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The short term impacts of fishing pressure were compared with the variability induced by environmental drivers on quantitative benthic community impact indicators. The different pressures were evaluated through comparative multifactor statistical analyses of their effects on macrofauna indicators in a Baltic Sea area with high natural disturbance. The area is exposed to a wide range of fishing intensities from long term non-fished areas to seasonal and annually frequently fished areas. Such evaluations are important for comparing the influence and short term variability of impact indicators from both demersal fisheries and the environment, including benthic community biodiversity (species richness), density (abundance in number of individuals), biomass, and average individual mean weight, with high spatio-temporal resolution. Environmental drivers include near bottom water current speed, salinity, temperature, and dissolved oxygen concentration, considering habitat specific and seasonal conditions. Demersal fishing-induced impacts were evident for all indicators. The highest fishing impacts were estimated in soft muddy and sandy habitats and in the second quarter of the year for all indicators, considering complex interactions. All environmental drivers, especially, current speed, had significant impacts on all indicators. The significant influences and short term variability caused by environmental drivers were of the same or larger order of magnitude as fishing impacts. Consequently, the short term influence of environmental drivers and seasonal differences in fishing pressure need to be considered when using quantitative benthic fishing impact indicators and identifying areas that are more or less resilient to fishing in relation to short- and long-term fisheries management plans.

The implementation of ecosystem-based fisheries management requires knowledge on the ecological impact of fishing activities on species and their habitats – those both targeted and not targeted by fisheries. To identify whichecological impacts are key and what is known about them, SEAwise consulted stakeholders through European Advisory Councils and conducted a systematic review of the scientific literature to map the available knowledge and evidence. Specific reference was given to the bycatch of Protected, Endangered and Threatened (PET) species, benthic habitats, food webs and biodiversity, and impact from fisheries-related litter and ghost nets. At the stakeholder consultations, sharks and/or elasmobranchs, turtles, species interactions, and seals or marine mammals were identified as top ranked in at least three out of the five regions. Other terms identified by at least two Case Study regions were: seabirds, sensitive species, benthic habitats, litter, PET species, invasive species and species interactions.Relevant data were extracted from 549 retained papers. The majority of studies were conducted in the Mediterranean Sea, whereas only few papers reported on fishing impacts in the Baltic Sea (see figure below). Bony fish (teleosts) and benthos were the most studied ecosystem components in all Case Study regions, whereas marine mammals and cartilaginous fish were often studied in relation to bycatch of PET species. Out of the 549 papers, most of them were related to fishing impacts on food webs and biodiversity and benthic habitats, followed bybycatch of PET species and other fishing impact studies (not related to any task). Fewest studies were related to the impact of fisheries-related litter and ghost nets. Demersal trawls were by far the most studied gear in studies on commercial fishing impacts. For recreational fisheries, hooks and lines, in particular angling, was the most studied fishing activity. Among the items identified by the stakeholders, marine ma

The Marine Strategy Framework Directive (MSFD) requires Member States to achieve good environmental status (GES) across their marine waters. The EU have requested ICES to advise on methods for assessing adverse effects on seabed habitats, through selection of relevant indicators for the assessment of benthic habitats and seafloor integrity and associated threshold values for GES in relation to Descriptor 6 – Seabed integrity under the MFSD. Two sets of criteria were developed to evaluate indicators and thresholds respectively for evaluation of suitability for assessing GES. 16 indicator and 12 threshold criteria were compiled and weighted by importance. The criteria were designed for evaluation at a subregional or regional level. The scoring for these criteria is meant as a guidance when choosing indicators and thresholds, so failure to meet one criterion will not necessarily prevent the use of the indicator or threshold in an assessment. The framework was evaluated for 6 indicators and for 11 methods for setting thresholds. The criteria were found to be useful for evaluation both indicators and thresholds. The process works most consistently when there are experts in the group on both the criteria themselves and on the indicators and thresholds. The MFSD Descriptor 6 determination of GES needs both a quality threshold (when are seabed habitats in a good state in a specific location) and an extent threshold (proportion of the assessment area that needs to have seabed habitats in good state). Eleven different methods for setting thresholds were identified, of which more are suitable for setting quality than for extent thresholds. Preferred methods identified an ecologically-motivated difference between a good and degraded state, rather than another transition. Quality thresholds based on the lower boundary of the range of natural variation were considered most promising. This approach can be used for most, but not all, indicators. The WK co

