A sea under pressure: Bottom trawling impacts in the Baltic

WWF Baltic Bottom Trawling Storymap

A sea under pressure

This story map is meant as a platform to raise awareness around the potential impacts of bottom trawling in the Baltic Sea and to ensure we safeguard its health. - WWF Baltic Ecoregion Programme

The Baltic: A unique environment

The Baltic Sea is a semi-enclosed sea that connects people of nine nations: Denmark, Estonia, Latvia, Finland, Germany, Lithuania, Poland, Russia and Sweden. Around 15 million people live along the Baltic’s coastlines, while a further 75 million people in the region live inland.

The Baltic Sea is the youngest sea on earth. Emerging from the retreating glaciers of the last Ice Age around 10,000 years ago, its shallow, brackish waters are made up of a delicate mixture of saltwater from the Atlantic, and freshwater from connecting rivers and streams.

For those of us who live in the region, the Baltic Sea has been sustaining and shaping our cultures for centuries. It is woven into the backdrop of our shared history, forming an integral part of the stories from our everyday lives and of the traditions passed from generation to generation.

A diverse range of marine and freshwater species make their home in the Baltic Sea, each adapted to thrive in its unique marine environment. From microscopic plankton to communities of fragile seafloor animals, dense seagrass beds, familiar fish like cod, herring, salmon and pike to seabirds and large marine mammals, such as the grey seal. The animals, plants and habitats of the Baltic Sea are interconnected and interdependent in many ways. Click on the arrow on the right of the screen to explore some of the flora and fauna that form part of this ecosystem. 

Seagrass beds

Seagrass (sometimes called eelgrass) is a flowering plant that can form dense beds on sandy and muddy seafloors in sheltered, shallow waters where enough sunlight penetrates for them to grow. Seagrass beds serve a variety of vital functions in the ecosystem. Their root systems bind and stabilise seabed sediments, protecting beaches from erosion, and the beds provide food and shelter to a wide array of animals, including the juvenile forms of many fish species, and are carbon sinks.

Seagrass beds also provide a home to small invertebrates, such as these tiny grazing Rissoa snails, ...

... and these young common starfish.

Seagrass can grow very fast, which means it is incredibly efficient at binding carbon: Seagrass beds are “blue forests” that, like forests on land, can help us address the challenge of climate change. Blue forests can also be formed by seaweed. In this image of a seagrass bed, you can also see some tufts of seaweed with little air bladders in its fronds that lift them up above the seagrass bed. This is called bladder wrack.

Bladder wrack (and other seaweeds) 

Bladder wrack is a brown seaweed that is a familiar sight to beachgoers, as it often washes up on the shore. Bladder wrack can have different growth forms, including the dwarf form shown in this image.

Seaweeds are primary producers of biomass, trapping the sun’s energy through photosynthesis – a function they share with microscopic algae (known as phytoplankton). Together, these primary producers are the foundation of the marine food web. 

Kelp on a whelk 

Seaweeds tend to prefer to grow on a stable seafloor that they can attach to securely – this includes areas of rock or sheltered sediment. When there is no suitable hard seafloor, however, seaweed can also attach itself to other hard substrates such as the kelp that has found a home on the shell of this whelk, travelling across the sandy seafloor of the Hirsholmene Marine Reserve in the Kattegat. 

Adult brown crabs are reddish-brown colour, while the young are purple brown. Occasionally their shells have white patches and have a front edge with rounded lobes that resemble a pie crust. Reproduction occurs in winter; the male stands over the female and forms a cage with his legs protecting her while she moults.

Eastern Baltic cod and Western Baltic cod

With its barbed lip, the cod is perhaps one of the most familiar and iconic marine fish species in northern Europe. It is a popular food and one of the most important commercial fish species of the Baltic. It spends much of its life on or near the seafloor, there are two main populations (eastern and western) in the Baltic. Although it can live throughout the whole sea, it can’t reproduce in the far northern areas where the salinity of the water is very low. Its most important spawning areas are in the deeper areas of the southern Baltic (off Germany, Poland and Denmark) and the coastal waters of the western Baltic and in the Danish Straits.

Baltic flounder

A master of disguise, this migratory fish spends much of its summers hiding on muddy and sandy seafloors in shallow, brackish waters, often entering freshwater in river estuaries. During winter, adults retreat to deeper, warmer waters, where they spawn in spring, their growing larvae moving back to shallow waters of the coast, where they are safer from predators. 

