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Marine protected areas (MPAs) are widely recognized as an important tool for biodiversity conservation and fisheries management. Despite empirical evidence that abundance and biomass of fished species increase within MPA boundaries, the potential for MPAs to provide fisheries benefits to adjacent waters remains debated. This study documents the first systematic review of empirical evidence for spillover from MPAs in the European Union and other temperate regions. Findings show that scientific evidence of ecological and fishery spillover is relatively sparse. The combination of MPA characteristics (its age, local context and whether it is part of a network) proved capable of predicting the occurrence of spillover and therefore these are key considerations for the design of MPAs. Further, this study confirms that species mobility and reproductive strategies are important traits in explaining occurrence of spillover. There is a wide range of methodological approaches (sampling design, methods, statistical analyses) used in the literature to investigate spillover. Ideally, assessment should be based on a Before After Control Impact design, with a distance gradient sampling scheme integrated over time. A combination of studies, using biological sampling and tagging, gives a more complete picture of potential spillover effects. Using the literature available and study quantitative analyses, a conceptual model tool was developed to estimate the likelihood of spillover for existing and proposed MPAs. The tool integrates the potential social, ecological and economic factors that may lead to MPA spillover. Finally, qualitative and quantitative approaches were used to evaluate ecological and/or fishery spillover effects for 15 case studies from across Europe. The case studies demonstrate that MPAs can lead to increased species spillover, but these patterns are species-specific, and spillover effects will take a relatively long time period to be relevant for fisheries. Overall

The csv data file “SAR_TBB.csv” contains data on habitat characteristics and fishing effort of the Dutch beam trawl fleet by grid cells of 1 minute longitude * 1 minute latitude in the North Sea used to study the changes in trawling impact on the benthic ecosystem due to the transition from conventional beam trawling to pulse trawling. Habitat variables include %sand, %gravel, %mud, bed shear stress (N.m-2) and level 3 EUNIS habitat type. Fishing effort, expressed as the annual swept area ratio (area swept by the gear in km2 / surface area of the grid cell (km2)), is given for the total Dutch beam trawl fleet and for a subset of vessels holding a pulse license (PLH) when fishing with the conventional beam trawl gear (PLH.T.year) or with the innovative pulse trawl (PLH.P.year)., The csv data file “SAR_TBB.csv” contains data on habitat characteristics and fishing effort of the Dutch beam trawl fleet by grid cells of 1 minute longitude * 1 minute latitude in the North Sea used to study the changes in trawling impact on the benthic ecosystem due to the transition from conventional beam trawling to pulse trawling. Habitat variables include %sand, %gravel, %mud, bed shear stress (N.m-2) and level 3 EUNIS habitat type. Fishing effort, expressed as the annual swept area ratio (area swept by the gear in km2 / surface area of the grid cell (km2)), is given for the total Dutch beam trawl fleet and for a subset of vessels holding a pulse license (PLH) when fishing with the conventional beam trawl gear (PLH.T.year) or with the innovative pulse trawl (PLH.P.year).

Information about the ecological connections between species is needed to make the shift from fisheries management strategies centred around single species to ecosystem-based fisheries management. Growth rates of fish strongly depend on the environment. Individual growth curves could therefore contain valuable information about the environmental conditions experienced by an individual throughout its life. In this study, we explored whether estimated growth curves contain information about the competition within and between species. We estimated growth curves for 10 species in 10 North Sea roundfish areas based on length-at-age data from the North Sea International Bottom Trawl Survey (NS-IBTS) fish survey by fitting a von Bertalanffy growth model with varying asymptotic length. From these model fits, we extracted a relative measure for the temporal variation in growth in body size of a stock, which can be used as an indicator of the experienced environmental conditions. We found signs of density-dependent growth in at least 6 out of the 10 species for some specific areas as well as all North Sea areas combined. In addition, we used cluster analysis to explore the relatedness in ecological growth conditions between species and areas. Ecologically related species tended to show more similar temporal variation in ecological growth conditions than ecologically more distant species. Likewise, areas that were geographically closer showed more similarity in ecological growth conditions compared to geographically more distant areas. This suggests that information on ecological conditions derived from growth curves provide a useful way to distinguish ecological groups or regions without the need for additional stomach sampling or ecological studies.

The pulse trawl is presented as an alternative for the traditional tickler chain beam trawl. The beam trawl has a direct lethal effect on the benthic community, which is much less for the pulse trawl. However, the pulse trawl, due to its electrical field has non-lethal effects on the benthic community. The existence of such non-lethal effects have been demonstrated for different organisms and most often involve a short period of inactivity. Such a period of inactivity may have consequences at the population level as it may limit feeding. Yet the population dynamical consequences, nor food web level consequences, have been studied in experimental or field settings. To study non-lethal and lethal effects of trawling on the benthic community a model was developed which is based on a trait-based characterization of the food web. This model describes the equilibrium dynamics of predators, filter feeders and deposit feeders. The model includes direct mortality as a function of fishing mortality and a non-lethal effect, which was incorporated as a decrease of the maximum food intake rate. This approach was based on experiments with electric pulse and benthic invertebrates. We conducted a comparative analysis of lethal and non-lethal impact of trawling on the equilibrium dynamics of the benthic food web. Only lethal effects represent a tickler chain beam trawl and a combination of lethal and non-lethal effect represents a pulse trawl. We first studied the effects of lethal and non-lethal impacts on the food web separately. We then studied the trade-off between lethal and non-lethal effects for a given total impact on the community. This approach shows how much non-lethal impact is required to compensate for a decrease in lethal effects of trawling. The study shows that lethal effects need to be replaced by non-lethal effects with similar strength in order to maintain the effect of fishing intensity on the food web. Such strong non-lethal effects are unlikely to occur in the

