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  • 1. Alexander, Karen A.
    et al.
    Heymans, Johanna J.
    Magill, Shona
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Holmes, Steven J.
    Wilding, Thomas A.
    Investigating the recent decline in gadoid stocks in the west of Scotland shelf ecosystem using a foodweb model2015In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 72, no 2, p. 436-449Article in journal (Refereed)
    Abstract [en]

    Abundance and biomass of cod, haddock, and whiting in the waters off of the west coast of Scotland (wcoS) have undergone large changes in recent years, most notably a recent decline. These three species contribute a considerable part of Scottish demersal landings from this area and as such it is important to understand why these stocks are behaving the way they are. A number of explanations for the decline have been proposed, including: seal predation, pressure from Nephrops trawls, and fishing pressure more generally. We used an ecosystem model of the wcoS continental shelf (<200 m depth) to investigate whether these proposed explanations for declining gadoid stocks are feasible. Results suggest that the rise in the grey seal population over recent years has not led to the decline in gadoid stocks; there is insufficient bycatch by the Nephrops fleet to have a large impact on gadoid stocks; however, fishing, as a key driver of the west of Scotland shelf ecosystem, has impacted stocks and by decreasing fishing levels to maximum sustainable yield cod biomass may increase slightly though not returning to previous levels. Although this means we are little further forward in understanding the cause of recent gadoid declines in the area, the development of this model has enabled us to further our knowledge and understanding of aspects of trophic structure and the impacts of fishing on the wcoS.

  • 2.
    Bauer, Barbara
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Meier, H. E. Markus
    Casini, Michele
    Hoff, Ayoe
    Margoński, Piotr
    Orio, Alessandro
    Saraiva, Sofia
    Steenbeek, Jeroen
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Reducing eutrophication increases spatial extent of communities supporting commercial fisheries: a model case study2018In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 75, no 4, p. 1306-1317Article in journal (Refereed)
    Abstract [en]

    In this study we investigate if eutrophication management has the potential to substantially affect which areas are going to be most suitable for commercial fishing in the future. We use a spatial ecosystem model, forced by a coupled physical-biogeochemical model, to simulate the spatial distribution of functional groups within a marine ecosystem, which depends on their respective tolerances to abiotic factors, trophic interactions, and fishing. We simulate the future long-term spatial developments of the community composition and their potential implications for fisheries under three different nutrient management scenarios and changing climate. The three nutrient management scenarios result in contrasting developments of bottom oxygen concentrations and phytoplankton abundance, with substantial effects on fish production. Nutrient load reduction increases the spatial extent of the areas suitable for the commercially most valuable demersal fish predator and all types of fisheries. This suggests that strategic planning of fishery management strategies could benefit from considering future changes in species distributions due to changes in eutrophication. We show that combining approaches from climate research, physical oceanography, biogeochemistry, biogeography, and trophic ecology with economical information provides a strong foundation to produce scientific knowledge that can support a multisectoral management of ecosystems.

  • 3. Eero, Margit
    et al.
    Hjelm, Joakim
    Behrens, Jane
    Buchmann, Kurt
    Cardinale, Massimiliano
    Casini, Michele
    Gasyukov, Pavel
    Holmgren, Noel
    Horbowy, Jan
    Hussy, Karin
    Kirkegaard, Eskild
    Kornilovs, Georgs
    Krumme, Uwe
    Koster, Friedrich W.
    Oeberst, Rainer
    Plikshs, Maris
    Radtke, Krzysztof
    Raid, Tiit
    Schmidt, Joern
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Vinther, Morten
    Zimmermann, Christopher
    Storr-Paulsen, Marie
    Food for Thought Eastern Baltic cod in distress: biological changes and challenges for stock assessment2015In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 72, no 8, p. 2180-2186Article in journal (Refereed)
    Abstract [en]

