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| 2. |
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| 3. |
- Bauer, Barbara, et al.
(författare)
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Reducing eutrophication increases spatial extent of communities supporting commercial fisheries : a model case study
- 2018
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 75:4, s. 1306-1317
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
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| 5. |
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| 6. |
- Bergenius, Mikaela, et al.
(författare)
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Joint NAFO\ICES Pandalus Assessment Working Group (NIPAG)
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The NAFO/ICES Pandalus Assessment Group (NIPAG), met to assess the Pandalus stock in divi-sions 3a and 4a east. The objective was to assess stock status and to draft advice according to the current EU and Norway Long-term Management Strategy (LTMS). The LTMS requires ICES to provide both an update in-year TAC advice for 2021 and an initial TAC advice for the first two quarters of 2022.The length-based Stock Synthesis (SS3) statistical framework was used to assess status of the stock based on updated input data (commercial catches for 2020 and survey catches from January 2021). The assessment demonstrated that the fishing pressure on the stock is below FMSY and that spawning–stock size is below MSY Btrigger and between Bpa and Blim.In accordance with the LTMS reference points and Harvest Control Rules, NIPAG advises that catches in 2021 should be no more than 7166 tonnes, and that catches for the first two quarters of 2022 should be no more than 5554 tonnes. This corresponds to an 18% reduction of the initial catch advice for 2021. This change is partly explained by the realized catches in 2020 being higher than the advised catches (9226 tonnes realized, compared to 8736 tonnes advised) due to discard-ing (285 tonnes) and lack of correction for loss in weight due to on-board boiling (533 tonnes). The preliminary advised catch for 2022 is 52% larger than the advised catch for 2021 mainly because the 2020 and 2021 year classes are estimated to be higher than the 2019 year class.SS3 model diagnostics of the assessment did not indicate any issues with the model fit. There is a positive retrospective bias in SSB and recruitment, and a negative retrospective bias in F, but these are all within the acceptable range (Mohns Rho threshold values) of requiring no action.
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| 7. |
- Bergenius Nord, Mikaela, et al.
(författare)
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Benchmark workshop on Pandalus stocks (WKPRAWN)
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Northern shrimp (Pandalus borealis) in divisions 3.a and 4.a East (Skagerrak and Kattegat and northern North Sea in the Norwegian Deep)An ensemble model was developed to incorporate uncertainty in natural mortality (SS3 model). A distribution of possible natural mortalities at age was constructed based on a suite of M life history and other type models. Three M scenarios were developed: a low, median and high M. An objective weighting approach was used based on model performance statistics and diagnostics to develop the final assessment. The reference points were estimated using a shortcut MSE approach testing a range of fishing mortalities and biomass thresholds in relation to virgin stock size (B0). Northern shrimp (Pandalus borealis) in subareas 1 and 2 (Northeast Arctic)For the Barents Sea stock, the accepted assessment model fell on SPiCT. The commercial CPUE used in the assessment was thoroughly investigated and standardized using a non-spatial model. A spatio-temporal modelling approach (sdmTMB) for the joint Norwegian/Russian Barents Sea Ecosystem Survey (BESS) was presented and compared to the design-based estimators currently used. There was some retrospective error on F/Fmsy but Based on the presented diagnostics, the reference model was considered adequate and acceptable. The standard approach for short-term forecasts and reference points was agreed.Flemish Cap shrimp (NAFO Div. 3M)There was limited progress on the Flemish Cap stock (pra.27.3M). An excellent long-term EU survey from 1988-present is available for the stock covering the period of the moratorium. This shows an increase from 2016 to 2019 with a subsequent decrease. Length-composition data are also available from the survey for this assessment. In future, it may be possible to explore an SS3 model for this stock given the partial and patchy nature of the available data.
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| 8. |
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| 9. |
- Cardinale, Massimiliano, et al.
