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Keyl F.,Thunen Institute of Sea Fisheries | Keyl F.,University of Hamburg
Hydrobiologia | Year: 2017

Spatial explicit ecology and new regulations call for continuous spatiotemporal data. For marine species, such data hardly can be obtained from observation but need to be modelled from point data. A promising approach is regression kriging that addresses biological response to environmental conditions and spatial autocorrelation in data. Here it was applied to abundance data of North Sea prey fish sprat, Norway pout and herring. Results show seasonal and inter-annual variability of distribution limits, core areas and high abundance areas of all three species. Core areas of sprat and Norway pout are complementary bordering roughly along the 50 m isobaths. Small overlap of the two core areas were found only off the northern English coast. The comparison of North Sea-wide sums with assessment estimates show that the regression kriging approach can reproduce inter-annual dynamics. The outcomes allow assessing the magnitude of the catchability of the employed fishing gear and give evidence of seasonal variation of catchability. Capabilities and restrictions of the applied model and data are discussed in the light of niche theory. Results are of potential use in the assessment of the effects of changed utilization of marine areas in the marine spatial planning framework. © 2017 Springer International Publishing Switzerland

Schluter L.,Leibniz Institute of Marine Science | Lohbeck K.T.,Leibniz Institute of Marine Science | Gutowska M.A.,Leibniz Institute of Marine Science | Gutowska M.A.,Monterey Bay Aquarium Research Institute | And 3 more authors.
Nature Climate Change | Year: 2014

Although ocean warming and acidification are recognized as two major anthropogenic perturbations of today's oceans we know very little about how marine phytoplankton may respond via evolutionary change. We tested for adaptation to ocean warming in combination with ocean acidification in the globally important phytoplankton species Emiliania huxleyi. Temperature adaptation occurred independently of ocean acidification levels. Growth rates were up to 16% higher in populations adapted for one year to warming when assayed at their upper thermal tolerance limit. Particulate inorganic (PIC) and organic (POC) carbon production was restored to values under present-day ocean conditions, owing to adaptive evolution, and were 101% and 55% higher under combined warming and acidification, respectively, than in non-adapted controls. Cells also evolved to a smaller size while they recovered their initial PIC:POC ratio even under elevated CO2 . The observed changes in coccolithophore growth, calcite and biomass production, cell size and elemental composition demonstrate the importance of evolutionary processes for phytoplankton performance in a future ocean. © 2014 Macmillan Publishers Limited. All rights reserved.

Probst W.N.,Thunen Institute of Sea Fisheries | Rau A.,Leibniz Institute for Baltic Sea Research | Oesterwind D.,Leibniz Institute for Baltic Sea Research
Marine Policy | Year: 2016

In 2015 the EU Commission decided to review the structure of the criteria and indicators of the Marine Strategy Framework Directive (MSFD). This paper reviews some shortcomings of the current structure of Descriptor 3 (D3) addressing the status of exploited fish and shellfish stocks and suggests a more operational structure for D3. By reframing D3, the assessments of stock size and size distribution within the stock could be addressed within two distinct criteria. When relating status parameters, such as stock size and size structure to human pressures, the first criterion would assess fishing intensity while the second criterion would assess the selectivity pattern acting upon a fish stock. Within each criterion, the indicators would be embedded within an indicator framework and thereby assigned to predefined indicator types. Three different indicator frameworks were compared and analysed with regards to its operationality within D3, namely pressure-state (p-S), pressure-state-response (PSR) and driver-pressure-state-impact-response (DPSIR) frameworks. P-S or DPSIR were found to be either incomplete in fulfilling the MSFD reporting requirements (p-S) or too complicated to be implemented in the mid-term (DPSIR). PSR thus appears to provide the best compromise between operationality and MSFD requirements and could be applied to criteria within other descriptors to obtain a consistent indicator structure within the MSFD. © 2016 Elsevier Ltd

Groger J.P.,Thunen Institute of Sea Fisheries | Groger J.P.,University of Rostock | Hinrichsen H.-H.,Leibniz Institute of Marine Science | Polte P.,Leibniz Institute for Baltic Sea Research
PLoS ONE | Year: 2014

Climate forcing in complex ecosystems can have profound implications for ecosystem sustainability and may thus challenge a precautionary ecosystem management. Climatic influences documented to affect various ecological functions on a global scale, may themselves be observed on quantitative or qualitative scales including regime shifts in complex marine ecosystems. This study investigates the potential climatic impact on the reproduction success of spring-spawning herring (Clupea harengus) in the Western Baltic Sea (WBSS herring). To test for climate effects on reproduction success, the regionally determined and scientifically well-documented spawning grounds of WBSS herring represent an ideal model system. Climate effects on herring reproduction were investigated using two global indices of atmospheric variability and sea surface temperature, represented by the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO), respectively, and the Baltic Sea Index (BSI) which is a regional-scale atmospheric index for the Baltic Sea. Moreover, we combined a traditional approach with modern time series analysis based on a recruitment model connecting parental population components with reproduction success. Generalized transfer functions (ARIMAX models) allowed evaluating the dynamic nature of exogenous climate processes interacting with the endogenous recruitment process. Using different model selection criteria our results reveal that in contrast to NAO and AMO, the BSI shows a significant positive but delayed signal on the annual dynamics of herring recruitment. The westward influence of the Siberian high is considered strongly suppressing the influence of the NAO in this area leading to a higher explanatory power of the BSI reflecting the atmospheric pressure regime on a North-South transect between Oslo, Norway and Szczecin, Poland. We suggest incorporating climate-induced effects into stock and risk assessments and management strategies as part of the EU ecosystem approach to support sustainable herring fisheries in the Western Baltic Sea. © 2014 Grö ger et al.