Arctic tern

The arctic tern has the longest migration of all birds, spending the southern summer season in the Antarctic, and flying to the Arctic and northern temperate region where it breeds during the northern summer. The Baltic Sea forms part of the breeding range of this remarkable seabird. 

Common guillemot

The common guillemot is another remarkable bird, having become adapted to spending most of its life at sea, returning to coastal cliffs only to nest and breed. It occurs throughout the northern Pacific and Atlantic, including in the Baltic. The largest breeding colony in the Baltic Sea is on the island of Stora Karlsö nearby to the island of Gotland.

Harbour porpoise 

The harbour porpoise is a small toothed whale that is widely distributed across the temperate seas of the northern hemisphere. There are two distinct populations of harbour porpoise in the Baltic Sea, one in the south-eastern part, and one in the south-western part. Both populations have suffered significant declines in recent years, and efforts are underway to better protect these marine mammals.  

The Baltic is under a lot of pressure 

A hotspot of human activities

The Baltic Sea is under extreme pressures from human activities. It is suffering among other things from,  eutrophication , contamination of  hazardous substances , dredging,  invasive species,   seabed loss and disturbance , and long-term unsustainable  overfishing . As a result of all these human pressures and poor management, the natural resources we depend upon in the Baltic are quickly becoming depleted beyond safe biological limits—jeopardizing future ecosystem goods and services.

Click on the buttons below to explore data layers showing the distribution of some of the human activities in the Baltic Sea (data sourced from HELCOM). Click on a button twice to bring up all four layers together.

To ensure that the Baltic Sea remains a healthy and abundant resource, both now and for future generations, it is critical that we take collective action to protect it.

Fishing pressure as a threat 

Fishing is one of the most widespread and significant direct impacts that humans have inflicted on marine ecosystems, and the Baltic is no exception. One sign of the crisis unravelling is the vulnerable status of both the wild salmon and Baltic cod populations. Damaging practices, quotas set beyond scientific guidelines, high levels of bycatch, ongoing discarding, and illegal, unregulated and unreported fishing are all leading to extensive ecosystem degradation. Given the current state of chronic overfishing, along with a multitude of environmental pressures and anthropogenic activities, stock recovery is unlikely unless we begin to listen to science and drastic action is taken. 

This map shows the distribution of fishing effort (represented as the number of fishing hours) in the Baltic Sea for all types of fishing combined. The sea is divided into regular grid cells, and each cell is shaded to show the number of fishing hours within that cell for the year 2013. You can zoom in or out on the map using the buttons in the bottom right, and clicking on an individual grid cell will bring up a pop-up box showing the number of fishing hours for that cell.

The information is based on VMS/Log book data processed by the ICES Working Group on Spatial Fisheries Data, supplied via HELCOM, and 2013 is the most recent year for which this processed and combined dataset for all types of fishing gear is available. No data are available for areas falling under Russian jurisdiction. 

Bottom trawling as a threat

There are different types of fishing gear in use in the Baltic. Open sea fisheries, which account for the largest catches by weight, use midwater-trawling techniques to catch sprat and herring. However, the largest cod and flatfish fisheries use bottom trawling techniques, in which nets are dragged across the seafloor. Out of all the fishing practices in the Baltic, bottom trawling is one of the most damaging. Unfortunately, it is a common practice in the region, particularly the southern Baltic.

The map shows the average intensity of bottom trawling in the Baltic Sea, derived from Vessel Monitoring System data for 2016 (the most recent year for which this derived data was available). Darker colours indicate higher bottom trawling intensity, concentrated in the south-western part of the Baltic. 

This map shows the distribution of bottom trawling (represented as the number of fishing hours) in the Baltic Sea for the year 2016, using the same grid cells as the previous map. You can zoom in or out on the map using the buttons in the bottom right, and clicking on an individual grid cell will bring up a pop-up box showing the number of bottom trawling hours for that cell.

The information is based on VMS/Log book data processed by the ICES Working Group on Spatial Fisheries Data, supplied via HELCOM, and 2016 is the most recent year for which this processed and combined dataset for bottom trawling is available. No data are available for areas falling under Russian jurisdiction.


What is bottom trawling?

Bottom trawling is a term that broadly describes mobile fishing gear and techniques that come into contact with the seabed and are used to catch fish and other bottom-dwelling species living on, near or in the seabed. During bottom trawling, fishing gear is manually or mechanically dragged behind a boat with constant or occasional contact with the seabed. The weighted nets are typically made from small strong mesh equipped with specific types of ground gear that can withstand bottom impact.

