale fisheries policies need to better account such linkages as we move towards an increasingly variable environment. Overall, our results highlight spatial diversification as a dynamic process and constitute an important step towards understanding and managing the complex mechanisms through which environmental changes affect small-scale fisheries.

Aquaculture is of growing importance in the global seafood production. The environmental impact of aquaculture will largely depend on the type of environment in which the aquaculture system is placed. Sometimes, due to the abiotic or biotic conditions of the seascape, certain aquaculture systems tend to be placed within or near specific ecosystems, a phenomenon that in this thesis is referred to as aquaculture system - ecosystem links. The exposed ecosystems can be more or less sensitive to the system specific impacts. Some links are known to be widespread and especially hazardous for the subjected ecosystem such as the one between the shrimp aquaculture and the mangrove forest ecosystem. The aim of this thesis was to identify and investigate causes and consequences of other spatial links between aquaculture and ecosystems in the tropical seascape.

Two different aquaculture system - ecosystem links were identified by using high resolution satellite maps and coastal habitat maps; the link between sea cage aquaculture and coral reefs, and the one between seaweed farms and seagrass beds. This was followed by interviews with the sea cage- and seaweed farmers to find the drivers behind the farm site selection. Many seaweed farmers actively choose to establish their farms on sea grass beds but sea cage farmers did not consider coral reefs when choosing location for their farms. The investigated environmental consequences of the spatial link between sea cage aquaculture and coral reefs were considerable both on the local coral reef structure, and coral associated bacterial community. Furthermore, coral reef associated fish are used as seedlings and feed on the farms, which likely alter the coral food web and lower the ecosystem resilience. Unregulated use of last resort antibiotics in both fish- and lobster farms were also found to be a wide spread practice within the sea cage aquaculture system, suggesting a high risk for development of antibiotic resistant bacteria. The effects of seaweed farms on seagrass beds were not studied in this thesis but have earlier been shown to be rather substantial within the borders of the farm but less so outside the farm.

Further, a nomenclature is presented to facilitate the discussion about production system - ecosystem links, which may also be used to be able to incorporate the landscape level within eco-certifying schemes or environmental risk assessments. Finally - increased awareness of the mechanisms that link specific aquaculture to specific habitats, would improve management practices and increase sustainability of an important and still growing food producing sector - the marine aquaculture.

Several papers have reported on the development of antibiotic resistance and implications for human medicine but fewer deal with environmental impacts of antibiotic use. Marine sea cage aquaculture in SE Asia is often established close to coral reef ecosystems. Large amounts of antibiotics are used in the cultivation of fish and lobster and hence released directly into the environment. This study investigates the antibiotic practices in sea cage farms producing fish and spiny lobster in Vietnam, mainly for the domestic market. There are approximately 3500 sea cage farms in Vietnam and we performed semi-structured interviews with 109 sea cage farmers asking them if they use antibiotics and if so; what sort/when/how often/how much. We found that the Vietnamese cage farmers are using antibiotics in an unstructured way, which seems to have little or no effect on the survival of the stock, or profit of the farm. The fact that the farmers live at their farm and use the sea next to the cages both for fishing and collecting filter-feeding bivalves for direct consumption, as well as a toilet, poses an additional risk for the spreading of human antibiotic resistant pathogens. Thirteen different antibiotics were found in the study. Eighty-two percentage of the lobster farmers and 28% of the fishfarmers used antibiotics. The average amounts used were over 5 kg per produced ton of lobster and about 0.6 kg per ton of fish, which is much higher than in other studies. Several antibiotic substances listed as critical and highly important for human medicine by WHO were used prophylactically and routinely with little control and enforcement of regulations. We tested and detected antibiotic resistance to Tetracycline, Vancomycin and Rifampicin in the coral associated bacteria Bacillus niabensis as far as 660m from fish farms with resistance decreasing with distance from the cage farms. The antibiotics are likely to have negative effects on the coral-symbiont relationship adding further risks to an already stressed environment.

There is a growing demand for wild caught juvenile fish to supply the market for aquaculture. However, little is known about the genetic effects of juvenile collection from wild populations. There are a number of imminent threats to both aquaculture systems and wild populations. Juvenile collection from a single population can for example reduce population’s evolutionary potential as well as the disease resistance within an aquaculture pond. In this study, we investigated the local genetic structure of juvenile Mugil cephalus collected from six sites around Bagamoyo (Tanzanian mainland) and Zanzibar Island, East Africa. Fish were caught in low tide using a seine net. All fish collected were juveniles with a total length ranging between 7 and 14 cm (mean length of about 10 cm). Samples were analyzed using Amplified Fragment Length Polymorphism (AFLP), and the Bayesian assignment test implemented in the STRUCTURE 2.2 software was applied to detect if sites were composed of several genetic demes. Our results indicate that all sites contain several different genetic demes suggesting that juvenile collection from a single site may neither harm the genetic diversity of wild M. cephalus nor reduce its disease resistance within an aquaculture system. By collecting juvenile fish from a single site one will in effect harvest juveniles from several genetic lineages.

