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| 2. |
- Bekkevold, Dorte, et al.
(författare)
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Mixed-stock analysis of Atlantic herring (Clupea harengus) : a tool for identifying management units and complex migration dynamics
- 2023
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press. - 1054-3139 .- 1095-9289. ; 80:1, s. 173-184
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Tidskriftsartikel (refereegranskat)abstract
- We developed and validated a mixed-stock analysis (MSA) method with 59 single-nucleotide polymorphisms selected from genome-wide data to assign individuals to populations in mixed-stock samples of Atlantic herring from the North and Baltic seas. We analysed 3734 herring from spawning locations and scientific catches of mixed feeding stocks to demonstrate a "one-fits-all" tool with unprecedented accuracy for monitoring spatio-temporal dynamics throughout a large geographical range with complex stock mixing. We re-analysed time-series data (2002-2021) and compared inferences about stock composition with estimates from morphological data. We show that contributions from the western Baltic spring-spawning stock complex, which is under management concern, have likely been overestimated. We also show that a genetically distinctive population of western Baltic autumn spawners, ascribed low fisheries importance, contributes non-negligible and potentially temporally increasing proportions to mixed-stock aggregations, calling for a re-evaluation of stock definitions. MSA data can be implemented in stock assessment and in a variety of applications, including marine ecosystem description, impact assessment of specific fleets, and stock-rebuilding plans.
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| 3. |
- Eero, Margit, et al.
(författare)
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Use of food web knowledge in environmental conservation and management of living resources in the Baltic Sea
- 2021
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 78:8, s. 2645-2663
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Forskningsöversikt (refereegranskat)abstract
- Food webs are central entities mediating processes and external pressures in marine ecosystems. They are essential to understand and predict ecosystem dynamics and provision of ecosystem services. Paradoxically, utilization of food web knowledge in marine environmental conservation and resource management is limited. To better understand the use of knowledge and barriers to incorporation in management, we assess its application related to the management of eutrophication, chemical contamination, fish stocks, and non-indigenous species. We focus on the Baltic, a severely impacted, but also intensely studied and actively managed semi-enclosed sea. Our assessment shows food web processes playing a central role in all four areas, but application varies strongly, from formalized integration in management decisions, to support in selecting indicators and setting threshold values, to informal knowledge explaining ecosystem dynamics and management performance. Barriers for integration are complexity of involved ecological processes and that management frameworks are not designed to handle such information. We provide a categorization of the multi-faceted uses of food web knowledge and benefits of future incorporation in management, especially moving towards ecosystem-based approaches as guiding principle in present marine policies and directives. We close with perspectives on research needs to support this move considering global and regional change.
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| 4. |
- MacKenzie, Brian R., et al.
(författare)
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Multi-decadal scale variability in the eastern Baltic cod fishery 1550-1860 - Evidence and causes
- 2007
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 87:2-3, s. 106-119
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Tidskriftsartikel (refereegranskat)abstract
- Identification of periods of high and low cod production, and the reasons for these periods, can increase understanding of variability in populations and ecosystems. In this study we investigate the multi-decadal and multi-century scale variations in the cod population in the eastern Baltic Sea (ICES Subdivisions 25-32). Analytically derived estimates of biomass are available since 1966. These estimates show that biomass increased in the late 1970s-early 1980s, but decreased nearly 10-fold until the early 1990s and is still well below the long-term average. Prior to 1966 the biomass of cod is unknown, as is the relative role of fishing, climate variability/regimes, eutrophication and reduction of marine mammal predator populations. We have begun to investigate whether historical fisheries information (landings, effort, distribution) from before the 1880s is available in Baltic archives and museums, and to what extent this information can be used to interpret variations in this population. We have located fisheries data for different parts of the Baltic for different time periods since the 1550s and have interpreted the findings using current process knowledge of oceanographic mechanisms affecting cod reproduction and ecology in the Baltic Sea. The recovered data show that the Baltic ecosystem was able to support modest-large cod populations even though it was oligotrophic and contained large populations of cod predators (e.g., marine mammals). Current ecosystem management policy in the Baltic as developed and implemented by organisations such as the International Council for the Exploration of the Sea (ICES), the Baltic Marine Environment Protection Commission (HELCOM), the nine coastal countries and the European Union includes recovery of the cod population, a reduction in nutrient loading and measures to promote recovery of seal and harbour porpoise populations. If these policies are successful, the role of predatory fish in the future Baltic could again be substantial and comparable to that which we show existed 450 years ago. However, such a scenario will also require a major reduction in cod fishing mortality and suitable hydrographic conditions which promote successful cod reproduction. Historical ecology investigations in the Baltic can contribute to scientifically based fishery and ecosystem management and recovery plans.
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| 5. |
- Neuenfeldt, Stefan, et al.