(författare)
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Benchmark workshop on herring (Clupea harengus) in the Gulf of Bothnia (WKCLuB 2021)
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The assessment for the Gulf of Bothnia herring (SD 3031) in 2019 was not accepted by the Advice Drafting Group and was changed from category 1 to 3. The assessment was not accepted based on the poor retrospective diagnostics where the Mohn’s rho values were above 20% for SSB, F and recruitment. The aim for the Benchmark was to evaluate a new model, Stock Synthesis (SS3) as a candidate for the assessment of Gulf of Bothnia Herring SD30–31 in order to minimize the retrospective pattern previously observed. Following the path of the Benchmark data related issues were revealed. This led to a situation that the benchmark was prolonged one year in order to correct the data related issues. Apart from a misspecification in the model about how the trapnet index was used (abundance index vs. biomass index), the data problem had been related to the acoustic survey. The acoustic survey index used in the assessment was thoroughly examined by the Baltic international fish survey working group (WGBIFS) in a meeting in December 2020. A number of model runs (six prior to meeting, and an additional 16 during the benchmark) were conducted for evaluation at this benchmark. The analysis presented extensive diagnostic tests including the standard ICES criterion related to retrospective patterns. This was considered an enhancement over using one method for accepting or rejecting an assessment. It was noted that the final retrospective pattern had low and acceptable values of Mohn’s rho. In general, the benchmark using the stock synthesis platform with the settings specified during the benchmark are considered acceptable for assessment and advice and have features that should ensure stability as new data are added (e.g. selectivity is assumed to be constant over time).
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| 10. |
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| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Cardinale, Massimiliano, et al.
(författare)
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Scientific, Technical and Economic Committee for Fisheries (STECF) – Consolidated Advice on Fish Stocks of Interest to the European Union (STECF-14-24)
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report represents the STECF review of advice f or stocks of interest to the European Union in all of the world’s oceans. It constitutes a consolidate d version of three reports released by the STECF on r eview of scientific advice in 2014. These reports w ere published as the STECF review of advice for 2015 Parts 1, 2 and 3. However, since the publicati on of the three separate reports, some fisheries ad visory bodies have published additional information and advice and this has been taken into account in the present report. This report therefore supersede s any advice on stocks of EU interest previously gi ven by the STECF for 2015
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Cardinale, Massimiliano, et al.
(författare)
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Workshop on ICES reference points (WKREF1)
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The ICES Workshop on ICES reference points (WKREF1) was tasked to provide a thorough review of the ICES reference points system as a basis to re-evaluate the process for estimating, updating and communicating reference points in the context of the ICES advice. As part of the preparation leading to WKREF1 a large database of the most recent assessment outputs for 78 Category 1 stocks were collated in the form `FLStock` objects, which formed the basis for several components of the presented analyses.
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| 26. |
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| 27. |
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| 28. |
- Casini, Michele, et al.
(författare)
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Changes in population depth distribution and oxygen stratification are involved in the current low condition of the eastern Baltic Sea cod (Gadus morhua)
- 2021
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18, s. 1321-1331
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Tidskriftsartikel (refereegranskat)abstract
- During the past 20 years, hypoxic areas have expanded rapidly in the Baltic Sea, which has become one of the largest marine "dead zones" in the world. At the same time, the most important commercial fish population of the region, the eastern Baltic cod, has experienced a drastic reduction in mean body condition, but the processes behind the relation between deoxygenation and condition remain elusive. Here we use extensive long-term monitoring data on cod biology and distribution as well as on hydrological variations to investigate the processes that relate deoxygenation and cod condition during the autumn season. Our results show that the depth distribution of cod has increased during the past 4 decades at the same time of the expansion, and shallowing, of waters with oxygen concentrations detrimental to cod performance. This has resulted in a progressively increasing spatial overlap between the cod population and low-oxygenated waters after the mid-1990s. This spatial overlap and the actual oxygen concentration experienced by cod therein statistically explained a large proportion of the changes in cod condition over the years. These results complement previous analyses on fish otolith microchemistry that also revealed that since the mid-1990s, cod individuals with low condition were exposed to low-oxygen waters during their life. This study helps to shed light on the processes that have led to a decline of the eastern Baltic cod body condition, which can aid the management of this population currently in distress. Further studies should focus on understanding why the cod population has moved to deeper waters in autumn and on analyzing the overlap with low-oxygen waters in other seasons to quantify the potential effects of the variations in physical properties on cod biology throughout the year.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Casini, Michele, et al.
