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BENTHIS Report Summary

Project ID: 312088
Funded under: FP7-KBBE
Country: Netherlands

Periodic Report Summary 3 - BENTHIS (Benthic ecosystem fisheries Impact Study)

Project Context and Objectives:
The sea bed provides a place to live for a wide diversity of plants and animals, but is also the source of an important economic activity: fishery. The impact of bottom trawl fisheries on marine life in and on the seabed is the subject of much debate, both in academia and among environmental NGOs, regulators, policymakers and fishermen. Fisheries may negatively affect benthic ecosystems, for instance by reducing biodiversity and sea bed integrity, but it has also been argued that bottom trawl fisheries enhances the food availability and growth of fish.

BENTHIS will provide the urgently needed knowledge to support an integrated approach to the management of human activities in the marine environment, in particular fishing (ecosystem approach to fisheries management). BENTHIS will study the vulnerability of different benthic ecosystems in European waters and analyse the physical impact of the current fishing practices on benthic organisms and geo-chemical processes.
In addition, in close collaboration with the fishing industry, BENTHIS will study and promote technological innovations to mitigate the impact. The project integrates ecological, socio-economic as well as fishing gear research, and is conducted by a consortium of research institutes, fishing companies and fishing gear manufacturers from all over Europe. Specific case studies will be conducted in the major European seas (Baltic Sea, North Sea, Bay of Biscay, Mediterranean Sea and Black Sea).

BENTHIS focuses on flatfish and shrimp fisheries with beam trawls, nephrops and roundfish fisheries with otter trawls, and shellfish fisheries with dredges. New management approaches will be developed in direct collaboration with the fishing industry and other stakeholders and their effects on the ecosystem and the socio-economic consequences
will be tested. BENTHIS will inform managers about the benthic habitats that are impacted most and about the fishing gears that have the biggest impact and provide information on options to mitigate these impacts.

BENTHIS will organize regional stakeholder events with representatives of the fishing industry, NGO’s, policy and research to advice on priority research questions, provide feed-back on the results and enhance the dissemination of the results.
The main objectives are to
• Provide the knowledge base that allows an assessment of the status of different types of marine benthic ecosystems in European waters on a regional basis and support indicators of Good Environmental Status (GES), in particular on Seafloor Integrity;
• Develop the tools required to assess the effects of bottom trawling on structure and functioning of these benthic ecosystems;
• Study and test, in close collaboration with the fishing industry, innovative technologies that reduce the impact of demersal fisheries on benthic ecosystem on a regional basis, encompassing the Baltic Sea, North Sea, Western Waters, Mediterranean and Black Sea;
• Develop in consultation with the fishing industry and other stakeholders on a regional scale, sustainable management plans that reduce the impact of fishing and quantify its ecological and socio-economic consequences.

Project Results:
The work plan comprises of generic work packages where tools are developed to assess bottom trawl impact on benthic ecosystems, and a Case Study work package where the tools are applied to specific fisheries.
The footprint of 14 European bottom trawl metiers, matching the Data Collection Framework classification, was estimated. The footprint is based on the dimensions of the individual gear components, such as trawl doors, sweeps and ground gear, obtained from an industry-based vessel and gear survey covering 13 different countries. Relationships between gear width and vessel size (e.g. trawl door spread and vessel kW) for each metier were used to assign quantitative information about bottom contact to each logbook trip. VMS and logbook data were used to quantify the spatial distribution of bottom trawl intensities in the Baltic Sea, North Sea, western waters and eastern Mediterranean Sea at a spatial resolution of 1 * 1 minute longitude and latitude. The results highlight areas and sea bed habitats with highest trawling pressure, but also show that in most regions a substantial part of the sea bed was left untrawled. Trawling intensities were analysed for the dominant EUNIS level 3 habitat types in all regions.

To reduce the enormous species richness, benthic invertebrates were grouped into a smaller number of classes that share certain characteristics (traits) and that define their role in the ecosystem and relate to their sensitivity for trawling impacts. A biological traits data base was compiled consisting of over 1000 benthic invertebrate species. Each species was classified according to 10 principal trait categories (maximum size, morphology, longevity, larval development, living habitat, sediment position, egg development, feeding, mobility, bioturbation), and each trait supports a number of modalities, resulting in a total of 48 trait variables. The definition and relationship between benthic biological traits, biological processes, functions and provision of benthic ecosystem goods and services has been agreed and defined. The data corresponds to 16 EUNIS habitat types. Experimental investigations were undertaken to evaluate experimentally the ground forces and the amount of disturbed sediment of towed gears. Field studies were carried out to measure sediment mobilisation in relation to hydrodynamic drag. Numerical studies were carried out on the influence of the dimensions, weight, cross sectional geometry and soil material properties have on the penetration and drag of truncated rigid cylinders towed over fully saturated muddy soils and sandy soils.

A framework was developed to estimate the amount of discards sinking to the sea bed. The framework integrates data on the spatio-temporal variation in seabird distribution, seabird attraction to fishing vessels and discard distribution. The framework was applied to the Bay of Biscay.

A systematic review of the literature of trawling impact on benthic invertebrates showed that (i) the initial effect of bottom fishing on the abundance varies among species with different biological traits; (ii) the magnitude varies among different habitat types and fishing gears, and (iii) the temporal trajectory for recovery from bottom fishing activity varies among species with different biological traits. Bottom fishing resulted in significant negative impacts on total benthic community abundance; reductions were significantly higher following dredging (33% loss) compared to otter and beam trawling (5% loss), and they were most severe for benthic communities in biogenic habitats and coarse and mixed sediment relative to sandy and muddy sediments.