Objectives, effort, and deliverables The primary project objectives and outcomes are organized within three overarching components, which have also formed the backbone of the work packages and associated tasks of the project. Fishing footprint: i) Development of a new methodology to estimate the exact spatial extent and gear footprint of Danish anchor seines. ii) The development of a hierarchical method that combines different sources of fisheries monitoring data (VMS, AIS, and Black Box data) to produce high-precision fishing pressure maps (grid cell resolution of 100x100m) of Danish demersal fisheries. Gear specific depletion rates: i) Development of a new methodology that theoretically derives gear-specific depletion rates, based on gear design and component-specific penetration depths, for ten different commercial fishing gears. ii) Quantification of the benthic impact (benthic fauna depletion) of the Danish Seine fishing gear based on in-project sea trials and experimental data. iii) Quantification of the impact on the benthic fauna community from a standard and a modified sandeel otter trawl based on experimental data from sea trials previously conducted by DTU Aqua. iv) Quantification of the impact on the benthic fauna community from a light-weight mussel dredge based on experimental data from sea trials previously conducted by DTU Aqua. Fishery specific assessment of benthic impact: i) Development of a new methodology to assess the amount of sediment mobilized by demersal fishing gears, based on the spatial distribution of both fishing activity and fine sediments, combined with gear-specific drag coefficients. ii) Integration of project results and external science-based methods and results into a framework, tailored to assess the benthic impact from the different Danish fisheries with Mobile Bottom Contacting Gears (MBCGs) on sandbanks in the North Sea, and applied to

Background: West coast of Denmark used to be an important fishing area in previous decades. Fishers in the area have reported declines in local fish populations and fishing vessels have been reduced in numbers. Fishing is taking place further North, in Skagerrak, or further offshore. Such observations were also confirmed by previous scientific projects in the area. Nevertheless, stocks in the North Sea have been rebuilding and there is a question if the coastal areas will also see an increase in population sizes of important commercial species. Aims of the project: Given the situation in the area, the Vesterhavsfisk project has as a main goal to investigate important species distribution changes and evaluate potential fishing opportunities in the area. The aims of the project are to i) collate existing knowledge from previous studies in the area, ii) gather new information from 2 scientific surveys along 3 transects off the Danish west coast and one transect in Skagerrak, iii) recruit commercial fishers to conduct experimental fishing using commercial style gillnets along the same transects, iv) collect stomach contents from plaice and benthic samples to investigate feeding preferences of the species along the different transects and, v) evaluate the potential of re-establishing the area as commercially and biologically sustainable fishing grounds. Results: Commercial species were caught during the Havfisken survey, but the sizes indicate that the coastal area is mostly used by juvenile populations that are not interesting commercially. The number of fish caught during the gillnet experimental fishing were too low confirming that the area is not a viable fishing area. Stomach and benthic analyses for plaice showed differences in the feeding behaviour of the species and the faunal biodiversity from North to South. Changes in environmental conditions, like increasing temperatures closer to the shore have caused important commerci

Dredging for wild mussels Mytilus edulis Linnaeus, 1758 takes place in the marine protected areas (Natura 2000 sites) in Denmark. The fishery is strictly regulated to limit the impact of dredging to the benthic environment, and requires the use of modified lightweight mussel dredges. Nevertheless, the depletion of the benthic macrofauna associated with M. edulis beds after impact from such dredges is yet to be quantified. Here, dredging is shown to result in a significant decline in the density, species richness, and biological traits directly in the dredge track but no significant impact on the community composition. Species richness remained significantly affected 4 mo post dredging, although the positive trend after 4 mo may signal recovery. An effect of dredging was also detected in areas adjacent (approximately 5 m) to the dredge tracks, but needs further investigation to understand this impact. The results provide an estimate of benthic macrofaunal depletion in the dredge track as well as of the short-term recovery, which may be of use in the management of the fishery. Finally, it is suggested that species richness may be a more sensitive indicator than density in a eutrophic and species-poor system.