Policy efforts to reduce fisheries impact have often created micro-management. Detailed regulations are restricting the fishing industry, and are also acknowledged to limit the progress towards sustainable management. Industry representatives, political bodies and scientists have therefore argued for more simplicity and transparency. Here, fisheries management is quantified in terms of trends in regulations for different Swedish fisheries in the Baltic Sea during the period 1995–2009. The results suggest that many fisheries are suffering from increased micro-management, but interestingly some fisheries showing a different trend.

Fisheries management agencies and fishing industry representatives depend on reliable estimates of fish biomass and mortality for the determin- ation of sustainable catch levels. Lack of data or misreporting may be reasons for unreliable stock assessment, which, in turn, may result in advice that does not reflect the availability of fisheries resources. It has been suggested that the mixed pelagic trawl fisheries in the Baltic represent a case of biased estimates of fish biomass and mortality resulting from misreporting. Here, we estimate the degree of misreporting in the Swedish pelagic fishery (1996 – 2009) and propose an approach for reconstructing historical catches based on commercial effort data. The analysis suggests that total catches have been underestimated during part of our study period and that systematic misreporting of species composition has taken place over the whole study period. The analysis also suggests that there is overcapacity in the fishery and that such economic incentive could explain the general patterns of misreporting. Applying our method for fisheries with suspected misreporting could significantly improve assessment accuracy, reduce uncertainty and thereby allow for a better link between catches and resource levels. 

This study analyzed the levels of heavy metals bioaccumulation in commonly consumed riverine fish species, including G. cavia, T. macrolepis, G. gotyla, S. plagiostomus, and M. armatus from River Swat in Pakistan, and quantify their potential risk to children and adults in general and fisherfolk communities using multiple pollution and risk assessment approaches. The highest metal detected by inductive coupled plasma mass spectrometry (ICP-MS) was Zn, which ranged from 49.61 to 116.83 mg/kg, followed by Fe (19.25–101.33 mg/kg) > Mn (5.25–40.35 mg/kg) > Cr (3.05–14.59 mg/kg) > Ni (4.26–11.80 mg/kg) > Al (1.59–12.25 mg/kg) > Cu (1.24–8.59 mg/kg) > Pb (0.29–1.95 mg/kg) > Co (0.08–0.46 mg/kg) > Cd (0.01–0.29 mg/kg), demonstrating consistent fluctuation with the safe recommendations of global regulatory bodies. The average bioaccumulation factor (BAF) values in the examined fish species were high (BAF > 5000) for Pb, Zn, Mn, Cu, Cr, Ni, and Cd, bioaccumulate (1000 > BAF < 5000) for Co, and probable accumulative (BAF <1000) for Fe, and Al, while the overall ∑heavy metals pollution index (MPI) values were greater than one (MPI > 1) indicating sever heavy metals toxicity in G. cavia, followed by S. plagiostomus, M. armatus, G. gotyla, and T. macrolepis. The multivariate Pearson's correlation analysis identified the correlation coefficients between heavy metal pairs (Ni Cr, Cu Cr, Pb Cr, Al Co, Cu Ni, and Pb Ni), the hierarchical cluster analysis (CA) determined the origin by categorizing heavy metal accumulation into Cluster-A, Cluster-B, and Cluster-C, and the principal component analysis (PCA) discerned nearby weathering, mining, industrial, municipal, and agricultural activities as the potential sources of heavy metals bioaccumulation in riverine fish. As per human risk perspective, S. plagiostomus contributed significantly to the estimated daily intake (EDI) of heavy metals, followed by G.cavia > M. armatus > G. gotyla > T. macrolepis in dependent children and adults of the fisherfolk followed by the general population. The non-carcinogenic target hazard quotient (THQ) and hazard index (HI) values for heavy metal intake through fish exposure were < 1, while the carcinogenic risk (CR) for individual metal intake and the total carcinogenic risk (TCR) for cumulative Cr, Cd, and Pb intake were within the risk threshold of 10⁻⁶–10⁻⁴, suggesting an acceptable to high non-carcinogenic and carcinogenic risk for both children and adults in the fisherfolk, followed by the general population.

An in-depth assessment was conducted on the functioning of a Taiwanese Sakuraebi (Sergia lucens) fishery management institution to understand the role of leadership in the context of long-term incentive creation. Interviews with relevant stakeholders and statistical analysis of fisheries data indicated that the daily vessel quota system and fishers' collective efforts to influence the market resulted in increased sales value, while simultaneously allowing for the equitable distribution of benefits from the Sakuraebi fishery in Donggang, Taiwan. Local fishers expressed a high level of satisfaction with the corresponding activities initiated by the fisher's organization. Interview respondents felt that promotional marketing activities led by the organization to enhance domestic consumption were particularly effective, and statistical analysis suggests that these activities helped to reduce the dependency of Taiwanese Sakuraebi fishers on export markets. A notable characteristic of this fishery is that it combines a large-scale sales organization, which enables the exertion of market influence, with a small-sized subsidiary organization for fisheries management. An annually rotating leadership system for managing fishery operations also provides members with the opportunity to share a sense of participation and responsibility, while keeping long-term policy goals. This study reinforces previous findings that leadership, social cohesion, and the nature of the resource are key factors determining the effectiveness and success of fisheries management.