(författare)
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Skrubbskäddan stjäl östersjötorskens middag
- 2019
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Ingår i: Havsutsikt. - 1104-0513. ; , s. 22-23
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- På Östersjöns botten lever torsk och skrubbskädda, två fiskarter som är viktiga både för ekosystemet och för fisket. Under de senaste fyrtio åren har de båda arternas geografiska utbredning förändrats markant. Idag är torskbeståndet till stor del koncentrerat till i ett mindre område i södra Östersjön där det också finns mängder av skrubbskädda. Den ökade konkurrensen kan ha bidragit till att torsken blivit mycket magrare på senare tid.
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| 33. |
- Casini, Michele, et al.
(författare)
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Spatio-temporal dynamics and behavioural ecology of a "demersal" fish population as detected using research survey pelagic trawl catches: the Eastern Baltic Sea cod (Gadus morhua)
- 2019
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 76, s. 1591-1600
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Tidskriftsartikel (refereegranskat)abstract
- Cod is usually monitored for scientific purposes using bottom trawl surveys, although its regular pelagic occurrence is well documented. Here we analysed, using Generalized Additive Models, the spatio-temporal changes in the Eastern Baltic cod adult population using pelagic catches from an acoustic survey covering 37 years and the whole central Baltic Sea. Our analysis shows that in the northern areas cod catch per unit effort (CPUE, kg h(-1)) was high in the early 1980s whereas it dropped and remained very low thereafter. Conversely, in the southernmost area CPUE largely oscillated after the early 1990s. Our model was able to capture key ecological features of the Baltic cod such as preferred depth of occurrence and response to hypoxic conditions. The model also revealed a clear daily cycle of CPUEs, indicating diel vertical migrations at the population level. The temporal trends of pelagic CPUEs generally followed those from the bottom trawl surveys, although differences were observed especially in the recent years with a relative decline in the cod occurring in the pelagic waters. Our results point to the great potential of acoustic survey trawl catches to complement bottom trawl surveys for investigating the spatio-temporal population dynamics and behaviour of the Baltic cod.
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| 34. |
- Griffiths, Christopher, et al.
(författare)
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Including older fish in fisheries management: A new age-based indicator and reference point for exploited fish stocks
- 2024
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Ingår i: Fish and Fisheries. - 1467-2960 .- 1467-2979. ; 25, s. 18-37
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Tidskriftsartikel (refereegranskat)abstract
- Larger and older fish contribute disproportionately to spawning and play an important role in the replenishment of exploited stocks. Fishing often removes specific size- and age-classes, with direct impacts on stock productivity and population resilience. Despite this, fisheries advice is commonly based on estimates of spawning stock biomass (SSB) and fishing mortality (F) and makes little reference to the importance of size and/or age structure. Consequently, there is a need for indicators of size and/or age structure to better inform fisheries management and help assess global sustainability goals. Here, we introduce a new age-based indicator ABI(MSY) that monitors age structure relative to the equilibrium age structure at F-MSY. We apply this new indicator to 72 commercially important stocks in the Northeast Atlantic, covering 26 species, which collectively contributed 86% of all commercial catches in the region in 2019. We estimate that 62% (45 stocks) currently have proportionally fewer older fish relative to F-MSY conditions, whereas 38% (27 stocks) have proportionally more older fish; we also note patterns with respect to geographic area and taxonomic family. Simulation testing demonstrated that ABI(MSY) is responsive to overfishing and generally tracks (with high sensitivity and specificity) a common measure of stock depletion, SSB relative to B-MSY. Throughout, we show that ABI(MSY) provides information on the age structure of exploited stocks that is complementary to conventional reference points for SSB and F. Further, the framework used to estimate ABI(MSY )make it well placed for integration into current advisory frameworks on fisheries management.
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| 35. |
- Haase, Kevin, et al.
(författare)
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Diet of dominant demersal fish species in the Baltic Sea: Is flounder stealing benthic food from cod?