Conflicts of interests between economic and nature conservation stakeholders are increasingly common in coastal seas, inducing a growing need for evidence-based marine spatial planning. This requires accurate, high-resolution habitat maps showing the spatial distribution of benthic assemblages and enabling intersections of habitats and anthropogenic activities. However, such detailed maps are often not available because relevant biological data are scarce or poorly integrated. Instead, physiotope maps, solely based on abiotic variables, are now often used in marine spatial planning. Here, we investigated how pointwise, relatively sparse biological data can be integrated with gridded, high-resolution environmental data into informative habitat maps, using the intensively used southern North Sea as a case-study. We first conducted hierarchical clustering to identify discrete biological assemblages for three faunal groups: demersal fish, epifauna, and endobenthos. Using Random Forest models with high-resolution abiotic predictors, we then interpolated the distribution of these assemblages to high resolution grids. Finally, we quantified different anthropogenic pressures for each habitat. Habitat maps comprised a different number of habitats between faunal groups (6, 13, and 10 for demersal fish, epifauna, and endobenthos respectively) but showed similar spatial patterns for each group. Several of these ‘fauna-inclusive’ habitats resembled physiotopes, but substantial differences were also observed, especially when few (6; demersal fish) or most (13; epifauna) physiotopes were delineated. Demersal fishing and offshore wind farms (OWFs) were clearly associated with specific habitats, resulting in unequal anthropogenic pressure between different habitats. Natura-2000 areas were not specifically associated with demersal fishing, but OWFs were situated mostly inside these protected areas. We thus conclude that habitat maps derived from biological datasets that cover rele, Aircraft Noise and Climate Effects

Bottom trawling results in widespread impacts to the structure and composition of benthic communities. Although an ecosystem approach to fisheries management aims to conserve marine biodiversity and ecosystem function, there remains a lack of empirical evidence regarding the effects of trawling on benthic functional properties. Here, we examined the sensitivity of benthic macrofauna communities to trawling using their biological traits, and compared trait responses across size-categories and survey types. We collected 84 benthic soft-sediment samples by Van Veen grab (0.1 m2) in the Kattegat in 2016, and complemented with 827 Haps cores (0.0143 m2) gathered over a long-term monitoring programme between 2006 and 2013. By analysing trait response in 3 size categories (small: 1-4 mm fraction; large: ≥4 mm fraction; full community: all individuals combined), we demonstrate a size-dependent effect of trawling on benthic trait composition, where the traits of large-bodied fauna (≥4 mm) were more sensitive. Specifically, larger sessile, deep-living, suspension-feeding, tube-dwelling, subsurface deposit-feeding, burrow-dwelling, and long-lived (≥10 yr) individuals were among the most affected. Our results based on large fauna were largely in agreement with trait responses observed in the multi-year monitoring data, suggesting that trait data gathered from a targeted one-time sampling event can convey information on both acute (short-term) and chronic (long-term) trawling impacts. Given that most trawling impact assessments do not consider size-based effects, we outline how size-separating the community can be used to improve the detectability of trawling impacts, and provide new insights into the functional impacts of fishing on the seabed.

This dataset consists of five zipped folders: Final_habitatmaps_physiotopes.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the final habitat and physiotope maps as presented in the paper. Final_accuracy_plots.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the final habitat accuracy maps as presented in the paper. Input_abiotic_factors.zip: All the abiotic factor data used to determine the relevant environmental gradients in the study area are included as raster data (tif) in ETRS89 UTM31 projection (supplementary figures B1-22). Most datasets were obtained elsewhere, but all datasets were processed by Karin van der Reijden in R and ArcGIS to have a similar projection, resolution and extent. In addition, the shapefiles (in ETRS89 UTM31 projection) of offshore wind farms, Natura2000-areas and national waters are included. Data-description: An overview of all folders, and of all files included in the abiotic factors folder. Input_environmental_gradients.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the environmental gradients used in the study as input to the Random Forest models and physiotope-delineation. Each gradient is a PCA-component (1-7) summarizing the abiotic factors. Gradients including (FE) and excluding (NF) demersal fishing intensity as abiotic factor are available. Input_biological_cluster_data.zip: This folder contains datafiles (.Rdata and .CSV files) for the three biological datasets (demersal fish, epifauna, endobenthos), that give locations and corresponding biological cluster, as used in the Random Forest habitat maps. The biological datasets used for the determination of biological clusters are not included in this repository. For demersal fish and endobenthos, these datasets can freely be downloaded at the DATRAS-portal on the ICES website (demersal fish) and the EMODnet Biology portal (endobenthos). Link to demersal fish data: https://datras.ices.dk, This dataset consists of five zipped folders: Final_habitatmaps_physiotopes.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the final habitat and physiotope maps as presented in the paper. Final_accuracy_plots.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the final habitat accuracy maps as presented in the paper. Input_abiotic_factors.zip: All the abiotic factor data used to determine the relevant environmental gradients in the study area are included as raster data (tif) in ETRS89 UTM31 projection (supplementary figures B1-22). Most datasets were obtained elsewhere, but all datasets were processed by Karin van der Reijden in R and ArcGIS to have a similar projection, resolution and extent. In addition, the shapefiles (in ETRS89 UTM31 projection) of offshore wind farms, Natura2000-areas and national waters are included. Data-description: An overview of all folders, and of all files included in the abiotic factors folder. Input_environmental_gradients.zip: This folder contains the raster (tif) files in ETRS89 UTM31 projection of the environmental gradients used in the study as input to the Random Forest models and physiotope-delineation. Each gradient is a PCA-component (1-7) summarizing the abiotic factors. Gradients including (FE) and excluding (NF) demersal fishing intensity as abiotic factor are available. Input_biological_cluster_data.zip: This folder contains datafiles (.Rdata and .CSV files) for the three biological datasets (demersal fish, epifauna, endobenthos), that give locations and corresponding biological cluster, as used in the Random Forest habitat maps. The biological datasets used for the determination of biological clusters are not included in this repository. For demersal fish and endobenthos, these datasets can freely be downloaded at the DATRAS-portal on the ICES website (demersal fish) and the EMODnet Biology portal (endobenthos). Link to demersal fish data: https://datras.ices.dk