    The eastern Baltic (EB) cod (Gadus morhua) stock was depleted and overexploited for decades until the mid-2000s, when fishing mortality rapidly declined and biomass started to increase, as shown by stock assessments. These positive developments were partly assigned to effective management measures, and the EB cod was considered one of the most successful stock recoveries in recent times. In contrast to this optimistic view, the analytical stock assessment failed in 2014, leaving the present stock status unclear. Deteriorated quality of some basic input data for stock assessment in combination with changes in environmental and ecological conditions has led to an unusual situation for cod in the Baltic Sea, which poses new challenges for stock assessment and management advice. A number of adverse developments such as low nutritional condition and disappearance of larger individuals indicate that the stock is in distress. In this study, we (i) summarize the knowledge of recent changes in cod biology and ecosystem conditions, (ii) describe the subsequent challenges for stock assessment, and (iii) highlight the key questions where answers are urgently needed to understand the present stock status and provide scientifically solid support for cod management in the Baltic Sea.

  • 4. Gårdmark, Anna
    et al.
    Lindegren, Martin
    Neuenfeldt, Stefan
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre, Baltic Nest Institute.
    Heikinheimo, Outi
    Müller-Karulis, Barbel
    Stockholm University, Faculty of Science, Stockholm Resilience Centre, Baltic Nest Institute. Institute of Food Safety, Animal Health and Environment BIOR, Latvia.
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre, Baltic Nest Institute.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre, Baltic Nest Institute.
    Aro, Eero
    Wikström, Anders
    Moellmann, Christian
    Biological ensemble modeling to evaluate potential futures of living marine resources2013In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 23, no 4, p. 742-754Article in journal (Refereed)
    Abstract [en]

    Natural resource management requires approaches to understand and handle sources of uncertainty in future responses of complex systems to human activities. Here we present one such approach, the biological ensemble modeling approach,'' using the Eastern Baltic cod (Gadus morhua callarias) as an example. The core of the approach is to expose an ensemble of models with different ecological assumptions to climate forcing, using multiple realizations of each climate scenario. We simulated the long-term response of cod to future fishing and climate change in seven ecological models ranging from single-species to food web models. These models were analyzed using the biological ensemble modeling approach'' by which we (1) identified a key ecological mechanism explaining the differences in simulated cod responses between models, (2) disentangled the uncertainty caused by differences in ecological model assumptions from the statistical uncertainty of future climate, and (3) identified results common for the whole model ensemble. Species interactions greatly influenced the simulated response of cod to fishing and climate, as well as the degree to which the statistical uncertainty of climate trajectories carried through to uncertainty of cod responses. Models ignoring the feedback from prey on cod showed large interannual fluctuations in cod dynamics and were more sensitive to the underlying uncertainty of climate forcing than models accounting for such stabilizing predator-prey feedbacks. Yet in all models, intense fishing prevented recovery, and climate change further decreased the cod population. Our study demonstrates how the biological ensemble modeling approach makes it possible to evaluate the relative importance of different sources of uncertainty in future species responses, as well as to seek scientific conclusions and sustainable management solutions robust to uncertainty of food web processes in the face of climate change.

  • 5. Heymans, Johanna J.
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Regime shifts in the Northern Benguela ecosystem: Challenges for management2016In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 331, p. 151-159Article in journal (Refereed)
    Abstract [en]

    An existing Ecopath with Ecosim model of the Northern Benguela ecosystem for 1956, previously fitted to time series for 50 years, was used to describe the impact that the different pressures (fishing and climate drivers) had on the structure of the ecosystem. Ecological network analysis indices and Integrated Trend Assessment of the input data and model outputs were used to describe the changes in this ecosystem over time. We test the hypothesis that the system has been reorganised over the course of the past 50 years, probably due to the cumulative effects of overfishing and environmental drivers such as the Benguela Nifio, showing two large changes, with a transition period between the early 1970s and the early 1980s. The ecosystem has moved into a new stable state and this reorganised system will need a large shift to change with the consequential change not necessarily being back towards the pre-existing system.