With technology improvements in recent decades, including sonar technology, modern trawlers are now capable of fishing areas that were once avoided for fear of damaging nets.

As the net drags across and digs into the seafloor, it stirs up sediment, destroys fragile creatures, and catches almost everything in its path. These immediate impacts are illustrated in this video.  

How Seafood is Caught: Bottom Trawling

There are two main types of trawling gear commonly used in the south-western Baltic today, the otter board trawl and demersal seine. Baltic cod and flatfish were the main target species up until recently. In 2019, a ban on fishing the collapsed Eastern Baltic cod stocks led to a switch in target species to flatfish, though cod is still caught as a bycatch (accidental/non-intended catch).

Otter Board Trawl

The otter board trawl has a cone-shaped net that ends in one or two bags (“codends”) that hold the catch. The front of the net is kept open horizontally by two otter boards, which are also sometimes called doors. The vertical opening has a headline with floats and heavier ground gear that penetrates the top of soft sediments. Rubber bobbins or disks prevent penetration into the ground on rough bottoms. Tickler chains located in front of the opening are often employed to disturb flatfish from the seafloor and make them swim into the net.

Demersal Seine

Demersal seine gear are applied by laying long lengths of weighted rope and a seine net on the seabed in a circular or triangular pattern. When the weighted ropes and seine net are hauled towards the boat, they drag along the seafloor, impacting habitats and organisms in their path.


The impacts

Bottom trawling is non-selective and highly damaging

The impacts of bottom trawling on marine ecosystems are well-known from studies around the world. Click on the video on the right to see a trawl net dragging across the seafloor. Bottom trawling wreaks havoc on seafloor habitats and the species that depend on them. The case studies at the end of this story map demonstrate the profound changes it causes (as well as the recovery that is possible when it is stopped). Taking a precautionary approach, strict regulation should also be applied to bottom trawling in the Baltic Sea to safeguard its unique ecosystem.

Removal of rock structures, grasses, and algae

Bottom trawling destroys a wide range of fragile plants and animals on the seabed, including those that form habitats with important ecosystem functions. This includes seagrass beds and reef structures formed by mussels and seaweeds, as well as other fragile organisms on the seafloor. Heavier trawls can even damage or destroy rocks and boulders on the seafloor, degrading the hard substrate that plants and animals live on. 

Changing the balance between species

The physical impacts on the seafloor tend to homogenize the seabed by removing organisms that create three-dimensional habitat structure. This removes the living space for many types of organisms, shifting the balance between species towards a smaller number of organisms resistant to physical disturbance.

Damage to seafloor habitats, species distribution and abundance

This shifting balance between species creates depleted ecosystems. The heavier the trawl net and the softer the sediment, the more easily gear can penetrate the seabed, stirring up clouds of sediment, leaving behind trawl marks on the seabed, and negatively impacting even those organisms that live beneath the surface. In one study, a single fishing gear pass diminished the abundance of invertebrate animals on and in the seabed by 26%, and reduced species richness by 19% ( Sciberras et al. 2018 ). Fragile, complex structures and habitats with soft bottoms and sessile, long-lived animals like mussels and clams are the most vulnerable and take the longest to recover. Records of seafloor species in the Kattegat show that, compared to the 1880s, about 30% now live in areas of shallower depths that aren’t fished ( Josefson et al. 2018 ).

Serial depletion of fish stocks

As fish are removed and important seafloor fish habitats destroyed, fish stocks can’t recover. Any attempts at maintaining catch size over time require increased fishing effort being expended, which often includes moving into new areas which soon become depleted, too.

Bottom trawling alters ecosystem balance and reduces species complexity.

This diagram is a highly simplified representation of the food web of the Baltic Sea. Phytoplankton (microscopic plants) grow by using energy from the sun, creating food for zooplankton (microscopic animals), and for larger organisms that live in the open sea and on the seafloor. Seafloor fish (including those targeted by bottom trawls) both eat and are eaten by a range of larger organisms. In coastal areas, plants attached to the seafloor produce food for coastal fish (which also eat phytoplankton and zooplankton), and provide shelter for juvenile forms of open water and seafloor fish. Mussels attached to the seafloor filter organic matter from the seawater, providing a food source for seabirds, along with fish.

