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  • 1.
    Boonstra, Wiebren J.
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Oslo, Norway.
    Hentati-Sundberg, Jonas
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Classifying fishers' behaviour. An invitation to fishing styles2016In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 17, no 1, p. 78-100Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Brüchert, Volker
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sediment med nyckelroll i näringsväven2014In: HavsUtsikt, ISSN 1104-0513, Vol. 1, p. 20-21Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    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.

  • 3. Daewel, Ute
    et al.
    Hjøllo, Solfrid Saetre
    Huret, Martin
    Ji, Rubao
    Maar, Marie
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Travers-Trolet, Morgane
    Peck, Myron A.
    van de Wolfshaar, Karen E.
    Predation control of zooplankton dynamics: a review of observations and models2014In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 71, no 2, p. 254-271Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 4.
    Daw, Tim M.
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of East Anglia, United Kingdom.
    Coulthard, Sarah
    Cheung, William W. L.
    Brown, Katrina
    Abunge, Caroline
    Galafassi, Diego
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Peterson, Garry D.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    McClanahan, Tim R.
    Omukoto, Johnstone O.
    Munyi, Lydiah
    Evaluating taboo trade-offs in ecosystems services and human well-being2015In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 112, no 22, p. 6949-6954Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Drury O'Neill, Elizabeth
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Small-Scale Fisheries Governance: Broadening Perspectives on Markets, Relationships and Benefits in Seafood Trade2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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. 

  • 6.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Sydney, Australia.
    Byrne, Maria
    The sea cucumber fishery in Australia's Great Barrier Reef Marine Park follows global patterns of serial exploitation2015In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 16, no 2, p. 329-341Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Folkesson, Malin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Towards a Sustainable Fisheries Management: How to address uncertainty in order to achieve a sustainable development of regional fisheries management2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    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.

  • 8. Gephart, Jessica A.
    et al.
    Troell, Max
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Royal Swedish Academy of Sciences, Sweden.
    Henriksson, Patrik J. G.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. WorldFish, Penang, Malaysia.
    Beveridge, Malcolm C. M.
    Verdegem, Marc
    Metian, Marc
    Mateos, Lara D.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Deutsch, Lisa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    The 'seafood gap' in the food-water nexus literature-issues surrounding freshwater use in seafood production chains2017In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 110, p. 505-514Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Hansen, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Robertson-Andersson, Deborah
    Troell, Max
    Department of Systems Ecology.
    Control of the herbivorous gastropod Fissurella mutabilis (Sow.) in a land-based integrated abalone-seaweed culture2006In: Aquaculture, Vol. 255, no 1-4, p. 384-388Article in journal (Refereed)
  • 10.
    Hedberg, Nils
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sea cages, seaweeds and seascapes: Causes and consequences of spatial links between aquaculture and ecosystems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 11.
    Hedberg, Nils
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Stenson, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nitz Pettersson, Mika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Warshan, Denis
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nguyen-Kim, Hanh
    Tedengren, Michael
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kautsky, Nils
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Antibiotic use on Vietnamese fish and lobster sea cage farms and implications for the coral reef environment and human healthManuscript (preprint) (Other academic)
  • 12.
    Hedberg, Nils
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    von Schreeb, Kristina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Charisiadou, Stefania
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Jiddawi, Narriman
    Tedengren, Micael
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Mtwana Nordlund, Lina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Habitat preference for seaweed farming – a case study from Zanzibar, TanzaniaManuscript (preprint) (Other academic)
  • 13.
    Henricksson, Oskar
    et al.
    Södertörn University College.
    Mwandya, Augustine
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Population genetics structure of juvenile Mugil cephalus around Zanzibar and Bagamoyo (Tanzania) reveals multiple genetic demesManuscript (Other academic)
    Abstract [en]

    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.

  • 14.
    Hentati-Sundberg, Jonas
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Hjelm, J.
    Can fisheries management be quantified?2014In: Marine Policy, ISSN 0308-597X, E-ISSN 1872-9460, Vol. 48, p. 18-20Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    Hentati-Sundberg, Jonas
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Hjelm, J.
    Österblom, Henrik
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Does fisheries management incentivize non-compliance? Estimated misreporting in the Swedish Baltic Sea pelagic fishery based on commercial fishing effort2014In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 71, no 7, p. 1846-1853Article in journal (Refereed)
    Abstract [en]

    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. 

  • 16. Lu, Yu-Heng
    et al.
    Yagi, Nobuyuki
    Blasiak, Robert
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. The University of Tokyo, Japan.
    Factors contributing to effective management in the Sakuraebi (Sergia lucens) fishery of Donggang, Taiwan2017In: Marine Policy, ISSN 0308-597X, E-ISSN 1872-9460, Vol. 86, p. 72-81Article in journal (Refereed)
    Abstract [en]

    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.

  • 17.
    Metian, Marc
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Pouil, Simon
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Boustany, André
    Troell, Max
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Beijer Institute of Ecological Economics, Sweden.
    Farming of Bluefin Tuna-Reconsidering Global Estimates and Sustainability Concerns2014In: Reviews in Fisheries Science & Aquaculture, ISSN 2330-8249, Vol. 22, no 3, p. 184-192Article in journal (Refereed)
    Abstract [en]

    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.

  • 18.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Systems Ecology.
    Andersson, Mathias H.
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus D.
    Ian, Bryceson
    Spatial and seasonal variation of fish assemblages in mangrove creek systems in Zanzibar (Tanzania)2010In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 89, no 4, p. 277-286Article in journal (Refereed)
    Abstract [en]

    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.

  • 19.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Influence of mangrove deforestation on trophic organization of fish assemblages in creek systemsManuscript (Other academic)
    Abstract [en]

    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.