(författare)
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Review of trophic models for the Baltic Sea
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This review aims to be a representative overview over the available types of trophic models in order to investigate, if their output can be used to quantify existing food-web indicators for the EU Marine Strategy Framework Directive (MSFD) . The goal is to obtain a comprehensive picture of the applicability of various model approaches to contribute to achieving MSFD objectives. The work will feed into XWEBS Task 3.3 on ’ Evaluation of the model application potential’. In total we have identified 27 food-web related models with different application areas in the Baltic Sea. We highlight the specific purpose for which each model was designed and the key assumptions underlying each model.The assessment of model applicability here is focused on strengths and gaps of the models to realistically depict size and dynamics of functional groups in the Baltic Sea food web. Based on the latter, we illustrate existing gaps in the models, and assess the extent to which the models can be applied to represent status and dynamics of the Baltic Sea food webs. For the future, we recommend to use an ensemble approach where possible to determine guild biomasses as indicators for food web status. Spatial heterogeneity should be accounted for. This issue should be initiated by collecting all relevant processes in the Baltic Sea, such as source-sinks or coastal-offshore connectivity. The spatial and temporal scale of ecosystem models and potential food web indicators should be aligned as far as possible, and following functional criteria, such as topographic differences and known separated community structures. This way, one can avoid erroneous conclusions that are based on limited data projected over the whole Baltic.
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| 6. |
- Ojaveer, Henn, et al.
(författare)
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Swedish Baltic Sea fisheries during 1868-1913 : Spatio-temporal dynamics of catch and fishing effort
- 2007
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 87:2-3, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- The current paper summarizes catch and effort data for Swedish fisheries in the Baltic Sea prior to the standardized recording of fish catches, evaluates spatial and temporal variations and gives interpretations of selected findings. Long-term datasets (1868-1913) of species having different environmental preferences (and of different origin) - marine, migratory and freshwater - are presented for several Swedish counties extending from the Bothnian Bay to the Bornholm Basin. Herring (Clupea harengus membras) was the most important commercial fish-based on landings and also on the amount of historical records available. In addition, herring landings have undoubtedly fluctuated the most. Other commercially important fish were cod (Gadus morhua), salmon and trout (Salmo spp.), flounder (Platichthys flesus), eel (Anguilla anguilla) and whitefish (Coregonus lavaretus). Different species exhibited different patterns of catch dynamics. In general, the 1880s and the 1890s can be characterized as 'good fishing years' for the Swedish Baltic fisheries: catches of herring and cod were high while fishing effort indices were relatively stable. Sprat was not represented in the catch data and may have been recorded as herring. For several species, regions and time periods, catch-effort relationship exhibited clear coupling. However, in several cases, insufficient or lack of effort-related information hampered data interpretations. In summary, the Swedish fisheries during the late 19th century generally exploited the same species as presently (including a dominance by clupeids), but the relative contributions of individual species have changed.
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| 7. |
- Olsson, Jens, et al.
(författare)
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Temporal development of coastal ecosystems in the Baltic Sea over the past two decades
- 2015
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 72:9, s. 2539-2548
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Pederson, Judith, et al.
(författare)
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ICES WGITMO Report 2009 to OSPAR Report
- 2009
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Ingår i: ICES Report of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) 11-13, 2009, Washington D.C., USA. ; ICES 2009/ACOM 25, s. 143-176
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Puntila, Riikka, et al.
(författare)
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Baseline survey of non-indigenous species in the Baltic Sea ports -Testing and evaluating the HELCOM-OSPAR Port Survey Protocol
- 2015
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Ingår i: ICES Annual Science Conference.
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Konferensbidrag (refereegranskat)abstract
- Transport and introductions of non-indigenous species (NIS) is perceived as one of the primary threats to the diversity and productivity of the coastal ecosystems worldwide. One of the most important vectors for aquatic organisms is shipping and ports act as key locations for new species arrivals. The Baltic Sea is subject to very intense shipping and as a result facing an increasing load of NIS. Ports are often the first arrival locations for new species and they often offer a variety of potentially hospitable environments. Despite of this vulnerability, there has been no frequent NIS monitoring in place for Baltic Sea ports. The Baltic Sea states, working through HELCOM, have agreed on a Protocol to collect the required information in ports, both for implementing the Ballast Water Management Convention (BWMC) and EU Marine Strategy Framework Directive (MSFD). Currently, port surveys have been conducted in five Baltic Sea countries in nine ports. Based on the results, the methods appear to function well in the challenging port environments. Furthermore, survey results indicate that ports harbour a variety of NIS, which highlights the need for continuous monitoring. However, non-parametric extrapolators of the species accumulation curves show that more sampling effort should be directed to certain variable ports and to certain species groups. Also, the Protocol sampling did not adequately cover the seasonal dynamics of the biota and the surrounding areas. Therefore, reliable risk assessments for exemptions from the BWMC require including additional data from the area.
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