Increased global demand for bluefin tuna has triggered unsustainable fishing and many wild stocks have seen dramatic declines. Improved fisheries governance is now slowly stabilizing many stocks and recently bluefin aquaculture has emerged as an economic alternative route for supplying the market. Most of captured bluefin tuna directly enters the global seafood market, but an increasing part of catches are destined to aquaculture (17-37%) as bluefin aquaculture almost exclusively depends on wild specimens for stocking. Farming is mainly being performed in the Mediterranean region, Mexico, Australia, and Japan. Few studies have focused on the global importance and future role of bluefin aquaculture and there are confounding uncertainties related to production volumes and trends. This study provides an overview of global bluefin tuna aquaculture and identifies its direct and indirect interactions with wild fish stocks, outlines some of the challenges for future expansion as well as pointing out significant mismatch of production statistics.

An investigative field survey was performed to gather baseline data on locally available feed ingredients and fish farming practices in different regions of Tanzania. More than 80% of respondents relied on locally available feed ingredients as a major feed supplement for their cultured fish, with maize bran being the most commonly used feed ingredient in all regions. Crude protein content in most analyzed local feed ingredients was medium-high, while crude fat content was high in some animal and agricultural by-products, and medium-low in other ingredients. Most respondents were males and the majority of fish farms were owned by individuals. Earthen pond was the most common fish farming system in all regions except Dar es Salaam. Semi-intensively mixed-sex tilapia monoculture was the dominating fish farming practice. The results of the survey presented provide a good platform for future development of culture systems and feeding strategies for tilapia in Tanzania.

Aquaculture production in Tanzania has increased in recent years, responding to an increased demand for fish, partly because of an increasing population and declining catches of wild fish. However, the current aquaculture production is still low, dominated by small scale farming systems, that are struggling with a number of challenges such as lack of improved fish breeds, feeds, technical skills and low adoption rates.

This thesis aims to assess the status of fish pond farming with a focus on integrated agriculture and aquaculture (IAA) systems in Tanzania, and to provide guidance on how these systems could be further developed to help local farmers to diversify their food production and income generation.

Methodologies included field observations, interviews, structured questionnaires, field experiments and laboratory analyses. Two field surveys in six districts and seven regions of Tanzania provided insights on the current status and the contribution of small-scale pond farming and IAA to household income and food production. Differences between IAA and non-IAA fish farming practices, and their influence on farm productivity and profitability were assessed. Also, opportunities, constraints and farmers’ future plans for fish farming were explored. Two field experiments were conducted on selected IAA systems identified during the surveys. One assessed the effect of including amaranth (Amaranthus hybridus) waste in locally produced fish feed on the yield of Nile tilapia (Oreochromis niloticus). Another investigated how the combination of different vegetables (A. hybridus and Brassica rapa pekinensis) and stocking densities of O. niloticus affected the water use efficiency, need for synthetic fertilizers and overall farm productivity and profitability.

The results show that small scale fish farming contributed with 13% of the farmers’ income. 38% of the fish was used for consumption and the remaining part was sold, contributing to both food security and livelihood diversification. Integration of tilapia and vegetables was the most common type of IAA system applied. Local feed ingredients contained medium to high content of crude protein, with high fat content in some animal by-products. The fish yield from the IAA ponds was 60% higher compared to non-IAA ponds because of a more frequent use of on-farm resources and better management. The net income from IAA ponds was 175% higher compared to non-IAA ponds, due to reduced costs and higher yields. Major constraints included water problems, lack of technical skills and good quality fish seeds and feeds. Overall, fish farmers had a positive attitude towards fish farming and the majority were willing to continue with fish farming, with IAA farmers being more positive than non-IAA farmers. The use of amaranth wastes as a fish feed ingredient in a tilapia-amaranth integrated system did not affect the fish growth and yield, but rather improved the feed conversion ratio. The multiple use of water in integrated tilapia-vegetable systems increased the water use efficiency and reduced the need for synthetic fertilizers. Although water from high fish stocking densities increased the vegetable yield, the overall farm productivity in the IAA system was negatively affected because of low fish growth and survival rates. Since agriculture is already popular and fish farming is expanding, promotion of IAA systems could provide an entry point for an increased adoption of aquaculture among rural farmers.