- 2020
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 645, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge about ecological interactions between species is of paramount importance in ecology and ecosystem-based fisheries management. To understand species interactions, studies of feeding habits are required. In the Baltic Sea, there is good knowledge of the diet of cod, but little is known about the diet of flounder, the second most abundant demersal fish in the region. In this study, we investigated the diets of cod and flounder for the first time using stomach content data collected simultaneously in 2015-2017 over a large offshore area of the southern Baltic Sea. The diet of flounder was relatively constant between sizes and seasons and was dominated by benthos, with a high proportion in weight of the benthic isopod Saduria entomon. The diet of cod differed between seasons and showed an ontogenetic shift with a relative decrease of benthic prey and an increase of fish prey with size. Historic diet data of cod were used to explore cod diet changes over time, revealing a shift from a specialized to generalist feeding mode paralleled by a large relative decline in benthic prey, especially S. entomon. Flounder populations have increased in the past 2 decades in the study area, and therefore we hypothesized that flounder have deprived cod of important benthic resources through competition. This competition could be exacerbated by the low benthic prey productivity due to increased hypoxia, which could contribute to explaining the current poor status of the Eastern Baltic cod. The results of this study point to the importance of including flounder in multispecies end ecosystem models.
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| 36. |
- Hilvarsson, Annelie, et al.
(författare)
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Historical growth of Eastern Baltic cod (Gadus morhua): Setting a baseline with international tagging data
- 2020
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the growth of commercially exploited fish is crucial in fisheries biology and correct estimations of growth and its change over time are paramount for the evaluation of stock status development.Mark-recapture experiments represent a reliable method to estimate growth when age determination based on otolith reading is uncertain, as is the case of the Eastern Baltic cod stock. In this study, historical data (1955-1970) from tagging experiments on Eastern Baltic cod performed by Sweden, Poland, Denmark, Latvia and Germany were digitised and collated for the first time in a unique dataset to estimate historical von Bertalanffy growth function (VBGF) parameters based on fish length increments using GROTAG model.The estimated VBGF parameters were L-infinity = 98.22 cm and k = 0.14 for the period 1955-1964 (n = 1151), L-infinity = 123.61 cm and k = 0.09 for 1965-1970 (n = 2612), and L-infinity = 125.60 cm and k = 0.09 for the aggregated period (n = 3763). A seasonal growth signal was detected for all the periods, with a peak after the spawning season in early autumn. These estimates are the most thorough historical growth baseline now available for the Eastern Baltic cod and can be compared to ongoing and future tagging experiments contributing to the development of stock assessment models for this stock.
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| 37. |
- Kininmonth, Stuart, et al.
(författare)
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Is Diversity the Missing Link in Coastal Fisheries Management?
- 2022
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Ingår i: Diversity. - : MDPI AG. - 1424-2818. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- Fisheries management has historically focused on the population elasticity of target fish based primarily on demographic modeling, with the key assumptions of stability in environmental conditions and static trophic relationships. The predictive capacity of this fisheries framework is poor, especially in closed systems where the benthic diversity and boundary effects are important and the stock levels are low. Here, we present a probabilistic model that couples key fish populations with a complex suite of trophic, environmental, and geomorphological factors. Using 41 years of observations we model the changes in eastern Baltic cod (Gadus morhua), herring (Clupea harengus), and Baltic sprat (Sprattus sprattus balticus) for the Baltic Sea within a Bayesian network. The model predictions are spatially explicit and show the changes of the central Baltic Sea from cod- to sprat-dominated ecology over the 41 years. This also highlights how the years 2004 to 2014 deviate in terms of the typical cod–environment relationship, with environmental factors such as salinity being less influential on cod population abundance than in previous periods. The role of macrozoobenthos abundance, biotopic rugosity, and flatfish biomass showed an increased influence in predicting cod biomass in the last decade of the study. Fisheries management that is able to accommodate shifting ecological and environmental conditions relevant to biotopic information will be more effective and realistic. Non-stationary modelling for all of the homogeneous biotope regions, while acknowledging that each has a specific ecology relevant to understanding the fish population dynamics, is essential for fisheries science and sustainable management of fish stocks.
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| 38. |
- Kraufvelin, Patrik, et al.