The removal of target fish species causes knock-on effects that reverberate around this ecosystem. Bottom trawling has, for example, removed a lot of cod from the Baltic Sea, so the biomass of Baltic cod has been in decline since the 80s. Meanwhile, populations of sprat (the cod’s main prey) have increased four-fold. Sprat prey on cod eggs, and they also compete with cod larvae for their main food (zooplankton), thereby impacting on cod reproduction and causing zooplankton populations to decline. Less zooplankton has, along with other factors, allowed the biomass of their food (phytoplankton) to double, thereby exacerbating one of the main environmental problems in the Baltic Sea, namely the occurrence of harmful algal blooms that can deplete entire zones of oxygen.

Bottom trawling can cause significant imbalances in the food web and can contribute to a collapse in fish stocks such as cod.

Biogeochemical cycles (e.g. the carbon cycle, the nitrogen cycle) are circular flows of vital elements between living organisms and the physical environment. Bottom trawling is disrupting some of these vital cycles in the Baltic Sea, by digging into soft sediments and stirring them up (as seen in this video). As a result, water transparency declines, less light penetrates the water and seagrasses can not grow as deep leading to less fish habitat, and harmful nutrients, substances and organic contaminants are released into the water column.

This includes carbon. In the absence of physical disturbance, organic carbon settles and becomes locked into seabed sediments over time. This slow process, called carbon sequestration, is critical for the regulation of the climate, but it is disrupted and impeded by bottom trawling.

The plight of cod

The story of the cod – an iconic species of the Baltic Sea - illustrates the damaging impacts of bottom trawling and overfishing. 

Baltic cod can have a natural lifespan of 25 years and grow up to one and a half meters in length. Use the slider on the image below to see the difference between the 31 kilogram cod caught by a Baltic fisherman in 1994 in the deep waters surrounding Åland, outside of Grisslehamn, and a typical cod you might catch in the Baltic today.   

Due to many factors, including overfishing, most of the cod landed in the Baltic Sea today are only approximately 30 centimetres in length. Fishing targets the biggest individuals first, removing them from the population until only smaller individuals remain. There is even evidence that this has created evolutionary pressure for cod to stay small as adults.

Where is bottom trawling happening in the Baltic? 

Bottom trawling is particularly prevalent in the southern part of the Baltic Sea. The map shows the distribution and intensity of bottom trawling from 2009 up to the beginning of 2017. For each of these years, the map shows the distribution of bottom trawling (represented as the number of fishing hours), using the same grid cells as the previous fishing effort maps.

You can move the slider at the bottom to change between the years, and you can also zoom in or out on the map using the buttons in the top left. Clicking on an individual grid cell will bring up a pop-up box showing the number of bottom trawling hours for that cell.

The information is based on VMS/Log book data processed by the ICES Working Group on Spatial Fisheries Data, supplied via HELCOM. No data are available for areas falling under Russian jurisdiction.

Even Marine Protected Areas are trawled

The Baltic Sea is home to important and valuable wildlife. This has been recognized by national and international authorities, who have designated many places in and around the Baltic Sea as marine protected areas (MPAs), intended to protect nature and give it the space it needs to recover and flourish. The map shows HELCOM MPAs (designated under the Helsinki Convention). A lot of these are also protected under EU legislation (as part of the Natura 2000 network). 

In MPAs, nature should be protected from the worst of direct human impacts. When MPAs are well managed and designed as representative networks, they protect biodiversity and build ecosystem resilience, allowing habitats to recover from past damage. Healthy populations within MPAs also help replenish other areas of sea, including for commercial fish stocks (an effect known as “spillover”).

However, despite recent efforts to protect some habitat types from trawling, MPAs in the Baltic still aren’t properly protected from damaging impacts: Bottom trawling extends into the boundaries of virtually every MPA in the south-western part of the Baltic. The map illustrates this by overlaying the MPA boundaries with the gridded trawling intensity scores from 2016. 

The red areas on this map show where bottom trawling happens within MPA boundaries (based on the bottom trawling data from 2016). To safeguard the integrity of MPAs, this must change.

What we recommend to protect marine protected areas:

Bottom trawling also extends into cod spawning areas, as shown on this map.

While there are bottom trawling closures during spawning season, juvenile cod need the shelter of healthy and intact seafloor habitats, so allowing bottom trawling to occur in these areas at any time of the year impedes the replenishment of the main species targeted by that same fishery by destroying their habitat. A lot of important cod spawning and nursery areas are located within 12 nautical miles of the coast, along with sensitive habitats such as seagrass beds that contribute to climate change mitigation and provide opportunities for localised coastal fisheries with low impacts on the seafloor.