Organic wastes can be recycled in an ecologically sound way in fishponds by applying integrated agriculture and aquaculture systems (IAA). This kind of waste recycling can help to protect the environment from pollution and improve fishpond yields. Additionally, IAA provides an opportunity for diversification of the output from two or more existing subsystems leading to higher overall farm economic returns. This study explored the potential application of amaranth wastes (AW) as a dietary ingredient for tilapia in a tilapia-amaranths integrated system (ITA). An experimental diet (AD) contained 10% (based on the control diet, CD) inclusion of AW collected from a nearby vegetable market. The experiments included triplicate treatments with; (i) fish fed on AD, where the pond water was used for irrigating the amaranth plants (IAA-fish), and (ii) fish fed on CD, where no pond water was used for irrigating the amaranth plants (non-IAA fish). 90 days after fish stocking, eighteen 4 m2 amaranth plots were prepared and treated with (i) tap water without fertilization (control amaranths), (ii) water from IAA-fish pond and organically fertilized (IAA amaranths), and (iii) tap water and inorganically fertilized (non-IAA amaranths). The use of AW improved the fish feed conversion ratio. The overall net income from ITA was 3.2, 2.3, 2.6, and 1.8 higher than from non-IAA amaranths, IAA-amaranths, non-IAA fish, and IAA fish sub-systems respectively.

Spatial and seasonal variations of fish assemblage composition were studied in three non-estuarine mangrove creeks of Zanzibar (Tanzania). Fish were collected monthly for one year at three sites (lower, intermediate and upper reaches) in each creek using a seine net (each haul covering 170 m(2)). Density, species number and diversity of fish were all higher at sites with dense cover of macrophytes (seagrass and macroalgae) than over unvegetated sandy sites. In general, fish assemblages mainly comprised juveniles of a few abundant taxa, e.g. Mugil cephalus, Mugilidae spp. and Leiognathus equulus at sites with mud substratum and Germs oyena, Lethrinus harak and Sillago sihama at sites dominated by macrophytes. Multivariate analyses revealed significant separations in fish assemblage composition within the two creeks where the bottom substratum differed among sites. Overall, season seemed to have little effect on density, species number, diversity index (H') and assemblage structure of fish. Water condition variables were also relatively stable across the season, although a short-term fluctuation primarily induced by decreased salinity, occurred during the heavy rains in April and May. Fish assemblage structure was not significantly affected by any of the abiotic factors tested. However, significant regressions were found between the other fish variables and environmental variables, but since these associations were mostly species-specific and generally inconsistent, we suggest that the overall distribution patterns of fish were mainly an effect of particular substrate preferences of fish species rather than contemporary water conditions.

The mangrove biotopes in Tanzania are under increasing pressure from domestic uses and changes in land-use for aquaculture and solar salt farms. To investigate the impacts of man-made activities on trophic structure of mangrove-associated fish species, sampling of fish from various trophic groups was performed in mangrove creeks. Trophic organization and stable isotope signatures (δ ¹³C and δ ¹⁵N) of fish in undisturbed areas of mangrove creeks were compared with clear-cut areas of mangrove as well as with reservoirs for saltworks or fish farms constructed after mangrove clearing. Results showed significantly higher densities, species numbers, diversity (H’) and numbers of trophic groups in undisturbed sites compared to both types of disturbed sites. Overall, omnivorous fish comprised the most abundant feeding guild, with the highest number of individuals found in the cleared sites followed in order by the uncleared sites and the reservoirs. The feeding guild zoobenthivores/piscivores was the most diverse group, with the highest species richness in the undisturbed areas. Multivariate analysis showed that assemblage structure of omnivores in the reservoirs was separated from those in the uncleared and cleared sites, while zoobenthivores/piscivores differed between uncleared sites and the disturbed areas (cleared sites and reservoirs). Stable isotope ratios of δ¹³C and δ¹⁵N values in fish tissue muscles indicate significant diet shifts between undisturbed and disturbed mangrove creek systems, although the effects are species-specific. Our findings suggest that mangrove deforestation combined with land-use changes, such as salt- or fish farm constructions, has a greater impact on the trophic structure of fish in mangrove creeks than mangrove deforestation only. Hence, the extent and severity of disturbance seem to be important in predicting fish assemblage composition.

Spatial and seasonal variations in density of the striped mullet Mugil cephalus were investigated in four mangrove creeks in Zanzibar (Tanzania) during a one-year cycle. Fish were collected monthly in the lower, intermediate and upper reaches of each creek using a beach seine net (each haul covering 170 m²). All individuals collected were juveniles with a mean size of 2 to 16 cm (standard length). The density of juvenile mullets inhabiting mangrove creeks differed significantly among the different creeks, but the patterns within creeks were consistent, with higher densities upstream in three of the creeks. In general, small-sized juvenile mullets (2-10 cm) were more abundant in the upper reaches compared to the lower and intermediate sites in most creeks. Seasonal patterns were fairly weak, although high mullet densities were observed during the period of heavy rains (from March to May). Principal component analysis (PCA) showed that a muddy bottom with microphytobenthos was likely important to explain high mullet densities, although site-specific variables like low water depth and water clarity may also be important. Our findings suggest that the densities of juvenile striped mullet vary among sites and creeks in response to refuge availability from turbid shallow waters and the accessibility of food resources from benthic microalgae.