(författare)
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Essential coastal habitats for fish in the Baltic Sea
- 2018
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 204, s. 14-30
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Forskningsöversikt (refereegranskat)abstract
- Many coastal and offshore fish species are highly dependent on specific habitat types for population maintenance. In the Baltic Sea, shallow productive habitats in the coastal zone such as wetlands, vegetated flads/lagoons and sheltered bays as well as more exposed rocky and sandy areas are utilized by fish across many life history stages including spawning, juvenile development, feeding and migration. Although there is general consensus about the critical importance of these essential fish habitats (EFH) for fish production along the coast, direct quantitative evidence for their specific roles in population growth and maintenance is still scarce. Nevertheless, for some coastal species, indirect evidence exists, and in many cases, sufficient data are also available to carry out further quantitative analyses. As coastal EFH in the Baltic Sea are often found in areas that are highly utilized and valued by humans, they are subjected to many different pressures. While cumulative pressures, such as eutrophication, coastal construction and development, climate change, invasive species and fisheries, impact fish in coastal areas, the conservation coverage for EFH in these areas remains poor. This is mainly due to the fact that historically, fisheries management and nature conservation are not integrated neither in research nor in management in Baltic Sea countries. Setting joint objectives for fisheries management and nature conservation would hence be pivotal for improved protection of EFH in the Baltic Sea. To properly inform management, improvements in the development of monitoring strategies and mapping methodology for EFH are also needed. Stronger international cooperation between Baltic Sea states will facilitate improved management outcomes across ecologically arbitrary boundaries. This is especially important for successful implementation of international agreements and legislative directives such as the Baltic Sea Action Plan, the Marine Strategy Framework Directive, the Habitats Directive, and the Maritime Spatial Planning Directive, but also for improving the communication of information related to coastal EFH among researchers, stakeholders, managers and decision makers. In this paper, efforts are made to characterize coastal EFH in the Baltic Sea, their importance and the threats/pressures they face, as well as their current conservation status, while highlighting knowledge gaps and outlining perspectives for future work in an ecosystem-based management framework. (C) 2018 Elsevier Ltd. All rights reserved.
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| 39. |
- Larsson, Stefan, et al.
(författare)
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Indikatorrapportering för “Hållbart nyttjande av fisk- och skaldjursbestånd i kust och hav” : bedömningsåret 2022
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Sedan 2018 har institutionen för akvatiska resurser (SLU Aqua), på uppdrag av Havs- och vattenmyndigheten, utformat en indikator med tillhörande för uppföljning av miljökvalitetsmålet ”Hav i balans samt levande kust och skärgård”. Indikatorn (Hållbart nyttjande av fisk- och skaldjursbestånd i kust och hav) fokuserar på en övergripande status för svenska fisk- och skaldjursbestånd längs kusterna och i haven. Bedömningen baseras på årliga analyser av enskilda fiskbestånds status i rapporten ”Fisk- och skaldjursbestånd i hav och sötvatten”, och anger om bestånden fiskas hållbart eller och ej. Bedömningar för indikatorn har utförts mellan åren 2015- 2022.I föreliggande rapport presenteras en bedömning av indikatorns status för året 2022. Eftersom bedömningarna av nationellt förvaltade fisk- och skaldjursbestånd under 2022 uppdaterats jämfört med tidigare år, innehåller denna rapport två bedömningar. Den ena utgår från den nya modifierade bedömningsmetodiken, och den andra som följer den äldre metodiken och därmed medger en jämförelse av indikatorns status över tid.Av de totalt 72 redovisade bestånden i rapporten "Fisk- och skaldjursbestånd i hav och sötvatten 2022” kunde en bedömning göras för 68 bestånd. Av dessa klassades 35 (48,6 %) som ”hållbart nyttjande”. Indikatorns status var högst i Bottenviken (62,5 % av bestånden klassades som ”hållbart nyttjande”), följt av Västerhavet (52,5 %), och Östersjön (43,5 %). Lägst andel bedömda bestånd klassade som ”hållbart nyttjande” fanns i Bottenhavet (36,4 %). En högre andel bestånd med så kallad analytisk beståndsuppskattning (MSY- konceptet) ger en högre tillförlitlighet i den sammantagna bedömningen av de bestånd som redovisas i indikatorn. Tillförlitligheten för klassningen 2022 är högst i Västerhavet där andelen bestånd bedömda enligt MSY- konceptet är 35%, följt av Östersjön (25%), Bottenhavet (17%) och Bottenviken (11%). Andelen av de totala officiella svenska kommersiella landningarna av fisk och skaldjur som indikatorn omfattar ligger över 99 %. Med utgångspunkt i den äldre metodiken har andelen hållbara bestånd sjunkit något under 2022 jämfört med 2021 (från 52,2 % 2021 till 48,6 % 2022), detta då antalet redovisade bestånd ökat från 69 till 72.I en jämförelse mellan bedömningarna baserade på den äldre och den nya modifierade bedömningsmetodiken ses endast små skillnader i indikatorns status. Antalet och andelen bestånd kategoriserade som ”hållbart nyttjande” under bedömningsåret 2022 var de samma för båda metoderna (35 st, 48,6%). Med den nya metoden kunde emellertid ett bestånd mer bedömas jämfört med den gamla metoden.