Different studies examined the effect of bottom trawling on food intake of benthivorous fish. The work shows that there is no strong evidence to suggest that bottom trawling has a substantial positive or negative effect on commercial fish populations by affecting their food supply.

A risk assessment framework is developed to compare the pressure bottom trawling and the impact on the benthic community composition and benthic ecosystem functioning at regional or local scales. The method has been applied on the three dominant habitat types of the North Sea suggesting that trawling impact is highest in muddy sediments (EUNIS A5.3).

A framework for the analysis of the economic performances of alternative fishing gears was developed. A model of the dynamics of effort allocation (short-term) was made available in R and has been used to study discarding decisions relevant to the implementation of the landing obligation, and the transition from a tickler chain beam trawl fleet to a fleet using electrical pulse trawl targeting North Sea sole.

A review of possible management measures to mitigate trawling impact on the benthic ecosystem was made. Two decision-support tools were developed: sea floor impact reduction tool aimed to reduce the impact of fishing on the sea floor through a change in the behaviour of fishers; a multi-criteria analysis for the evaluation of management strategies taking stakeholder preferences into account.

Case studies were carried out in the Baltic Sea, North Sea, Western Waters, Mediterranean Sea and Black Sea to study current impact of bottom trawling and study possibilities for mitigation in collaboration with the fishing industry and gear manufacturers. The case studies focussed on technological innovations (semi-pelagic doors, electrical stimulation), gear substitutions (passive gears) and smart fishing (avoid vulnerable habitats) to reduce the benthic impact. Fisheries studies include: Nephrops and roundfish otter trawling; beam trawling for flatfish and brown shrimp; dredging for scallops and blue mussels. Field trials with innovative gears were continued in collaboration with the fishing industry and gear manufacturers. In the Mediterranean Sea, wind tunnel experiments were conducted with semi-pelagic doors.

Successful regional stakeholder events were held during which the objectives and progress made was discussed. Around 100 stakeholders representing the fisheries sector (48%, fisheries related industry (7%), government (11%), NGO (4%) and scientist (30%) participated in one of the 5 events. Areas of harmony, conflict and opportunities for technical and sustainable management initiatives were identified and mapped.

BENTHIS results have been disseminated in the scientific literature (21 papers published and four papers submitted to peer reviewed journals). In total 42 oral or poster presentations were given at scientific meetings. Further BENTHIS results have been used in national projects, and have been presented at ICES Working groups that provide input to the development of MSFD-indicators (Working Group on the Ecosystem effects of fishing (WGECO: 2 participants), Working Group on Spatial Fisheries Data (WGSFD: 3 participants). In response to a request from EC DG ENV to ICES on “guidance on how pressure maps of fishing intensity contribute to an assessment of the state of seabed habitats“, a workshop WKFBI was organised through which the BENTHIS work fed directly to the advice produced by ICES. WKFBI was chaired by the BENTHIS coordinator and attended by 5 BENTHIS researchers.. The BENTHIS contribution comprised of two quantitative methods developed (longevity approach, population dynamic approach). In the advisory process, these methods were favourably reviewed and will be used in the next step to further develop indicators for trawling impact and sea floor integrity by ICES in 2017.

Potential Impact:
BENTHIS will make an important contribution to advancing the knowledge base on the ecosystem effects of fishing, in particular on the effects of bottom gear on sea bed habitats and benthic ecosystems. The BENTHIS approach is to develop quantitative tools that are generic and therefore applicable in a broad range of benthic habitats and ecosystems and to a broad range of fishing gear. The methodology will allow a quantitative assessment of the impact of fishing (trawl) gear on benthic ecosystems and the economic consequences that will be applied in regional case studies. Indicators of the impact of fishing on the benthic ecosystem will be developed that are consistent with the Marine Strategy Framework Directive. BENTHIS offers perfect opportunities for collaboration between partners that will promote research of excellent scientific quality with high impact for science and society.

The collaboration with the fishing industry in the regional case studies, and the involvement of the fisheries and other stakeholders in the (regional) stakeholder events, will warrant that BENTHIS will address the questions that are relevant for the transition process in the various case study areas to reduce the benthic impacts through technological innovations and innovative management measures. BENTHIS is well attached to a variety of national research programmes. Together with the regular interactions with stakeholders, this will enhance the dissemination of the knowledge produced.

The collation of the VMS and logbook data will provide the first European wide map of trawling intensity of European seas distinguishing between the impact restricted to the sea bed surface and the impact of gear components that penetrate into the sediment. The analysis of the trawling intensity in relation to the benthic habitats and benthic ecosystems will allow a quantification of the impact on the ecosystem structure and functioning revealing areas - fishing gear combinations that are most impacted.

The effect on the fisheries impact of innovations in fishing technology and management measures, agreed upon in the stakeholder consultation process, will be quantified. The results will be discussed with the stakeholders and communicated to the fisheries managers and are expected to have an immediate bearing on the development of the ecosystem approach to fisheries management. Successful technological innovations will strengthen the economy of the fishing sector.

Results of BENTHIS will be published in scientific publications and presented at scientific meetings in Europe and beyond. Input will be given to the related working groups of ICES and to the globally operating Trawling Best Practice project.

List of Websites:

Related information


Adrianus Dirk Rijnsdorp, (Senior scientist IMARES)
Tel.: +31 317487191
Record Number: 197939 / Last updated on: 2017-05-16
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