  • 6. Horbowy, Jan
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Extension of biomass estimates to pre-assessment periods using density dependent surplus production approach2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 11, article id e0186830Article in journal (Refereed)
    Abstract [en]

    Biomass reconstructions to pre-assessment periods for commercially important and exploitable fish species are important tools for understanding long-term processes and fluctuation on stock and ecosystem level. For some stocks only fisheries statistics and fishery dependent data are available, for periods before surveys were conducted. The methods for the backward extension of the analytical assessment of biomass for years for which only total catch volumes are available were developed and tested in this paper. Two of the approaches developed apply the concept of the surplus production rate (SPR), which is shown to be stock density dependent if stock dynamics is governed by classical stock-production models. The other approach used a modified form of the Schaefer production model that allows for backward biomass estimation. The performance of the methods was tested on the Arctic cod and North Sea herring stocks, for which analytical biomass estimates extend back to the late 1940s. Next, the methods were applied to extend biomass estimates of the North-east Atlantic mackerel from the 1970s (analytical biomass estimates available) to the 1950s, for which only total catch volumes were available. For comparison with other methods which employs a constant SPR estimated as an average of the observed values, was also applied. The analyses showed that the performance of the methods is stock and data specific; the methods that work well for one stock may fail for the others. The constant SPR method is not recommended in those cases when the SPR is relatively high and the catch volumes in the reconstructed period are low.

  • 7. Lassalle, Geraldine
    et al.
    Lobry, Jeremy
    Le Loc'h, Francois
    Mackinson, Steven
    Sanchez, Francisco
    Tomczak, Maciej Tomasz
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Niquil, Nathalie
    Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves2013In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 70, no 1, p. 135-149Article in journal (Refereed)
    Abstract [en]

    This work aimed to provide a better understanding of how the structure and function of marine ecosystems and trophic control mechanisms influence their response to perturbations. Comparative analysis of Ecopath models of four Northeast Atlantic ecosystems was used to search for rules of thumb defining the similarities and differences between them. Ecosystem indicators, related to the ecology of species interactions, were derived from these models and compared. Two main questions were addressed. (i) What are the main energy pathways and mechanisms of control? (ii) Do these ecosystems exhibit the widespread and potentially stabilizing food-web structure such that top predators couple distinct energy pathways? A strong bentho-pelagic coupling operated over the Bay of Biscay Shelf, while energy reached higher trophic levels mostly through pelagic compartments, in northern areas. Zooplankton was demonstrated to be trophically important in all ecosystems, acting as a regulator of the abundance of small pelagic fish. A latitudinal pattern in flow control was highlighted by this analysis, with a significant contribution of top-down effect at higher latitudes. This top-down control of the Baltic Sea, combined with the fact that this ecosystem did not exhibit the potentially stabilizing two-channel structure, suggested a non-stable environment.

  • 8. Longo, C.
    et al.
    Hornborg, S.
    Bartolino, V.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ciannelli, L.
    Libralato, S.
    Belgrano, A.
    Role of trophic models and indicators in current marine fisheries management2015In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 538, p. 257-272Article, review/survey (Refereed)
    Abstract [en]

    The previous decade has witnessed a flourishing of studies on how fisheries and marine food webs interact, and how trophic models and indicators can be used for assessment and management purposes. Acknowledging the importance of complex interactions among species, fishermen and the environment has led to a shift from single species to an ecosystem-wide approach in the science supporting fisheries management (e.g. Johannesburg Declaration, Magnuson-Stevens Act). Moreover, fisheries managers today acknowledge that fishing activities are linked to a range of societal benefits and services, and their work is necessarily a multi-objective practice (i.e. ecosystem-based management). We argue that the knowledge accumulated thus far points to tropho-dynamic models and indicators as key tools for such multi-dimensional assessments. Nevertheless, trophodynamic approaches are still underutilised in fisheries management. More specifically, most management decisions continue to rely on single species and sector-specific models. Here we review examples of applications of trophodynamic indicators within fisheries assessments in well-studied ecosystems, and discuss progress made (as well as lack thereof) towards increased integration of these metrics into marine resource management. Having clarified how trophic indicators fit within current policy and management contexts, we propose ways forward to increase their use in view of future management challenges.