What we recommend to protect and restore coastal habitats:

Bottom trawling does not impact on all types of seafloor habitat to the same degree. To illustrate this, consider the areas that fall within the three highest intensity score categories (based on 2016 data), outlined here with a black line. 

This map shows the seafloor habitat types within these most intensively trawled areas. There are five main types of seabed habitat in the Baltic Sea: bedrock, hard bottom, hard clay, mud and sand. The map illustrates that most of the trawled area has sediment (mud and clay) seafloor, while bedrock and hard bottom areas are trawled less. As outlined earlier, when left undisturbed, sediment habitats are home to species that form three-dimensional structures that provide living space to other organisms, and they are also effective at storing carbon. These functions are being severely disrupted by bottom trawling.

What we recommend to protect seabeds:


Opportunity for change

Translating policy and legislation into action 

Policy and legislation to support the protection of the marine environment already exists at the international and national level, providing a foundation for safeguarding the Baltic ecosystem. 

 

The Helsinki Convention, established to address environmental degradation of the Baltic Sea and signed by all nine Baltic coastal countries, has been in place since 1974 (along with its governing body, the Helsinki Commission or HELCOM). The Helsinki Convention provides an international framework for addressing land-based pollution that enters the Baltic Sea, as well as for managing maritime activities. 

Eight of the Baltic countries are EU members, subject to EU legislation. The Habitats and Birds Directives oblige all EU members to protect a range of species and habitats on land and at sea, within a network of protected areas known as the Natura 2000 network.

The marine Natura 2000 network is an important contribution towards the EU Marine Strategy Framework Directive, which obliges all EU members to create an ecologically representative network of MPAs, along with other measures to ensure that all EU marine waters achieve Good Environmental Status. 

These international laws – shown here in green – all have the central aim of safeguarding environmental integrity. There are other important EU laws to consider, which aim to manage maritime activities efficiently. 

One of these is the EU Common Fisheries Policy (CFP). In shared EU waters, all fisheries management measures – including restrictions on fishing activity that are necessary to safeguard the environmental integrity of MPAs – must be implemented through the CFP. In principle, the CFP allows bottom trawling in all areas, unless they have been specifically closed (in the Baltic, some spawning areas are seasonally closed to bottom trawling to safeguard the replenishment of fish stocks). Measures to restrict fishing must always be implemented under the CFP, even if they are put in place to protect MPAs established to comply with the MSFD or the Habitats and Birds Directives.

Over the last decade, the EU Marine Spatial Planning Directive and Integrated Maritime Policy have been developed to facilitate cross-sectoral integration in marine management. The EU Marine Spatial Planning Directive provides an overarching framework for managing space at sea, ensuring space for nature conservation and for maritime activities, while the main purpose of the EU Integrated Maritime Policy is to ensure that maritime activities are managed efficiently.

The countries around the Baltic Sea need to translate existing conservation-focused legislation into effective management action, including by ensuring that fisheries and other maritime activities are managed in a way that safeguards the integrity of the marine ecosystem. To date, however, they have failed to properly implement and enforce existing environmental laws and policies, or to fund proper monitoring of human activities and their environmental impacts. As a result, none of the existing policy and legislation has stopped the pollution, degradation and overfishing of the Baltic Sea.

Within the existing legal and policy landscape, there are a number of specific actions should urgently be taken, in addition to the three recommendations in the previous section. These are:

To ensure they are effective, these specific measures should be embedded in a wider fabric of good ocean management and based on reliable science. In an enclosed sea like the Baltic, surrounded by nine different jurisdictions, collaboration is vital for safeguarding ecosystem health. This should be underpinned by well-funded and transparent governance processes and the effective sharing of scientific data. To this end, three further recommendations are:

Finally, the existing legal framework should be leveraged to develop a holistic, ecosystem-based approach to managing the Baltic ecosystem and the human activities that impact on it. A vital aspect of this is to safeguard space for nature to recover and thrive through the establishment of well-managed, representative and ecologically connected marine protected area (MPA) networks. At its core the Baltic MPA network should include a network of strict-no take zones, which should cover a combined total of no less than 10% of the Baltic Sea area. The final recommendation, therefore, is the following:

We can and should be doing more to protect this invaluable ecosystem for both nature and people 

Leaders and decision-makers in the region are urged to unify efforts to protect the Baltic. Given the region’s geopolitical diversity, finding common ground on complex issues such as environmental protection, sustainable use and management is an ongoing challenge. One that we urgently need to overcome. Time is running out.