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| 40. |
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| 41. |
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| 42. |
- Mion, Monica, et al.
(författare)
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Otolith sectioning reveals higher maximum age in greater weever (Trachinus draco)
- 2024
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Ingår i: Journal of Fish Biology. - 0022-1112 .- 1095-8649. ; 104, s. 1619-1622
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Tidskriftsartikel (refereegranskat)abstract
- Growth and maximum age are two key parameters that inform resilience of fish populations to exploitation. Existing information on those for greater weever inhabiting the eastern North Sea is based on the analysis of whole otoliths. Here, we present a reanalysis using sectioned otoliths. The results reveal a different growth pattern and a higher maximum age than that previously reported. The higher maximum age makes greater weever populations more vulnerable to exploitation. Such information can serve as a basis for the estimation of the growth curve that can be used for future assessment of the species.
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| 43. |
- Neuenfeldt, Stefan, et al.
(författare)
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Feeding and growth of Atlantic cod (Gadus morhua L.) in the eastern Baltic Sea under environmental change
- 2020
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 77:2, s. 624-632
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Tidskriftsartikel (refereegranskat)abstract
- Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea. We show a recent reversal in feeding level over body length. Present feeding levels of small cod indicate severe growth limitation and increased starvation-related mortality. For young cod, the low growth rate and the high mortality rate are manifested through a reduction in size-at-age. The low feeding levels are likely the result of a decrease in benthic prey abundance due to increased hypoxic areas, while decreasing abundances of pelagic species in the area of cod distribution have prevented a compensatory shift in diet. Our study emphasizes that environmental forcing and the decline in pelagic prey caused changes in consumption and growth rates of small cod. The food reduction is amplified by stunted growth leading to high densities of cod of smaller size competing for the scarce resources. The average growth rate is negative, and only individuals with feeding levels well above average will survive, though growing slowly. These results suggest that the relation between consumption rate, somatic growth and predatorprey population densities is strongly environmentally mediated.
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| 44. |
- Niiranen, Susa, et al.
(författare)
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Predator−prey body size relationships of cod in a low-diversity marine system
- 2019
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 627, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- How predators select their prey largely defines ecosystem trophic structure, function and dynamics. In aquatic systems, organism body size is an important trait explaining predator− prey interactions. Here, we used a unique Atlantic cod Gadus morhua stomach content dataset with diet information from over 100 000 individuals collected from the Baltic Sea in 1963−2014, to explore prey size distribution and predator−prey mass ratios in the diet of Eastern Baltic cod. Maximum and average prey sizes increased with predator size, as for cod in other systems. However, the prey size spectra found in Eastern Baltic cod stomachs reflect the low species diversity in the Baltic Sea. In general, Eastern Baltic cod feed on smaller prey in relation to their body size than other cod populations. Due to the truncated prey size distribution in the Baltic Sea, cod cannibalism functions as a compensatory mechanism that allows Baltic cod to reach their prey size potential. On the other hand, small- and intermediate-sized cod prey mainly on a few invertebrate prey species, potentially making them vulnerable to changes in these prey populations. Our results encourage further studies disentangling the relative effects of prey preference and prey availability on cod trophodynamics in species-poor systems such as the Baltic Sea.