  • 9. MacKenzie, Brian R.
    et al.
    Meier, H. E. Markus
    Lindegren, Martin
    Neuenfeldt, Stefan
    Eero, Margit
    Blenckner, Thorsten
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Tomczak, Maciej T.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Niiranen, Susa
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Impact of Climate Change on Fish Population Dynamics in the Baltic Sea: A Dynamical Downscaling Investigation2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 626-636Article in journal (Refereed)
    Abstract [en]

    Understanding how climate change, exploitation and eutrophication will affect populations and ecosystems of the Baltic Sea can be facilitated with models which realistically combine these forcings into common frameworks. Here, we evaluate sensitivity of fish recruitment and population dynamics to past and future environmental forcings provided by three ocean-biogeochemical models of the Baltic Sea. Modeled temperature explained nearly as much variability in reproductive success of sprat (Sprattus sprattus; Clupeidae) as measured temperatures during 1973-2005, and both the spawner biomass and the temperature have influenced recruitment for at least 50 years. The three Baltic Sea models estimate relatively similar developments (increases) in biomass and fishery yield during twenty-first century climate change (ca. 28 % range among models). However, this uncertainty is exceeded by the one associated with the fish population model, and by the source of global climate data used by regional models. Knowledge of processes and biases could reduce these uncertainties.

  • 10. Moellmann, Christian
    et al.
    Lindegren, Martin
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Bergström, Lena
    Casini, Michele
    Diekmann, Rabea
    Flinkman, Juha
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Neuenfeldt, Stefan
    Schmidt, Joern O.
    Tomczak, Maciej
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Voss, Ruediger
    Gårdmark, Anna
    Implementing ecosystem-based fisheries management: from single-species to integrated ecosystem assessment and advice for Baltic Sea fish stocks2014In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 71, no 5, p. 1187-1197Article in journal (Refereed)
    Abstract [en]

    Theory behind ecosystem-based management (EBM) and ecosystem-based fisheries management (EBFM) is now well developed. However, the implementation of EBFM exemplified by fisheries management in Europe is still largely based on single-species assessments and ignores the wider ecosystem context and impact. The reason for the lack or slow implementation of EBM and specifically EBFM is a lack of a coherent strategy. Such a strategy is offered by recently developed integrated ecosystem assessments (IEAs), a formal synthesis tool to quantitatively analyse information on relevant natural and socio-economic factors, in relation to specified management objectives. Here, we focus on implementing the IEA approach for Baltic Sea fish stocks. We combine both tactical and strategic management aspects into a single strategy that supports the present Baltic Sea fish stock advice, conducted by the International Council for the Exploration of the Sea (ICES). We first review the state of the art in the development of IEA within the current management framework. We then outline and discuss an approach that integrates fish stock advice and IEAs for the Baltic Sea. We intentionally focus on the central Baltic Sea and its three major fish stocks cod (Gadus morhua), herring (Clupea harengus), and sprat (Sprattus sprattus), but emphasize that our approach may be applied to other parts and stocks of the Baltic, as well as other ocean areas.

  • 11. 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.

  • 12.
    Niiranen, Susa
    et al.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Blenckner, Thorsten
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Tomczak, Maciej T.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Uncertainties in a Baltic Sea Food-Web Model Reveal Challenges for Future Projections2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 613-625Article in journal (Refereed)
    Abstract [en]

    Models that can project ecosystem dynamics under changing environmental conditions are in high demand. The application of such models, however, requires model validation together with analyses of model uncertainties, which are both often overlooked. We carried out a simplified model uncertainty and sensitivity analysis on an Ecopath with Ecosim food-web model of the Baltic Proper (BaltProWeb) and found the model sensitive to both variations in the input data of pre-identified key groups and environmental forcing. Model uncertainties grew particularly high in future climate change scenarios. For example, cod fishery recommendations that resulted in viable stocks in the original model failed after data uncertainties were introduced. In addition, addressing the trophic control dynamics produced by the food-web model proved as a useful tool for both model validation, and for studying the food-web function. These results indicate that presenting model uncertainties is necessary to alleviate ecological surprises in marine ecosystem management.