Marine ecosystems evolve under many interconnected and area-specific pressures. To fulfil society's intensifying and diversifying needs while ensuring ecologically sustainable development, more effective marine spatial planning and broader-scope management of marine resources is necessary. Integrated ecological–economic fisheries models (IEEFMs) of marine systems are needed to evaluate impacts and sustainability of potential management actions and understand, and anticipate ecological, economic and social dynamics at a range of scales from local to national and regional. To make these models most effective, it is important to determine how model characteristics and methods of communicating results influence the model implementation, the nature of the advice that can be provided and the impact on decisions taken by managers. This article presents a global review and comparative evaluation of 35 IEEFMs applied to marine fisheries and marine ecosystem resources to identify the characteristics that determine their usefulness, effectiveness and implementation. The focus is on fully integrated models that allow for feedbacks between ecological and human processes although not all the models reviewed achieve that. Modellers must invest more time to make models user friendly and to participate in management fora where models and model results can be explained and discussed. Such involvement is beneficial to all parties, leading to improvement of models and more effective implementation of advice, but demands substantial resources which must be built into the governance process. It takes time to develop effective processes for using IEEFMs requiring a long-term commitment to integrating multidisciplinary modelling advice into management decision-making.

Aquaculture is a crucial sector for Egyptian food production, providing a cheap source of animal protein while securing income and employment for a substantial part Egypt's population. Nile tilapia (Oreochromis niloticus) is the most commonly produced fish, usually farmed in earthen ponds around the Northern Delta Lakes. A common practice among farms is to fertilize ponds with chicken manure (CM) in order to increase nutrient levels and promote phytoplankton, consumed by the fish. However, with reports of use of antibiotics in Egypt's poultry sector, and that CM contains residues of antibiotics, antibiotic resistant pathogens and antibiotic resistance genes (ARGs) are production benefits large enough to compensate a potential health hazard?

Using production data from 501 aquaculture farms and fish pond sediment from 28 ponds we evaluated potential benefits in yields and profitability for farms using CM for fertilization, and used qPCRs to screen sediments for three antibiotic resistance genes coding for resistance to the most commonly used antibiotics in the poultry sector. The analysis showed no significant benefits to fish yields or profitability in farms where CM was applied, but a risk of significantly increased nutrient loads. Meanwhile, we detected increased abundances of tetA and tetW resistance genes in fish pond sediment where CM was applied. With the risk of disseminating ARGs and causing eutrophication of local waterways, we recommend that Egyptian tilapia pond farmers refrain from using CM and adopt best management practices for increasing farm profitability in order to to reduce environmental and health hazards.

A greater focus on governance is needed to facilitate effective and substantive progress toward sustainability transformations in the aquaculture sector. Concerted governance efforts can help move the sector beyond fragmented technical questions associated with intensification and expansion, social and environmental impacts, and toward system-based approaches that address interconnected sustainability issues. Through a review and expert-elicitation process, we identify five engagement arenas to advance a governance agenda for aquaculture sustainability transformation: (1) setting sustainability transformation goals, (2) cross-sectoral linkages, (3) land–water–sea connectivity, (4) knowledge and innovation, and (5) value chains. We then outline the roles different actors and modes of governance can play in fostering sustainability transformations, and discuss action items for researchers, practitioners, and policymakers to operationalize activities within their engagement arenas.

Millions of people around the world depend on the ecosystem services produced by rocky and coral reef ecosystems, including nutrition, aesthetic value, and coastal protection. Rocky and coral reefs also contribute to critical global and regional processes through the cycling of nitrogen, phosphorus, and carbon. The increased stress experienced by reefs in the Anthropocene threatens their ability to provide vital ecosystem services. This study investigates bundles of ecosystem services, ecosystem services that occur together, to identify trade-offs and synergies among services produced by coral reefs. To do this, we bring together estimates of seven ecosystem services: productivity, nitrogen cycling, phosphorus cycling, inorganic carbon cycling, aesthetic value, nutritional value, and coastal protection. We use correlations analysis to understand trade-offs and synergies between these seven ecosystem services and cluster analysis to identify clusters of reefs with distinct suites of ecosystem services, or ecosystem service bundles. Our analysis reveals (1) synergies and trade-offs among the seven ecosystem services, and (2) three distinct clusters of reefs, which differ on the basis of their overall and relative delivery of ecosystem services. Differences in service production among the clusters appear to be linked to differences in key ecological traits, including total reef fish biomass and species richness. Similar applications of ecosystem service bundles analysis in other marine and coastal systems could result in improved understanding of the spatial distributions and relationships between marine ecosystem services, which is a key input to marine policy.