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| 45. |
- Orio, Alessandro, et al.
(författare)
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A three-dimensional view on biodiversity changes: spatial, temporal, and functional perspectives on fish communities in the Baltic Sea
- 2018
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 75, s. 2463-2475
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Tidskriftsartikel (refereegranskat)abstract
- Fisheries and marine ecosystem-based management requires a holistic understanding of the dynamics of fish communities and their responses to changes in environmental conditions. Environmental conditions can simultaneously shape the spatial distribution and the temporal dynamics of a population, which together can trigger changes in the functional structure of communities. Here, we developed a comprehensive framework based on complementary multivariate statistical methodologies to simultaneously investigate the effects of environmental conditions on the spatial, temporal and functional dynamics of species assemblages. The framework is tested using survey data collected during more than 4000 fisheries hauls over the Baltic Sea between 2001 and 2016. The approach revealed the Baltic fish community to be structured into three sub-assemblages along a strong and temporally stable salinity gradient decreasing from West to the East. Additionally, we highlight a mismatch between species and functional richness associated with a lower functional redundancy in the Baltic Proper compared with other sub-areas, suggesting an ecosystem more susceptible to external pressures. Based on a large dataset of community data analysed in an innovative and comprehensive way, we could disentangle the effects of environmental changes on the structure of biotic communities-key information for the management and conservation of ecosystems.
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| 46. |
- Orio, Alessandro
(författare)
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Assessing the vulnerability of Mediterranean demersal stocks and predicting exploitation status of un-assessed stocks
- 2015
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 171, s. 110-121
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Tidskriftsartikel (refereegranskat)abstract
- According to the Common Fisheries Policy, all commercial fish stocks in the Mediterranean and Black Sea should be managed at MSY by 2015-2020. However, currently 95% of assessed stocks are overexploited and 73% of demersal species are not assessed. To explore the risk of overexploitation to un-assessed stocks, vulnerability scores were constructed using Productivity Susceptibility Analysis (PSA) for 151 Mediterranean demersal fish species. Out of 151 species, 58 displayed low vulnerability, 20 medium vulnerability, 25 high vulnerability and 48 were considered of major concern. More than half of stocks showed a risk of being overfished (termed "vulnerability"), greater than that of the stocks currently assessed in the Mediterranean Sea. Most of the cartilagineous fish fell into the high and major concern areas. The quality of data used for the PSA was scored and these scores could be used to improve future collection of data. Vulnerability scores are well correlated with IUCN red list classification. To rank the priority of commercial stocks still to be assessed, vulnerability scores were scaled with landings and mean price per stock. Eight of the top fifteen ranking stocks are currently not assessed. When the vulnerability of cartilaginous fish was tested against rate of decline estimated from trawl survey time-series, no strong correlation was found. The exploitation ratio (F/F-msy) of assessed stocks was regressed, using generalized mixed models, against PSA scores and area and a significant relationship was found. Using this result, assessed stocks were used as a training set to predict the exploitation of un-assessed stocks. F/F-msy was predicted for 151 species in 14 management areas (GSAs). The results over all areas is that 39 speciesarea combinations are exploited sustainably, all occurring in area 20 (Greece), while the remaining 2075 are exploited unsustainably with respect to F-msy (F/F-msy > 1). This prediction model, albeit after further refinement with more data and testing, could be used to predict exploitation ratio when no information on stock status is available. We predict that approximate to 98% of the unassessed demersal fish species are potentially overexploited in the evaluated areas. This makes it clear that strong management action will be required to achieve the targets of the Common Fisheries Policy in the next 1-5 years. (C) 2015 Elsevier B.V. All rights reserved.
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| 47. |
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| 48. |
- Orio, Alessandro, et al.