  • 13.
    Niiranen, Susa
    et al.
    Stockholm University, Stockholm Resilience Centre.
    Blenckner, Thorsten
    Stockholm University, Stockholm Resilience Centre.
    Yletyinen, Johanna
    Stockholm University, Stockholm Resilience Centre.
    Otto, Saskia
    Stockholm University, Stockholm Resilience Centre.
    Meier, H. E. Markus
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tomczak, Maciej T
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    The potential risk of regime shifts and changes in ecosystem dynamics in the future Baltic SeaArticle in journal (Refereed)
  • 14.
    Niiranen, Susa
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Yletyinen, Johanna
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Olso, Norway.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    MacKenzie, Brian R.
    Müller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Neumann, Thomas
    Meier, H. E. Markus
    Stockholm University, Faculty of Science, Department of Meteorology . Swedish Meteorological and Hydrological Institute, Sweden.
    Combined effects of global climate change and regional ecosystem drivers on an exploited marine food web2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 11, p. 3327-3342Article in journal (Refereed)
    Abstract [en]

    Changes in climate, in combination with intensive exploitation of marine resources, have caused large-scale reorganizations in many of the world's marine ecosystems during the past decades. The Baltic Sea in Northern Europe is one of the systems most affected. In addition to being exposed to persistent eutrophication, intensive fishing, and one of the world's fastest rates of warming in the last two decades of the 20th century, accelerated climate change including atmospheric warming and changes in precipitation is projected for this region during the 21st century. Here, we used a new multi-model approach to project how the interaction of climate, nutrient loads and cod fishing may affect the future of the open Central Baltic Sea food web. Regionally downscaled global climate scenarios were, in combination with three nutrient load scenarios, used to drive an ensemble of three regional biogeochemical models (BGMs). An Ecopath with Ecosim food web model was then forced with the BGM results from different nutrient-climate scenarios in combination with two different cod fishing scenarios. The results showed that regional management is likely to play a major role in determining the future of the Baltic Sea ecosystem. By the end of the 21st century, for example, the combination of intensive cod fishing and high nutrient loads projected a strongly eutrophicated and sprat-dominated ecosystem, while low cod fishing in combination with low nutrient loads resulted in a cod-dominated ecosystem with eutrophication levels close to present. Also, non-linearities were observed in the sensitivity of different trophic groups to nutrient loads or fishing depending on the combination of the two. Finally, many climate variables and species biomasses were projected to levels unseen in the past. Hence, the risk for ecological surprises needs to be addressed, particularly when the results are discussed in the ecosystem-based management context.

  • 15. Olsson, Jens
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ojaveer, Henn
    Gårdmark, Anna
    Pöllumäe, Arno
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ustups, Didzis
    Dinesen, Grete E.
    Peltonen, Heikki
    Putnis, Ivars
    Szymanek, Lena
    Simm, Mart
    Heikinheimo, Outi
    Gasyukov, Pavel
    Axe, Philip
    Bergström, Lena
    Temporal development of coastal ecosystems in the Baltic Sea over the past two decades2015In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 72, no 9, p. 2539-2548Article in journal (Refereed)
    Abstract [en]