Livelihood initiatives are common within marine protected areas (MPAs) aiming for poverty alleviation or higher income opportunities. However, results can be mixed in reality, as well as change over time. Furthermore, who benefits is a key consideration, as results can vary based on inequalities, including gender. Here, the monetary outcomes of different livelihood strategies were investigated across three MPA regions in Zanzibar, Tanzania. Using a quantitative approach, the results show that livelihoods have shifted in a six-year period, with livelihood strategies differing in poverty incidence and income. Livelihood initiatives, namely seaweed farming and tourism, did not provide significantly higher monetary returns compared to long-standing livelihoods, such as fisheries. Seaweed farming showed income stability but a high poverty incidence predominantly within women-headed households. During the study period, men primarily remained in fisheries, whilst women shifted to small-scale businesses and fisheries, largely exiting seaweed farming. This underscores a need for adaptive, gender sensitive management within fast changing coastal contexts.

Small-scale fishers are often believed to receive marginal earnings for seafood relative to other value-chain actors but proportionate incomes across different traded species are rarely compared. This study compares value chains for 15 species of sea cucumbers between Fiji and Kiribati using data collected on sale prices of dried products (beche-de-mer) from fishers to middlemen and exporters, export prices and market retail prices in China. Pacific islanders comprised almost all fishers, but represented only some middlemen and few exporters. Proportional increases in prices along the value chains differed greatly among sea cucumber species and between countries. Fishers' earnings varied greatly among species. The relative share of the end market value they received was negatively related to product end-market value; on average 50% of the end retail value for the lowest-value species but < 10% for the highest-value species. Most fishers lacked information about market prices. The gross markup of exporters differed greatly between the two countries. Downstream actors reaped increasingly higher proportions of the product value for higher value species. Variation in sale prices between countries and fishers for the same product indicates a potential for higher earnings to fishers. Improved transparency of prices to fishers could empower them to negotiate higher prices, especially for more valuable species. Upgrading of value-chain governance, e.g. through fisher cooperatives or auction systems, could improve efficiency and fisher incomes, potentially reducing the need for high fishing rates. Such interventions will benefit from understanding the value-chain patterns among different species harvested in multispecies fisheries.

Land-based abalone aquaculture in South Africa, based on the local species Haliotis midae, started in the early 1990s and has grown rapidly in the last decade, with 13 commercial farms now producing over 850 t per annum. Over 6,000 t per annum of kelp Ecklonia maxima are now harvested for this purpose, and some kelp beds are reaching maximum sustainable limits. Research into seaweed aquacultureas feed (Ulva and some Gracilaria) for abalone started in the late 1990s on the southeast coast (where thereare no kelp beds) using abalone waste water. A growing body of evidence suggests that a mixed diet of kelp plus other seaweeds can give growth rates at least as good ascompound feed, and can improve abalone quality and reduce parasite loads. A pilot scale Ulva lactuca and abalone integrated recirculation unit using 25% recirculation was designed and built on the south west coast of South Africa using one 12,000-L abalone tank containing 13,200 15±2.5 g abalone, connected to two 3,000-L seaweed tanks containing an initial starting biomass of 10 kg of seaweed, replicated 3 times. In an 18-month period, there were no significant differences in abalone health or growth rates, sediment build up and composition, mobile macro fauna densities and species between the recirculation or the flowthroug hunits. Transfer of oxygen generated by the seaweeds to the abalone tanks was poor, resulting in the recirculated abalone tanks having lower (33%) dissolved oxygen concentrations than a comparable flow-through abalone unit. Seaweed nutrient content and specific growth rates in the units were comparable to seaweeds cultivated in fertilized effluent (SGR=3.2±3.4%.day−1; Yield=0.2±0.19 kg.m2.day−1). Indications were that at this low recirculation ratio the seaweeds in the units were nutrient limited and that there were no negative effects to the abalone being cultivated insuch a recirculation unit at this recirculation ratio.

Seascape configuration is known to influence fish distribution and abundance in coastal waters. However, there is little information regarding how the shape of the coastal seascape influences catches of landed fisheries species, particularly so in the understudied western Indian Ocean (WIO). With focus on big blue octopus (Octopus cyanea), which is a widely found cephalopod species in the WIO, we compared landed catches (biomass, catch rate, and density) in submerged and exposed reefs, and explored the influence of proximity to fishing villages and reef habitat size on octopus landings. We used fishery-dependent data collected between 2018 and 2020 from eight landing sites spread across the Tanzanian coast. We found a strong relationship between biomass of octopus catch and distance from fished reefs to fishing villages, with higher fished biomass on reefs farther away. Octopus densities were higher, while catch rates were lower, on reefs very close to (within one km distance from) fishing villages compared to more distant reefs. In general, submerged reefs provided higher catches than exposed reefs. The low octopus catches on the exposed reefs were attributed to high fishing pressure, while submerged reefs that are only accessible through diving provide optimal areas for octopuses to grow. Octopus catches were, however, not significantly affected by reef size. The findings suggest that management policies should proportionate fishing efforts to ensure sustainable exploitation of reefs and associated fishery resources.