The round goby (Neogobius melanostomus) was first observed in the Baltic Sea in 1990 and has since displayed substantial secondary dispersal, establishing numerous dense populations where they may out compete native fish and negatively impact prey species. There have been multiple round goby diet studies from both the Baltic Sea and the North American Great Lakes where they are similarly invasive. However, studies that quantify their effects on recipient ecosystems and, specifically, their impacts on the benthic invertebrate macrofauna are rare, particularly from European waters. In this study, we conducted the first before-after study of the potential effects of round goby on benthic invertebrate macrofauna taxa in marine-brackish habitats in Europe, focusing of two sites in the Western Baltic Sea, Denmark. Results were in line with those from the Great Lakes, indicating negative impacts on specific molluscan taxa (e.g. Cardiidae bivalves and Neritidae gastropods, which both showed a fall in detected densities of approximately 98% within the Guldborgsund Strait). In contrast, many other groups appeared to be largely unaffected or even show positive trends following invasion. Round goby gut content data were available at one of our study sites from the period immediately after the invasion. These data confirmed that round goby had in fact been preying on the subset of taxa displaying negative trends.

Conflicts of interests between economic and nature conservation stakeholders are increasingly common in coastal seas, inducing a growing need for evidence-based marine spatial planning. This requires accurate, high-resolution habitat maps showing the spatial distribution of benthic assemblages and enabling intersections of habitats and anthropogenic activities. However, such detailed maps are often not available because relevant biological data are scarce or poorly integrated. Instead, physiotope maps, solely based on abiotic variables, are now often used in marine spatial planning. Here, we investigated how pointwise, relatively sparse biological data can be integrated with gridded, high-resolution environmental data into informative habitat maps, using the intensively used southern North Sea as a case-study. We first conducted hierarchical clustering to identify discrete biological assemblages for three faunal groups: demersal fish, epifauna, and endobenthos. Using Random Forest models with high-resolution abiotic predictors, we then interpolated the distribution of these assemblages to high resolution grids. Finally, we quantified different anthropogenic pressures for each habitat. Habitat maps comprised a different number of habitats between faunal groups (6, 13, and 10 for demersal fish, epifauna, and endobenthos respectively) but showed similar spatial patterns for each group. Several of these ‘fauna-inclusive’ habitats resembled physiotopes, but substantial differences were also observed, especially when few (6; demersal fish) or most (13; epifauna) physiotopes were delineated. Demersal fishing and offshore wind farms (OWFs) were clearly associated with specific habitats, resulting in unequal anthropogenic pressure between different habitats. Natura-2000 areas were not specifically associated with demersal fishing, but OWFs were situated mostly inside these protected areas. We thus conclude that habitat maps derived from biological datasets that cover relevan