    Coastal areas are among the most biologically productive aquatic systems worldwide, but face strong and variable anthropogenic pressures. Few studies have, however, addressed the temporal development of coastal ecosystems in an integrated context. This study represents an assessment of the development over time in 13 coastal ecosystems in the Baltic Sea region during the past two decades. The study covers between two to six trophic levels per system and time-series dating back to the early 1990s. We applied multivariate analyses to assess the temporal development of biological ecosystem components and relate these to potential driving variables associated with changes in climate, hydrology, nutrient status, and fishing pressure. Our results show that structural change often occurred with similar timing in the assessed coastal systems. Moreover, in 10 of the 13 systems, a directional development of the ecosystem components was observed. The variables representing key ecosystem components generally differed across systems, due to natural differences and limitation to available data. As a result of this, the correlation between the temporal development of the biological components in each area and the driving variables assessed was to some extent area-specific. However, change in nutrient status was a common denominator of the variables most often associated with changes in the assessed systems. Our results, additionally, indicate existing strengths as well as future challenges in the capacity of currently available monitoring data to support integrated assessments and the implementation of an integrated ecosystem-based approach to the management of the Baltic Sea coastal ecosystems.

  • 16. Pinnegar, John K.
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Link, Jason S.
    How to determine the likely indirect food-web consequences of a newly introduced non-native species: A worked example2014In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 272, p. 379-387Article in journal (Refereed)
    Abstract [en]

    In this paper we demonstrate through a worked case-study that it is possible to make an assessment of the indirect food-web consequences that might occur as a result of the arrival of a hither-to not observed non-native species. We also explore implications for commercial fisheries catches, through the application of a suite of complimentary ecosystem modelling tools. Fistularia commersonii is a lessepsian migrant (introduced via the Suez Canal) that was first recorded in the Mediterranean in January 2000. It has since spread throughout the basin and has been described as the fastest and farthest spreading lessepsian fish migrant ever recorded'. We have used a Rank Proportion Algorithm (RPA) model to predict the theoretical diet composition of F. commersonii in the Bay of Calvi, Corsica. We did so based on potential prey abundances, as well as morphological and behavioural characteristics of both the prey and this novel predator. The 'predicted' diet composition of F. commersonii derived from the RPA analysis was then used as input to an Ecopath with Ecosim (EwE) model. This model was used to simulate possible consequences of introducing this invasive species, assuming different rates of expansion of F. commersonii populations in the region. Increases in the F. commersonii population resulted in a marked decline in certain prey types (notably planktivorous fish, Mullus surmuletus and Symphodus tinca). By contrast, seabirds and piscivorous fish were suggested as possible beneficiaries, although this depended heavily on model and scenario assumptions. Overall fisheries catches were projected to increase, and this reflected an anticipated 'bottom up' increase in piscivorous fish that are the main target of the commercial fishery in the Bay of Calvi region.

  • 17. Tam, Jamie C.
    et al.
    Link, Jason S.
    Rossberg, Axel G.
    Rogers, Stuart I.
    Levin, Philip S.
    Rochet, Marie-Joelle
    Bundy, Alida
    Belgrano, Andrea
    Libralato, Simone
    Tomczak, Maciej
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    van de Wolfshaar, Karen
    Pranovi, Fabio
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Large, Scott I.
    Niquil, Nathalie
    Greenstreet, Simon P. R.
    Druon, Jean-Noel
    Lesutiene, Jurate
    Johansen, Marie
    Preciado, Izaskun
    Patricio, Joana
    Palialexis, Andreas
    Tett, Paul
    Johansen, Geir O.
    Houle, Jennifer
    Rindorf, Anna
    Towards ecosystem-based management: identifying operational food-web indicators for marine ecosystems2017In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 74, no 7, p. 2040-2052Article in journal (Refereed)
    Abstract [en]

    Modern approaches to Ecosystem-Based Management and sustainable use of marine resources must account for the myriad of pressures (interspecies, human and environmental) affecting marine ecosystems. The network of feeding interactions between co-existing species and populations (food webs) are an important aspect of all marine ecosystems and biodiversity. Here we describe and discuss a process to evaluate the selection of operational food-web indicators for use in evaluating marine ecosystem status. This process brought together experts in food-web ecology, marine ecology, and resource management, to identify available indicators that can be used to inform marine management. Standard evaluation criteria (availability and quality of data, conceptual basis, communicability, relevancy to management) were implemented to identify practical food-web indicators ready for operational use and indicators that hold promise for future use in policy and management. The major attributes of the final suite of operational food-web indicators were structure and functioning. Indicators that represent resilience of the marine ecosystem were less developed. Over 60 potential food-web indicators were evaluated and the final selection of operational food-web indicators includes: the primary production required to sustain a fishery, the productivity of seabirds (or charismatic megafauna), zooplankton indicators, primary productivity, integrated trophic indicators, and the biomass of trophic guilds. More efforts should be made to develop thresholds-based reference points for achieving Good Environmental Status. There is also a need for international collaborations to develop indicators that will facilitate management in marine ecosystems used by multiple countries.