Neumann V.,Technical University of Denmark | Koster F.W.,Technical University of Denmark | Schaber M.,Thunen Institute of Sea Fisheries | Eero M.,Technical University of Denmark
ICES Journal of Marine Science | Year: 2014

Cod (Gadus morhua) recruitment in the eastern Baltic Sea is influenced by predation on early life stages by sprat (Sprattus sprattus) and herring (Clupea harengus), which is considered as one of the mechanisms preventing cod recovery in the 1990s. In the light of improved cod recruitment in the second half of the 2000s, new analyses of stomach content of sprat and herring were conducted, to elucidate the contribution of changes in predation pressure on cod recruitment. Comparison of stomach contents of sprat and herring in 2004-2008 with data from the 1990s showed a similar diet composition in the two periods; however, changes were found in the ichthyoplankton abundance and composition in the diet, indicating reduced predation pressure on cod eggs in the most recent period. The abundance of cod eggs in the field, availability of other prey, and horizontal and vertical overlap between predator and prey were investigated as potential factors influencing cod egg predation. © International Council for the Exploration of the Sea 2014. All rights reserved.

Ratz H.-J.,Thunen Institute of Sea Fisheries | Lloret J.,University of Girona
Ocean and Coastal Management | Year: 2016

The three main pillars of the European Common Fisheries Policy, reformed in 2013, consist of minimizing ecological impacts; implementing sustainable exploitation defined by maximum sustainable yield (MSY) for regulated species and introducing landing obligations aimed at reducing the wasteful practice of discarding unwanted catches. These three key elements constitute major challenges for fisheries, their management and fishery scientists whose goal is to provide objective advice. We demonstrate that limiting sustainable catch options may pose rigorous constraints on fishing activities, in particular on so-called mixed fisheries targeting more than one individual stock. In a situation where there are complex restrictions comprising multiple management goals which are sometimes conflicting (e.g. the ‘choke effects’ of reduced catch opportunities due to specific stock conservation needs or market conditions), we propose the application of specific measures for specific fisheries, i.e. deviation from traditional fishery selection patterns, as an option to avert significant losses in yield and economic revenue. Fisheries-specific contributions to general management goals, including unwanted effects, shall be evaluated. Individual fisheries may benefit accordingly through multi-annual management plans with regional-scale reconciliation of sustainable exploitation of living natural resources, food security and socio-economy as potential key elements. © 2016 Elsevier Ltd

Cormon X.,French Research Institute for Exploitation of the Sea | Kempf A.,Thunen Institute of Sea Fisheries | Vermard Y.,French Research Institute for Exploitation of the Sea | Vinther M.,Technical University of Denmark | Marchal P.,French Research Institute for Exploitation of the Sea
ICES Journal of Marine Science | Year: 2016

During the last 15 years, northern European hake (Merluccius merluccius) has increased in abundance, and its spatial distribution has expanded in the North Sea region in correlation with temperature. In a context of global warming, this spatial shift could impact local trophic interactions: direct impacts may affect forage fish through modified predator-prey interactions, and indirect impacts may materialize through competition with other resident predators. For instance, North Sea saithe (Pollachius virens) spatial overlap with hake has increased while saithe spawning-stock biomass has decreased recently notwithstanding a sustainable exploitation. In this context, we investigated the range of potential impacts resulting from most recent hake emergence in the North Sea, with a particular focus on saithe. We carried out a multispecies assessment of North Sea saithe, using the Stochastic MultiSpecies (SMS) model. In addition to top-down processes already implemented in SMS, we built in the model bottom-up processes, relating Norway pout (Trisopterus esmarkii) abundance and saithe weight-at-age. We simulated the effects, on all North Sea species being considered but focusing on Norway pout and saithe, of combining different hake abundance trends scenarios with the inclusion of bottom-up processes in SMS. North Sea saithe FMSY was then evaluated in a multispecies context and contrasted with single-species value. The different scenarios tested revealed a negative impact of hake emergence on saithe biomass, resulting from an increase of predation pressure on Norway pout. These results confirm the competition assumption between saithe and hake in the North Sea and might partially explain the most recent decrease of saithe biomass. This study also highlighted that taking into account bottom-up processes in the stock assessment had a limited effect on the estimation of saithe FMSY which was consistent with single-species value. © International Council for the Exploration of the Sea 2016. All rights reserved.