Given a chance the Baltic seabed can recover — if we take action now!


Four cases that show recovery is possible 

The Côte Bleue Marine Park, France – an example of collaborative stakeholder governance using an MPA and no-take zones

Established in 1983 next to Marseille, France, and included in a Natura 2000 site, the Côte Bleue Marine Park provides an interesting case study of how MPAs can deliver on ocean governance. The park aims to protect Natura 2000 habitats and species, including Posidonia meadows (a type of eelgrass native to the Mediterranean). It contains two no-take zones (shown in the map in green) where all fishing is forbidden, along with diving, dredging and anchoring. In the rest of the park, all activities are authorised and subject to the general regulations at sea. The reserves in the Côte Bleue Marine Park were jointly constructed by MPA authority managers and fishers.

The park has succeeded because it has enforced the two no-take zones and because fishers have been active partners involved in the management and monitoring. Other areas of success are the committed long-term governance from local authorities and elected officials, the experimentation and innovation in management (e.g. artificial reefs), the educational outreach in the form of classes, and the local support of residents and users. Several studies have highlighted tangible results, such as the fact that fishers now have a more positive perception of their relationship with MPA managers. Other stakeholders have also been actively engaged through the Natura 2000 governance.

Isle of Arran, Scotland – an example of a well-managed MPA and no-take zone

The Isle of Arran lies in the Firth of Clyde off the west coast of Scotland, where intense bottom trawling and dredging (mainly for scallops) caused significant damage to the seabed in the 1980s. Following 13 years of campaigning by the local community, a no take zone of 2.67 square kilometres was finally established to protect the seabed in Lamlash Bay, banning fishing in the area. This no-take zone is shown in green in the map above. It is embedded in a larger MPA (shown in blue), created to protect eelgrass beds, mussel beds, maerl beds (formed by a type of seaweed that creates a hard skeleton) and sponge communities. Since the protection, biodiversity has increased substantially, along with size, age and density of commercially important species. Seagrass returned, mussel beds quadrupled since 2013, and the cod recovered along with the lobster population—which produces six times more eggs than outside the no-take zone. Research has also revealed differences in nursery habitats and other behaviors in the three main commercial fish species (cod, haddock and whiting) inside the MPA with cod responding positively to higher benthic biodiversity and landscape heterogeneity.

The protected area continues to have strong local advocates, who have formed a local community organisation (the Community of Arran Seabed Trust or COAST) that collaborates with scientists to monitor the site, and networks with other similar local initiatives developing in Scotland. The following video introduces the site and some of its local champions:

Öresund, Denmark – an example of a successful spatial closure

The strait of Öresund in Denmark provides an example of how the knock on effect of restricting bottom trawling can benefit cod and overall marine ecosystem. Varying between 5 and 45 km wide, the strait is the primary route for ships traveling between the North Sea and Baltic. Because of the danger to shipping, mobile fishing gears like bottom trawls have been banned from the Öresund (shown in green on the map) since 1932. Within the area called Kilen (shown in blue on the map), bottom trawling is banned from 1 February to 31 March, during the most intensive cod spawning period. However, hooks, nets and traps have been used throughout this time outside shipping lanes. Although not fully protected from fishing, and despite the small size of this de facto protected area, cod have clearly benefited greatly from the exclusion of bottom trawling. Research on catches shows that cod are 15–40 times more abundant in the Öresund than in the Kattegat and exhibit better size-structure than cod stocks that are predominantly trawl-caught.

Today primarily caught with gillnets, the Öresund cod exhibit better size structure than the cod stocks that are predominantly trawl-caught and has become an economically important recreational area for anglers and tourism. The ecosystem services provided in the Danish/Swedish sound are many due to the eelgrass, kelp and mussel beds communities providing feeding grounds for birds and migratory routes for many fish species.