(författare)
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Characterizing and predicting the distribution of Baltic Sea flounder (Platichthys flesus) during the spawning season
- 2017
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Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101 .- 1873-1414. ; 126, s. 46-55
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Tidskriftsartikel (refereegranskat)abstract
- Identification of essential fish habitats (EFH), such as spawning habitats, is important for nature conservation, sustainable fisheries management and marine spatial planning. Two sympatric flounder (Platichthys flesus) ecotypes are present in the Baltic Sea, pelagic and demersal spawning flounder, both displaying ecological and physiological adaptations to the low-salinity environment of this young inland sea. In this study we have addressed three main research questions: 1) What environmental conditions characterize the spatial distribution and abundance of adult flounder during the spawning season? 2) What are the main factors defining the habitats of the two flounder ecotypes during the spawning season? 3) Where are the potential spawning areas of flounder? We modelled catch per unit of effort (CPUE) of flounder from gillnet surveys conducted over the southern and central Baltic Sea in the spring of 2014 and 2015 using generalized additive models. A general model included all the stations fished during the survey while two other models, one for the demersal and one for the pelagic spawning flounder, included only the stations where each flounder ecotype should dominate. The general model captured distinct ecotype-specific signals as it identified dual salinity and water depth responses. The model for the demersal spawning flounder revealed a negative relation with the abundance of round goby (Neogobius melanostomus) and a positive relation with Secchi depth and cod abundance. Vegetation and substrate did not play an important role in the choice of habitat for the demersal ecotype. The model for the pelagic spawning flounder showed a negative relation with temperature and bottom current and a positive relation with salinity. Spatial predictions of potential spawning areas of flounder showed a decrease in habitat availability for the pelagic spawning flounder over the last 20 years in the central part of the Baltic Sea, which may explain part of the observed changes in populations' biomass. We conclude that spatiotemporal modelling of habitat availability can improve our understanding of fish stock dynamics and may provide necessary biological knowledge for the development of marine spatial plans.
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| 49. |
- Orio, Alessandro
(författare)
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Counting stars: contribution of early career scientists to marine and fisheries sciences
- 2022
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 79, s. 2351-2361
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Tidskriftsartikel (refereegranskat)abstract
- Scientific careers and publishing have radically changed in recent decades creating an increasingly competitive environment for early career scientists (ECS). The lack of quantitative data available on ECS in marine and fisheries sciences prevents direct assessment of the consequences of increased competitiveness. We assessed the contributions of ECS (up to 6 years post first publication) to the field using an indirect approach by investigating the authorships of peer-reviewed articles. We analysed 118461 papers published by 184561 authors in the top 20 marine and fisheries sciences journals over the years 1991–2020. We identified a positive long-term trend in the proportion of scientific articles (co-)authored by ECS. This suggests a growing contribution by ECS to publications in the field. However, the mean proportion of ECS (co-)authors within one publication declined significantly over the study period. Subsequent tests demonstrated that articles with ECS (co-)authors receive fewer citations and that the proportion of ECS (co-)authors on an article has a significant negative effect on the number of citations. We discuss the potential causes of these inequalities and urge systematic support to ECS to achieve more balanced opportunities for funding and publishing between ECS and senior scientists.
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| 50. |
- Orio, Alessandro, et al.
(författare)
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Deoxygenation impacts on Baltic Sea cod: Dramatic declines in ecosystem services of an iconic keystone predator
- 2022
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Ingår i: AMBIO: A Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51, s. 626-637
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Tidskriftsartikel (refereegranskat)abstract
- The intensified expansion of the Baltic Sea's hypoxic zone has been proposed as one reason for the current poor status of cod (Gadus morhua) in the Baltic Sea, with repercussions throughout the food web and on ecosystem services. We examined the links between increased hypoxic areas and the decline in maximum length of Baltic cod, a demographic proxy for services generation. We analysed the effect of different predictors on maximum length of Baltic cod during 1978-2014 using a generalized additive model. The extent of minimally suitable areas for cod (oxygen concentration >= 1 ml l(-1)) is the most important predictor of decreased cod maximum length. We also show, with simulations, the potential for Baltic cod to increase its maximum length if hypoxic areal extent is reduced to levels comparable to the beginning of the 1990s. We discuss our findings in relation to ecosystem services affected by the decrease of cod maximum length.
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