Fock H.O.,Thunen Institute of Sea Fisheries
Fisheries Research | Year: 2014

Based on historical landings and landings-per-unit-effort data, fishing effort was estimated in the period of 1924-1938 in a study area representing the German exclusive economic zone (EEZ) in the North Sea. Three main trawling fisheries were identified, i.e. the international flatfish fisheries comprising the effort of steam trawlers and motor cutters, the German shrimp fisheries and the industrial inshore fisheries. Except for shrimp trawling, which was performed by beam trawling with one beam per vessel, all historical trawling effort was identified as otter board trawling. The trawling effort increased from 1,131,000 to 1,232,000. h in 1924 to 3,170,000 to 3,836,000. h in 1937 and declined in 1938. The main fishery effort was contributed by the German shrimp fisheries, accounting for a maximum of 2,140,000. h in 1937. In comparison, in 2006, approximately 540,000. h were spent fishing in the trawl fisheries of the study area, comprising effort from small (≤221. kW) to large beam trawlers (>221. kW), shrimp fisheries and otter board trawling. The bulk of the historical effort was concentrated at water depths of 5-20. m. With the implementation of combustion engines and new gear technology, the period of 1924-1938 marked a new era for marine fishing when virtually all space became accessible and, in particular, the trawling of inshore areas increased. © 2014 Elsevier B.V.

Fock H.O.,Thunen Institute of Sea Fisheries | Kraus G.,Thunen Institute of Sea Fisheries
PLoS ONE | Year: 2016

Environmental policies employ metaphoric objectives such as ecosystem health, resilience and sustainable provision of ecosystem services, which influence corresponding sustainability assessments by means of normative settings such as assumptions on system description, indicator selection, aggregation of information and target setting. A heuristic approach is developed for sustainability assessments to avoid ambiguity and applications to the EU Marine Strategy Framework Directive (MSFD) and OSPAR assessments are presented. For MSFD, nineteen different assessment procedures have been proposed, but at present no agreed assessment procedure is available. The heuristic assessment framework is a functional-holistic approach comprising an ex-ante/ex-post assessment framework with specifically defined normative and systemic dimensions (EAEPNS). The outer normative dimension defines the ex-ante/ex-post framework, of which the latter branch delivers one measure of ecosystem health based on indicators and the former allows to account for the multi-dimensional nature of sustainability (social, economic, ecological) in terms of modeling approaches. For MSFD, the ex-ante/ex-post framework replaces the current distinction between assessments based on pressure and state descriptors. The exante and the ex-post branch each comprise an inner normative and a systemic dimension. The inner normative dimension in the ex-post branch considers additive utility models and likelihood functions to standardize variables normalized with Bayesian modeling. Likelihood functions allow precautionary target setting. The ex-post systemic dimension considers a posteriori indicator selection by means of analysis of indicator space to avoid redundant indicator information as opposed to a priori indicator selection in deconstructive-structural approaches. Indicator information is expressed in terms of ecosystem variability by means of multivariate analysis procedures. The application to the OSPAR assessment for the southern North Sea showed, that with the selected 36 indicators 48% of ecosystem variability could be explained. Tools for the ex-ante branch are risk and ecosystem models with the capability to analyze trade-offs, generating model output for each of the pressure chains to allow for a phasing-out of human pressures. The Bayesian measure of ecosystem health is sensitive to trends in environmental features, but robust to ecosystem variability in line with state space models. The combination of the ex-ante and ex-post branch is essential to evaluate ecosystem resilience and to adopt adaptive management. Based on requirements of the heuristic approach, three possible developments of this concept can be envisioned, i.e. a governance driven approach built upon participatory processes, a science driven functional-holistic approach requiring extensive monitoring to analyze complete ecosystem variability, and an approach with emphasis on ex-ante modeling and ex-post assessment of well-studied subsystems. © 2016 Fock, Kraus. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abundance trends and distribution were analyzed for thornback rays Raja clavata in the German Bight (eastern central North Sea) for 3 periods: 1902-1908, 1930-1932, and 1991-2009. Abundances declined until 1932, and after 1991 only 4 specimens were encountered in the area during standard fisheries surveys. During the first period, thornback rays inhabited almost the entire German Bight, while a range reduction was observed for the second period and again after 1991. In the first period, thornback rays were negatively associated with gravel and mud, while no sediment parameter appeared to be significant in the 1930-1932 period. Temporal differences are interpreted as differential impacts of fisheries. At low fishing pressure, habitat asso ciated with feeding grounds was occupied by thornback rays, while with increasing fishing pressure, in accordance with the interference hypothesis, less risky habitat was occupied and as such was less associated with feeding grounds, before fishing pressure ultimately caused extirpation. Local fishing mortality observed in all 3 periods exceeded the extinction level mortality (Fext = 0.84). The shift in habitat use is discussed with respect to the designation of marine protected areas based on distributions of species already under pressure. © The author 2014.

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