  • 20.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman, Marcus C
    Stockholm University, Faculty of Science, Department of Zoology.
    Andersson, Mathias H
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus
    Fisheries and Aquaculture.
    Fish assemblages in Tanzanian mangrove creek systems influenced by solar salt farm constructions2009In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 82, no 2, p. 193-200Article in journal (Refereed)
  • 21.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus
    Fisheries and Aquculture.
    Öhman, Marcus
    Stockholm University, Faculty of Science, Department of Zoology.
    Ian, Bryceson
    International Environment and Development Studies.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Distribution patterns of the striped mullet (Mugil cephalus) in mangrove creeks of Zanzibar, TanzaniaManuscript (Other academic)
    Abstract [en]

    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.

  • 22. Nielsen, Rasmus J.
    et al.
    Thunberg, Eric
    Holland, Daniel S.
    Schmidt, Jorn O.
    Fulton, Elizabeth A.
    Bastardie, Francois
    Punt, Andre E.
    Allen, Icarus
    Bartelings, Heleen
    Bertignac, Michel
    Bethke, Eckhard
    Bossier, Sieme
    Buckworth, Rick
    Carpenter, Griffin
    Christensen, Asbjorn
    Christensen, Villy
    Da-Rocha, José M.
    Deng, Roy
    Dichmont, Catherine
    Doering, Ralf
    Esteban, Aniol
    Fernandes, Jose A.
    Frost, Hans
    Garcia, Dorleta
    Gasche, Loic
    Gascuel, Didier
    Gourguet, Sophie
    Groeneveld, Rolf A.
    Guillén, Jordi
    Guyader, Olivier
    Hamon, Katell G.
    Hoff, Ayoe
    Horbowy, Jan
    Hutton, Trevor
    Lehuta, Sigrid
    Little, Richard L.
    Lleonart, Jordi
    Macher, Claire
    Mackinson, Steven
    Mahevas, Stephanie
    Marchal, Paul
    Mato-Amboage, Rosa
    Mapstone, Bruce
    Maynou, Francesc
    Merzéréaud, Mathieu
    Palacz, Artur
    Pascoe, Sean
    Paulrud, Anton
    Plaganyi, Eva
    Prellezo, Raul
    van Putten, Elizabeth I.
    Quaas, Martin
    Ravn-Jonsen, Lars
    Sanchez, Sonia
    Simons, Sarah
    Thébaud, Olivier
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ulrich, Clara
    van Dijk, Diana
    Vermard, Youen
    Voss, Rudi
    Waldo, Staffan
    Integrated ecological–economic fisheries models—Evaluation, review and challenges for implementation2018In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 19, no 1, p. 1-29Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 23. Purcell, Steven W.
    et al.
    Crona, Beatrice I.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. The Royal Swedish Academy of Sciences, Sweden.
    Lalavanua, Watisoni
    Eriksson, Hampus
    Distribution of economic returns in small-scale fisheries for international markets: A value-chain analysis2017In: Marine Policy, ISSN 0308-597X, E-ISSN 1872-9460, Vol. 86, p. 9-16Article in journal (Refereed)
    Abstract [en]

    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.

  • 24. Robertson-Andersson, Deborah V.
    et al.
    Potgieter, Michelle
    Hansen, Joakim
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Bolton, John J.
    Troell, Max
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Anderson, Robert J.
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Probyn, Trevor
    Integrated seaweed cultivation on an abalone farm in South Africa2008In: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 20, no 5, p. 579-595Article in journal (Refereed)
    Abstract [en]

    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.

  • 25.
    Tano, Stina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, A. S.
    Hailing, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tropical seaweed beds are important habitats for mobile invertebrate epifauna2016In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 183, p. 1-12Article in journal (Refereed)
    Abstract [en]

    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.

  • 26. Voss, Rudi
    et al.
    Quaas, Martin F.
    Stoeven, Max T.
    Schmidt, Jörn O.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Möllmann, Christian
    Ecological-Economic Fisheries Management Advice—Quantification of Potential Benefits for the Case of the Eastern Baltic COD Fishery2017In: Frontiers in Marine Science, ISSN 2296-2565, E-ISSN 1664-1078, Vol. 4, article id 209Article in journal (Refereed)
    Abstract [en]

    Fishing is a social and economic activity, and consequently socio-economic considerations are important for resource management. While this is acknowledged in the theory of Ecosystem-Based Management (EBM) and its sector-specific development Ecosystem-Based Fisheries Management (EBFM), currently applied fishery management objectives often ignore economic considerations. Year-to-year management, however, implicitly responds to short-term economic interests, and consequently, regularly resorts to tactical short-term rather than strategic long-term decisions. The aim of this article is to introduce a new way of estimating management advice referred to as an “ecologically-constrained Maximum Economic Yield” (eMEY) strategy, which takes into account ecological criteria as well as short- to medium-term economic costs. We further illustrate what net cost reductions per year are possible applying the eMEY strategy compared with the existing way of setting total allowable catches (TACs). The eMEY approach aims at maximizing the economic benefits for the fishery as well as society (consumers), while safeguarding precautionary stock sizes. Using an age-structured optimization model parameterized for the Eastern Baltic cod case study, we find that application of eMEY advice results in more stability in catch advice. Quantification and visualization of the costs of deviating from eMEY advice offers a transparent basis for evaluating decision-making outcomes. The costs of overfishing are mainly borne by the commercial fishery, while fishing less than optimal is particularly costly for the processing industry and consumers. To foster the uptake of our eMEY approach in current advice given by the International Council for the Exploration of the Sea (ICES) and the EU fishery management system, we suggest an easy-to-implement scheme of providing integrated advice, also accounting for economic considerations.

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