Ecosystem effects of bottom trawl fisheries are a major concern. We analysed whether the replacement of mechanical stimulation by electrical stimulation may reduce the adverse impacts on the benthic ecosystem in the beam trawl fishery for sole. Although the use of electricity is not allowed to catch fish in European Union waters, a number of beam trawlers got derogation and switched to pulse trawling to explore the potential to reduce impacts. We extended a recently developed assessment framework and showed that the switch to pulse trawling substantially reduced benthic impacts when exploiting the Total Allowable Catch of sole in the North Sea. We applied the framework to Dutch beam trawl logbook data from 2009 to 2017 and estimated that the trawling footprint decreased by 23%; the precautionary impact indicator of the benthic community decreased by 39%; the impact on median longevity decreased by 20%; the impact on benthic biomass decreased by 61%; the amount of sediment mobilised decreased by 39%. The decrease is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic impact of the beam trawl fishery targeting plaice Pleuronectes platessa in the central North Sea increased with the recovery of the plaice stock. This study illustrates the usefulness of a standardized methodological framework to assess the differences in time trends and trawling impact between gears.

Ecosystem effects of bottom trawl fisheries are of major concern. Although it is prohibited to catch fish using electricity in European Union waters, a number of beam trawlers obtained a derogation and switched to pulse trawling to explore the potential to reduce impacts. Here we analyse whether using electrical rather than mechanical stimulation results in an overall reduction in physical disturbance of the seafloor in the beam-trawl fishery for sole Solea solea. We extend and apply a recently developed assessment framework to the Dutch beam-trawl fleet and show that the switch to pulse trawling substantially reduced benthic impacts when exploiting the total allowable catch of sole in the North Sea. Using Vessel Monitoring by Satellite and logbook data from 2009 to 2017, we estimate that the trawling footprint decreased by 23%, the precautionary impact indicator of the benthic community decreased by 39%, the impact on median longevity of the benthic community decreased by 20%, the impact on benthic biomass decreased by 61%, and the amount of sediment mobilised decreased by 39%. The decrease in impact is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic physical disturbance of the beam-trawl fishery targeting plaice Pleuronectes platessa in the central North Sea increased with the recovery of the plaice stock. Our study illustrates the utility of a standardized methodological framework to assess the differences in time trends and physical disturbance between gears.

Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre‐exploitation levels and may have regained their prominent position as top predator in marine ecosystems. Also, the harbor seal population in the international Wadden Sea grew at an exponential rate following a ban on seal hunting in 1960s, and the current number ~38,000 is close to the historic population size. Here we estimate the impact of the harbor seal predation on the fish community in the Wadden Sea and nearby coastal waters. Fish remains in fecal samples and published estimates on the seal's daily energy requirement were used to estimate prey selection and the magnitude of seal consumption. Estimates on prey abundance were derived from demersal fish surveys, and fish growth was estimated using a Dynamic Energy Budget model. GPS tracking provided information on where seals most likely caught their prey. Harbor seals hauling‐out in the Dutch Wadden Sea fed predominantly on demersal fish, for example, flatfish species (flounder, sole, plaice, dab), but also on sandeel, cod, and whiting. Although harbor seals acquire the majority of prey further offshore in the adjacent North Sea, and only spend 14% of their diving time in the Wadden Sea, seal predation was still estimated to cause an average annual mortality of 43% of the remaining fish in the Wadden Sea and 60% in the nearby shallow coastal waters (<20 m). There were however large sources of uncertainty in the estimated impact of seals on fish, including the migration of fish between the North Sea and Wadden Sea, and catchability estimates of the fish survey sampling gear, particularly for sandeel and other pelagic fish species. Our estimate suggested a considerable top‐down pressure by harbor seals on demersal fish. However, predation by seals may also alleviate density‐dependent competition between the remaining fish, allowing for increased fish growth, an

Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre-exploitation levels, and may again act as a top-down regulatory force on marine ecosystems. Also the harbour seal population in the international Wadden Sea grew at an exponential rate following a ban on seal hunting in 1960's, and the current number ~38,000 is close to the historic population size. Here we estimate the impact of the harbour seal predation on the fish community in the Wadden Sea and nearby coastal waters. Fish remains in faecal samples and published estimates on the seal's daily energy requirement were used to estimate prey selection and the magnitude of seal consumption. Estimates on prey abundance were derived from demersal fish surveys, and fish growth was estimated using a Dynamic Energy Budget model. GPS tracking provided information on where seals most likely caught their prey. Harbour seals from the Dutch Wadden Sea fed predominantly on demersal fish, e.g. flatfish species (flounder, sole, plaice, dab), but also sandeel, cod and whiting. Total fish biomass in the Wadden Sea was insufficient to sustain the estimated prey consumption of the entire seal population year-round. This probably explains why seals also acquire prey further offshore in the adjacent North Sea, only spending 13% of their diving time in the Wadden Sea. Still, seal predation was estimated to cause an average annual mortality of 43% and 60% on fish in the Wadden Sea and adjacent coastal zone, respectively. There were however large sources of uncertainty in the estimate, including the migration of fish between the North Sea and Wadden Sea, and catchability estimates of the fish survey sampling gear, particularly for sandeel and other pelagic fish species. Our estimate suggested a considerable top-down control by harbour seals on demersal fish. However predation by seals may also alleviate density-dependent competition betw

An important consideration in assessing the impacts of fishing on seabed habitats is to understand the functional links (as trophic interactions) between populations of demersal fish species and potential benthic invertebrate prey (food) which live on or in the seabed. The type of sea-bed fauna has been shown to respond to both natural variation in habitat conditions and in response to different levels of fishing pressure. The extent to which different commercial fish species will depend on specific combinations of habitat type and fishing disturbance to feed will likely be species specific. It has been suggested that positive changes in growth rates of different demersal fish species are not only related to density-dependent processes, but may also be dependent on increased bottom-trawl disturbance and eutrophication (Millner and Whiting 1996, Rijnsdorp and van Leeuwen 1996, Shephard et al., 2010). However, different trawling and habitat specific responses in relation to fish feeding in different size classes of fish has not been investigated before. The aim1 of this study is therefore to examine such relationships using biological traits analysis (BTA) through a selected quantification of demersal fish stomach contents and habitat fauna using grab and epi-benthic trawl data previously analysed as part of BENTHIS deliverable D3.4. The present study addresses two important questions, namely; i. what type of sea-bed habitats serve as important feeding areas for different species of demersal fish, and ii. what, if any, differences do we observe in habitat preference and diet associated with different size classes of demersal fish, both within and between different fish species. Central to answering these two questions is the need to ensure that the sea-bed habitat characteristics are assessed and described at a scale appropriate to the operation of the fisheries and the assessment of demersal fish stocks. The study found strong associations between community trait com

A framework to assess the impact of mobile fishing gear on the seabed and benthic ecosystem is presented. The framework that can be used at regional and local scales provides indicators for both trawling pressure and ecological impact. It builds on high-resolution maps of trawling intensity and considers the physical effects of trawl gears on the seabed, on marine taxa, and on the functioning of the benthic ecosystem. Within the framework, a reductionist approach is applied that breaks down a fishing gear into its components, and a number of biological traits are chosen to determine either the vulnerability of the benthos to the impact of that gear component, or to provide a proxy for their ecological role. The approach considers gear elements, such as otter boards, twin trawl clump, and groundrope, and sweeps that herd the fish. The physical impact of these elements on the seabed, comprising scraping of the seabed, sediment mobilization, and penetration, is a function of the mass, size, and speed of the individual component. The impact of the elements on the benthic community is quantified using a biological-trait approach that considers the vulnerability of the benthic community to trawl impact (e.g. sediment position, morphology), the recovery rate (e.g. longevity, maturation age, reproductive characteristics, dispersal), and their ecological role. The framework is explored to compare the indicators for pressure and ecological impact of bottom trawling in three main seabed habitat types in the North Sea. Preliminary results show that the Sublittoral mud (EUNIS A5.3) is affected the most due to the combined effect of intensive fishing and large proportions of long-lived taxa.

A framework to assess the impact of mobile fishing gear on the seabed and benthic ecosystem is presented. The framework that can be used at regional and local scales provides indicators for both trawling pressure and ecological impact. It builds on high-resolution maps of trawling intensity and considers the physical effects of trawl gears on the seabed, on marine taxa, and on the functioning of the benthic ecosystem. Within the framework, a reductionist approach is applied that breaks down a fishing gear into its components, and a number of biological traits are chosen to determine either the vulnerability of the benthos to the impact of that gear component, or to provide a proxy for their ecological role. The approach considers gear elements, such as otter boards, twin trawl clump, and groundrope, and sweeps that herd the fish. The physical impact of these elements on the seabed, comprising scraping of the seabed, sediment mobilization, and penetration, is a function of the mass, size, and speed of the individual component. The impact of the elements on the benthic community is quantified using a biological-trait approach that considers the vulnerability of the benthic community to trawl impact (e.g. sediment position, morphology), the recovery rate (e.g. longevity, maturation age, reproductive characteristics, dispersal), and their ecological role. The framework is explored to compare the indicators for pressure and ecological impact of bottom trawling in three main seabed habitat types in the North Sea. Preliminary results show that the Sublittoral mud (EUNIS A5.3) is affected the most due to the combined effect of intensive fishing and large proportions of long-lived taxa