The Gulf of Castellamare, Italy – an example of a productive trawl ban

In 1990, a trawling ban was implemented in the Mediterranean Sea’s Gulf of Castellammare over an area of approximately 200 km2 - 55% of the entire gulf. The ban allows fishers to use all non-towed bottom and pelagic gears, and permits artisanal and recreational fishing, diving and other touristic uses of the environment. Since the ban, there has been significant increase in fish biomass within the gulf—four years into the ban the total fish biomass increased eightfold. Fifteen years after the ban, a survey showed that the fish biomass of all size classes was higher in the protected Gulf of Castellammare compared to unprotected areas. Moreover, the catch per unit of effort was higher, meaning it takes less effort to catch the same amount of fish in the trawl-free area.


Recommendations

Action for a healthier Baltic is more urgent than ever 

In the context of our planet’s converging biodiversity and climate crises, collective action to reduce harmful bottom trawling activities in the Baltic is more urgent than ever. A healthy seafloor and good environmental status supports a greater fish biomass, and a more resilient ecosystem as a whole, which in turn supports human’s well-being and livelihood.

Considering the fragile system of the Baltic Sea environment we need to tread very carefully. Foremost, there is still a lack of complete understanding the multiple effects of bottom trawling and therefore the ‘business-as-usual' must adhere to apply the precautionary approach. 

It is the governments’ legal responsibility to ensure that human activities are not harming GES. In this context, WWF calls on Baltic Ministers to work across their authorities and intensify their efforts of achieving sustainable fisheries and Good Environmental Status in the Baltic Sea.

A regionally agreed method for assessing seafloor integrity must be adopted by the Baltic Sea countries to assess the cumulative impacts and recovery rates of various seabed habitats. It’s also important to establish a baseline that will enable us to monitor, research and evaluate how our actions—legislation, implementation, management, and enforcement—are working.

We propose the following actions in order to restore the Baltic Sea back to health and secure a more sustainable future for this critical and beloved natural resource that sustains us all.

What we recommend

Take action

Want to do something about bottom trawling in the Baltic Sea?

Read

Read the full bottom trawling report to learn more about bottom trawling impacts, the issues facing the Baltic and dive into the science behind this story map.

Share

Share this story map on social media and tag the fisheries and environmental ministers in your country to put pressure on them to act! Click on the top right corner of the story map to share the story on Twitter, Facebook and to copy the URL.

Learn

Visit our WWF Baltic Ecoregion Programme website to learn more about the Baltic Sea and the issues that we work on.

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References and Supporting Information

This Story Map is part of the WWF Baltic Ecoregion Programme report:  A sea under pressure: Bottom trawling impact in the Baltic , that serves as a call to action to Baltic Ministers and European Commission to intensify efforts of achieving Good Environmental Status of marine ecosystems in order to support a sustainable blue economy including sustainable fisheries. The report and story map was made possible thanks to a substantial contribution of funds from Monika Selkman, and technically supported by  GRID-Arendal . This Story Map was produced by Louise Lieberknecht, Georgios Fylakis, Màrk Aguera, Torben Dedring, Hannah Griffiths Berggren, Valerie de Leidekerke and Ottilia Thoreson.

Cover Video:

Tim Askew / Shutterstock

Biodiversity slideshow:

○ Grey seal: Ola Jennersten / WWF-Sweden

How Seafood is Caught: Bottom Trawling, Youtube video:

Seafood watch

Benthic Trawl, Vimeo video:

BalticSea2020 and Folke Ryden Production , Stockholm University

Bottom Trawl, Vimeo video:

Stockholm University

SLU sediment, Youtube video:

Clare Bradshaw / Stockholm University / Swedish University of Agricultural Sciences

Photo slider:

○ Angler with large cod: Erik Eriksson

Photo of Côte Bleue, France: 

Ocean Great Ideas

Isle of Arran, Scotland:

○ Photo:  Clydecoast  / Wikipedia Commons shared under  CC BY-SA 3.0 

Underwater photo from Öresund, Denmark

Carlos Minguell, OCEANA

Photo

Fabio Badalamenti

Infographics

1. Baltic sea globe

Spatial data disclaimer

The spatial data on the story map was derived from  HELCOM . MPA boundaries were derived from  ProtectedPlanet  ,  legislation.gov.uk ,  INPN ,  ICES  and  GreenPeace . Author is not liable for positioning inaccuracies, subsequent updates, errors, or omissions of data.

Citation

WWF-Baltic and GRID-Arendal, 2020. A sea under pressure: Bottom trawling impacts in the Baltic. A Story Map developed for the WWF Baltic Ecoregion Programme. Link:  url.grida.no/balticbottomtrawling 

Published Date

28 September 2020