  • 18.
    Tomczak, Macief
    et al.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Niiranen, Susa
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Blenckner, Thorsten
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Ecosystem flow dynamics in the Baltic Proper-Using a multi-trophic dataset as a basis for food-web modelling2012In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 230, p. 123-147Article in journal (Refereed)
    Abstract [en]

    The Baltic Proper is a semi-enclosed, highly productive basin of the Baltic Sea with a low biodiversity, where only a few key species drive the system's dynamics. Recently, an ecosystem regime shift was described having pronounced changes at all trophic levels, driven by changes in fishery and climate and leading to a food-web reorganisation. An Ecopath with Ecosim Baltic Proper food-web model (BaltProWeb) was developed to simulate and better understand trophic interactions and their flows. The model contains 22 functional groups that represent the main food-web components. BaltProWeb was calibrated to long-term monitoring data (1974-2006), covering multiple trophic levels and is forced by fisheries and environmental drivers. Our model enables the quantification of the flows through the food-web from primary producers to top predators including fisheries over time. The model is able to explain 51% of the variation in biomass of multiple trophic levels and to simulate the regime shift from a cod dominated to a sprat dominated system. Results show a change from benthic to more pelagic trophic flows. Before the reorganisation macrozoobenthos was identified as an important functional group transferring energy directly from lower trophic levels to top predators. After the regime shift, the pelagic trophic flows dominated. Uncertainties and limitations of the modelling approach and results in relation to ecosystem-based management are discussed.

  • 19.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Technical University of Denmark, Denmark.
    Dinesen, Grete E.
    Hoffmann, Erik
    Maar, Marie
    Stottrup, Josianne G.
    Integrated trend assessment of ecosystem changes in the Limfjord (Denmark): Evidence of a recent regime shift?2013In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 117, p. 178-187Article in journal (Refereed)
    Abstract [en]

    An integrated ecosystem assessment was carried out for the Limfjord over the period from 1984 to 2008 to describe changes in ecosystem structure and potentially important drivers. The Limfjord is a eutrophic transitional Danish fjord system with the main inflow from the North Sea in the west and main outflow to the Kattegat in the east. We showed that from 1990 to 1995, the ecosystem structure shifted from dominance by demersal fish species (eelpout, whiting, flounder, plaice) to that of pelagic fish species (sprat, herring, sticklebacks), small-bodied fish species (black goby, pipefish), jellyfish, common shore crab, starfish and blue mussels. We interpret this change as a regime shift that showed a similar temporal pattern to regime shifts identified in adjacent seas. The observed changes in trophic interactions and food web reorganisation suggested a non-linear regime shift. The analyses further showed the regime shift to be driven by a combination of anthropogenic pressures and possible interplay with climatic disturbance.

  • 20.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Heymans, Johanna J.
    Yletyinen, Johanna
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change ((NorMER).
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Otto, Saskia A.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Ecological Network Indicators of Ecosystem Status and Change in the Baltic Sea2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 10, article id e75439Article in journal (Refereed)
    Abstract [en]

    Several marine ecosystems under anthropogenic pressure have experienced shifts from one ecological state to another. In the central Baltic Sea, the regime shift of the 1980s has been associated with food-web reorganization and redirection of energy flow pathways. These long-term dynamics from 1974 to 2006 have been simulated here using a food-web model forced by climate and fishing. Ecological network analysis was performed to calculate indices of ecosystem change. The model replicated the regime shift. The analyses of indicators suggested that the system's resilience was higher prior to 1988 and lower thereafter. The ecosystem topology also changed from a web-like structure to a linearized food-web.