Fishers, scientists and policy makers need to describe, understand and “agree on” variations in fish catches caused by exploitation and climate change for effective fisheries management. To achieve this, relevant data with sufficient spatiotemporal resolution is a necessity. In regions of the Global South, such as the Western Indian Ocean (WIO), fish catch data useful for management is scarce or non-existing. Still, the potential of local ecological knowledge to provide such information has not been fully utilised in these regions. In this study, we evaluated fishers’ local ecological knowledge (based on interviews) against detailed seasonal fish catch variability data based on catch per unit effort (CPUE) records. Because of the importance of the monsoon seasons for marine resource variability, differences in fish catches during the northeast (NE) and southeast (SE) monsoon seasons were investigated. Fishers’ perceptions generally agreed with catch data records, both showing that the NE monsoon season generally provides higher catch rates than the SE monsoon season. The fishers’ perceptions at two of the landing sites (Nyamisati and Shangani) contradict the recorded observations by showing highest fish catches during the SE monsoon season. It was clear, however, that fishers’ perceptions in these two sites focused on the most valuable target species (prawn and tuna in Nyamisati and Shangani, respectively) rather than total catches. In this particular case, fishers’ perceptions facilitated the significance of taking target species into consideration. The findings of this study highlight the importance of integrating local ecological knowledge into scientific research to help understand the complex dynamics of coastal fisheries and improve the management of data-poor fisheries.

The global population is expected to increase and the greatest challenge for the world’s food-producing sector is to secure food and nutrition through sustainable production methods and reduced waste. Aquaculture is the cultivation of aquatic organisms including fish, molluscs, crustaceans and algae, and has a significant role in providing food and employment as the demand for food is increasing. In this study, conventional open-net pen farming was compared to semi-closed aquaculture systems (S-CCS), as well as the possibility of implementing integrated multi-trophic aquaculture (IMTA) in Sweden. Open-net pens are cost-effective and well-proven methods, but due to environmental impacts, the opportunities are limited. Cultivation in S-CCS reduces the environmental impact by strengthening the barrier between the cultivated organism and the surroundings. Implementing IMTA offers the potential for diversification of aquaculture production and economic yield. Sweden has major potential to develop competitive aquaculture through sustainable technological solutions and by diversifying productivity.

Marine salmon farming is a new and fast-growing industry in Iceland after decades of uncertainties within aquaculture development in the country. While growing at a tremendous speed in the last few years, the development has been challenged by different social groups in regard to its socio-economic and environmental effects. Research has shown that there is a lack of knowledge on the perceptions on different stakeholders involved in the farming. This study aims to investigate how different stakeholders perceive the marine salmon farming industry being established in Bíldudalur, in the Westfjords of Iceland, by conducting a case study. Semi structured interviews were carried out with different stakeholders as well as an online survey was distributed to the residents of Bíldudalur, following a focus groupdiscussion.

Analysis of the responses demonstrated that current aquaculture regulations have not held up with the expanding industry which has created tension amongst stakeholders. The results show that many worry about the wild salmon stock and that with current regulations, it is hard to predict how much marine farmed salmon will be bred in Iceland, due to weak regulations. Simultaneously, the local community of Bíldudalur has experienced a lot of positive changes in their rural community following the establishment of fish farming in their community.

On this basis, further research is needed to compare the findings to other rural communities involved in fish farming in Iceland as well as further research on Iceland´s current changes in regulation and policies and how aquaculture development is promoted in Iceland.

Marine macrophyte habitats in temperate regions provide productive habitats for numerous organisms, with their abundant and diverse invertebrate epifaunal assemblages constituting important linkages between benthic primary production and higher trophic levels. While it is commonly also recognized that certain vegetated habitats in the tropics, such as seagrass meadows, can harbour diverse epifaunal assemblages and may constitute important feeding grounds to fish, little is known about the epifaunal assemblages associated with tropical seaweed beds. We investigated the abundance, biomass and taxon richness of the mobile epifaunal community (>= 1 mm) of tropical East African seaweed beds, as well as the abundance of invertivorous fishes, and compared it with that of closely situated seagrass meadows, to establish the ecological role of seaweed beds as habitat for epifauna as well as potential feeding grounds for fish. The results showed that seaweed beds had a higher abundance of mobile epifauna (mean SD: 10,600 +/- 6000 vs 3700 +/- 2800 per m(2)) than seagrass meadows, as well as a higher invertebrate biomass (35.9 +/- 46.8 vs 1.9 +/- 2.1 g per m(2)) and taxon richness (32.7 +/- 11.8 vs 19.1 +/- 6.3 taxa per sample), despite having a lower macrophyte biomass. Additionally, the high abundance of invertivorous fishes found in seaweed beds indicates that they act as important feeding grounds to several fish species in the region.