Bottom trawling alters the abundance, diversity, size-composition, and function of benthic communities. However, the ability to detect these impacts over large spatial scales can be obscured by various complicating factors, such as community adaptation to disturbance and co-varying environmental conditions. An ecosystem-based approach to fisheries management therefore requires ecological indicators which can ‘disentangle’ trawling effects from other natural and human drivers, and respond effectively to shifts in ecological quality. We collected benthic macrofaunal samples at 21 sites across a Norway lobster Nephrops norvegicus fishing ground in the Kattegat, and separated the benthic community into small (1–4 mm) and large (>4 mm) size fractions. Four taxonomic indicators (total density, species density, Shannon diversity, and biomass) and four functional indicators (functional diversity, functional richness, functional evenness, and functional dispersion) were calculated based on each size fraction, and the two fractions combined (pooled community). Here, we compare the ability of these indicators to detect trawling impacts across size categories. We show that indicators derived from large macrofauna were highly effective in this regard, and were less influenced by other environmental drivers, such as depth, sediment grain size, bottom current velocity, salinity, and temperature. This suggests that the taxonomic and functional characteristics of benthic communities display a size-dependent sensitivity to trawling disturbance, and therefore community metrics based on large benthic macrofauna may provide useful indicators. By contrast, indicators derived from the small fraction performed poorly, and those based on the pooled community demonstrated a varied ability to detect trawling. Small macrofauna are typically characterised by high density, diversity, and population growth rates, and their relative resilience to trawling may mask the response of the more sensitiv

Under the European Union’s Marine Strategy Framework Directive (MSFD) and Common Fisheries Policy (CFP), management organisations are directed to evaluate measures for reducing the footprint of fishing on the seafloor. We applied a spatial modelling platform to evaluate the effects of spatial fishery management measures on the Baltic Sea. The evaluation includes restricting areas for fishing with the dual goal of reducing the impact on benthic habitats and minimising negative effects on fishery catch and profit. To redistribute the fishing effort realistically, the model simulates individual-vessel agents and behavioural rules. The model integrates benthic community dynamics by combining gear-specific depletion rates from fishing agents with habitat-specific trait-based recovery rates for the benthic communities. Our simulations showed that closing areas in the central Baltic Sea and condensing the fishing efforts into core fishing areas did not improve the relative benthic status (RBS). In addition, the fisheries were adversely affected by reduced fishing opportunities, further impacting their economic performance. The potential for improving the overall RBS with spatial management is dubious in the central Baltic, given that the area is dominated by relatively short-lived and rapidly recovering benthic species. By contrast, the Kattegat showed a substantial improvement in the RBS, as determined by measures combining the protection of long-lived benthic communities with the mitigation of high-impact fisheries. Our results and investigations provide different bio-economic scenarios on benthos and fisheries dynamics resulting from specific management measures. The developed knowledge base and modelling tool is expected to assist policymakers in identifying the most appropriate measures to achieve both a Good Environmental Status (GES) of the seafloor according to the MSFD and to maintain sustainable fisheries and stocks according to the CFP.

As part of a larger project funded by the Danish Environmental Protection Agency (“Effects on the quality elements defined by the EU Water Framework Directive (WFD) of other pressure factors than excess nutrient load and climate change”), fishery with trawl, dredge or other mobile bottom-contacting gear (MBCG) has been identified as a potential risk to all of the quality elements of the WFD (Petersen et al. 2018). In this report, we have analysed effects of fisheries on i) benthic fauna using statistical methods to correlate data on fishing pressure with data on fauna composition and ii) phytoplankton using a 3D dynamic model to show effects of mussel fishery on Chlorophyll a concentration (Chl.a) and iii) cascade effects on phytoplankton and nutrient concentrations in a review study of the literature. For impact on benthic fauna, we have mapped fishing pressure in Danish water bodies using information of vessel activity from VMS (Vessel Monitoring System), AIS (Automatic Identification System) and the BB (Black Box) system. The BB system is used only in the mussel and oyster fishery and monitors vessel position and activity every 10th second, allowing for fishing pressure to be mapped very precisely. The AIS and VMS systems are much less precise as they only record vessel activity once an hour (VMS) or at irregular intervals and vessel coverage (AIS). Slightly less than 50% of the 119 Danish water bodies had fishery with MBCGs in the period 2014-18. Based on data from all three monitoring systems, a map of fishing intensities (Swept Area Ratios [SARs]) in quadrats of 100 x 100 m was produced for all water bodies. In terms of spatial extent (proportion of water body seabed area impacted) fishing pressure was highest along the west coast of Jutland, in Ålbæk Bight, and south of Fyn (Figure 2.1). In the same areas, fishing intensity was also highest, with substantial parts of the seabed in the water bodies being impacted between 1 and 5 ti