  • 21.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Szymanek, L.
    Pastuszak, M.
    Grygiel, W.
    Zalewski, M.
    Gromisz, S.
    Ameryk, A.
    Kownacka, J.
    Psuty, I.
    Kuzebski, E.
    Grzebielec, R.
    Margonski, P.
    Evaluation of Trends and Changes in the Gulf of Gdansk Ecosystem-an Integrated Approach2016In: Estuaries and Coasts, ISSN 1559-2723, E-ISSN 1559-2731, Vol. 39, no 3, p. 593-604Article in journal (Refereed)
    Abstract [en]

    An integrated trend assessment was conducted for the Gulf of GdaAsk (GoG), Baltic Sea for the period 1994-2010 to describe changes and potentially important drivers of the ecosystem. We found changes in the biota, including an increase in open sea taxa (flatfish, sprat and cod), a decrease in typical coastal species such as eelpout and lumpfish and an increase in primary production. The analyses further suggest that changes in the food web were driven by a combination of anthropogenic pressures (e.g., nutrient loadings and fisheries) and possible interactions with climatic disturbance. Our analyses show that significant changes occurred in the GoG ecosystem between 1994 and 2010. The primary drivers and mechanisms of these changes are discussed. We describe this alteration of the GoG within the context of similar temporal patterns identified in adjacent areas.

  • 22. Uusitalo, Laura
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Putnis, Ivars
    Trifonova, Neda
    Tucker, Allan
    Hidden variables in a Dynamic Bayesian Network identify ecosystem level change2018In: Ecological Informatics, ISSN 1574-9541, E-ISSN 1878-0512, Vol. 45, p. 9-15Article in journal (Refereed)
    Abstract [en]

    Ecosystems are known to change in terms of their structure and functioning over time. Modelling this change is a challenge, however, as data are scarce, and models often assume that the relationships between ecosystem components are invariable over time. Dynamic Bayesian Networks (DBN) with hidden variables have been proposed as a method to overcome this challenge, as the hidden variables can capture the unobserved processes. In this paper, we fit a series of DBNs with different hidden variable structures to a system known to have undergone a major structural change, i.e. the Baltic Sea food web. The exact setup of the hidden variables did not considerably affect the result, and the hidden variables picked up a pattern that agrees with previous research on the system dynamics.

  • 23. 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, E-ISSN 2296-7745, 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.

  • 24.
    Österblom, Henrik
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Merrie, Andrew
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Metian, Marc
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Boonstra, Wiebren J.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Watson, James R.
    Rykaczewski, Ryan R.
    Ota, Yoshitaka
    Sarmiento, Jorge L.
    Christensen, Villy
    Schlüter, Maja
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Birnbaum, Simon
    Stockholm University, Faculty of Social Sciences, Department of Political Science. Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Troell, Max
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Folke, Carl
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Modeling Social—Ecological Scenarios in Marine Systems2013In: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 63, no 9, p. 735-744Article in journal (Refereed)
    Abstract [en]

    Human activities have substantial impacts on marine ecosystems, including rapid regime shifts with large consequences for human well-being. We highlight the use of model-based scenarios as a scientific tool for adaptive stewardship in the face of such consequences. The natural sciences have a long history of developing scenarios but rarely with an in-depth understanding of factors influencing human actions. Social scientists have traditionally investigated human behavior, but scholars often argue that behavior is too complex to be repre-ented by broad generalizations useful for models and scenarios. We address this scientific divide with a framework for integrated marine social ecological scenarios, combining quantitative process-based models from the biogeochemical and ecological disciplines with qualitative studies on governance and social change. The aim is to develop policy-relevant scenarios based on an in-depth empirical understanding from both the natural and the social sciences, thereby contributing to adaptive stewardship of marine social-ecological systems.

1 - 24 of 24
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