Octopus cyanea (Gray, 1849), abundant in the South-West Indian Ocean (SWIO), constitutes a vital resource for both subsistence and commercial fisheries. However, despite this socioeconomic importance, and recent indications of overfishing, little is known about the population structure of O. cyanea in the region. To inform sustainable management strategies, this study assessed the spatio-temporal population structure and genetic variability of O. cyanea at 20 sites in the SWIO (Kenya, Tanzania, Mozambique, Madagascar, Mauritius, Rodrigues, and the Seychelle Islands) by complementary analysis of mitochondrial DNA (mtDNA) noncoding region (NCR) sequences and microsatellite markers. MtDNA analysis revealed a shallow phylogeny across the region, with demographic tests suggesting historic population fluctuations that could be linked to glacial cycles. Contrary to expectations, NCR variation was comparable to other mtDNA regions, indicating that the NCR is not a hypervariable region. Both nuclear and mtDNA marker types revealed a lack of genetic structure compatible with high gene flow throughout the region. As adults are sedentary, this gene flow likely reflects connectivity by paralarval dispersal. All samples reported heterozygote deficits, which, given the overall absence of structure, likely reflect ephemeral larval recruitment variability. Levels of mtDNA and nuclear variability were similar at all locations and congruent with those previously reported for harvested Octopodidae, implying resilience to genetic erosion by drift, providing current stock sizes are maintained. However, as O. cyanea stocks in the SWIO represent a single, highly connected population, fisheries may benefit from additional management measures, such as rotational closures aligned with paralarval ecology and spanning geopolitical boundaries. 

The diverse aquaculture sector makes important contributions toward achieving the Sustainable Development Goals (SDGs)/Agenda 2030, and can increasingly do so in the future. Its important role for food security, nutrition, livelihoods, economies, and cultures is not clearly visible in the Agenda 21 declaration. This may partly reflect the state of development of policies for aquaculture compared with its terrestrial counterpart, agriculture, and possibly also because aquaculture production has historically originated from a few key hotspot regions/countries. This review highlights the need for better integration of aquaculture in global food system dialogues. Unpacking aquaculture's diverse functions and generation of values at multiple spatiotemporal scales enables better understanding of aquaculture's present and future potential contribution to the SDGs. Aquaculture is a unique sector that encompasses all aquatic ecosystems (freshwater, brackish/estuarine, and marine) and is also tightly interconnected with terrestrial ecosystems through, for example, feed resources and other dependencies. Understanding environmental, social, and economic characteristics of the multifaceted nature of aquaculture provides for more context-specific solutions for addressing both opportunities and challenges for its future development. This review includes a rapid literature survey based on how aquaculture links to the specific SDG indicators. A conceptual framework is developed for communicating the importance of context specificity related to SDG outcomes from different types of aquaculture. The uniqueness of aquaculture's contributions compared with other food production systems are discussed, including understanding of species/systems diversity, the role of emerging aquaculture, and its interconnectedness with supporting systems. A selection of case studies is presented to illustrate: (1) the diversity of the aquaculture sector and what role this diversity can play for contributions to the SDGs, (2) examples of methodologies for identification of aquaculture's contribution to the SDGs, and (3) trade-offs between farming systems' contribution to meeting the SDGs. It becomes clear that decision-making around resource allocation and trade-offs between aquaculture and other aquatic resource users needs review of a wide range of established and emergent systems. The review ends by highlighting knowledge gaps and pathways for transformation that will allow further strengthening of aquaculture's role for contributing to the SDGs. This includes identification and building on already existing monitoring that can enable capturing SDG-relevant aquaculture statistics at a national level and discussion of how a cohesive and comprehensive aquaculture strategy, framed to meet the SDGs, may help countries to prioritize actions for improving well-being.

Finding ways to keep global warming under 1.5 degrees Celsius is urgent and will need a portfolio of solutions. Seaweeds are marine photosynthetic organisms that humans harvest either from the wild or farm, to be used in many applications and providing various ecosystem services. Large scale farming of seaweeds for absorbing carbon has lately been promoted as a climate “fix”. The major shortcomings of this argument relate to the idea that a carbon sink function should exist through carbon accumulation in seaweed biomass simultaneously as seaweeds are consumed as food by humans, fed to animals, or used in many alternative applications. This carbon instead enters the fast carbon cycle and does not provide any “carbon sink” function. Radical suggestions of intentionally transfer of farmed seaweeds to the deep-sea to accomplish a longer removal are highly questionable from feasibility, economic, ecosystem effects and ethical resource use perspectives. Development of “ocean forests” for carbon capturing through farming should not be compared to forests on land as these provide carbon removal from the atmosphere at sufficiently long time scales to be qualified as carbon sequestration - thus making a difference related to reducing atmospheric greenhouse gas concentrations. Seaweeds can, however, play a role in reducing greenhouse gas emissions from the overall food system through carbon offset - i.e. if replacing food, feed, and/or materials that have larger carbon footprints. The fate/cycling of carbon as particulate and dissolved matter from both farmed and wild seaweeds, are however not fully understood, especially with respect to pathways and time scales relevant for carbon removal/storage. Another potential pathway for their role in decarbonization may be through reducing enteric methane emissions from ruminants and also through bioenergy production. More research is, however, needed for understanding the contributions from such interventions. Presenting seaweed farming as a quick fix for the climate risks facilitating misdirected investments (for carbon abatement solutions) and reducing demand for specific research and technological development that will be needed for increasing our understanding about seaweeds’ contribution to food/feed systems and additional sustainability services and benefits.