Denmark’s main shellfish procesor is suffering from shortages of raw material

Fighting on several fronts

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This article was featured in Eurofish Magazine 3 2025.

Denmark’s biggest processor of mussels is suffering from a shortage of raw material that has rendered more than two thirds of its processing capacity redundant. Environment-related restrictions and bureaucracy are among the causes of the situation.

Mussel production in Denmark comes from both capture fisheries and from aquaculture. In the five years to 2023 annual output from capture has been two to four times that of culture. But while production of farmed mussels has increased fairly steadily over the years, that from capture has shrunk from 45,000 tonnes in 2015 to 17,000 tonnes in 2023, a trend that is a source of concern for companies such as Vilsund Blue, a processor of mussels based in Nykøbing Mors on the Limfjord in Jutland.

Lack of mussels has led to consolidation in the industry

Jan Christensen, COO of Vilsund Blue, says the falling production has meant a steep drop in the raw material the company needs. As a result, from five companies involved in mussel processing 25 years ago, there is today just one, Vilsund Blue, and that too is operating at only 30% of its capacity. Part of the issue is restrictions introduced to mitigate the impacts of climate change. These have meant that only 28% of the Limfjord is available to fish mussels and only at certain depths, the rest is designated a nature protected area. The depth restrictions also contribute to the falling catches and the lack of raw materials, says Mr Christensen. The mussels live at depths of between 3 and 8-9 m but for the last couple of years we have been prohibited from fishing at depths less than 5.6 m.

Mr Christensen feels that the mussel fishing industry is being made a scapegoat. Danish waters are under pressure from nutrient run-off from agriculture and from inadequately treated sewage, however mussel dredgers and the plumes of sand they generate are highly visible, so they make an easy target for restrictions. But, he says, the dredgers operate in areas where there is little or no vegetation because that is where the mussels are. They are not found in highly vegetated areas, they are present on sand banks. That there are three ministries with a voice in the administration of the activity probably also leads to differences of opinion with the sector. In addition, further complications may arise if there are divergences between the estimations of the two scientific institutions that are involved in assessing the sector and its environmental impact. Driving the whole process is EU legislation, such as the habitats directive and the water framework directive, that Denmark is obliged to follow. Mr Christensen is also frustrated at the slow processing of cases at the agency responsible for issuing fishing licences. If it takes a month or two to issue a licence it means our supply of raw materials is also delayed by the same period and we are then unable to fulfil the contractual obligations we have with big companies across Europe which leads to fines, reputational damage and, most threatening of all, the takeover of our markets by non-EU players from countries where standards are looser than ours.

Discussions in the shellfish committee are muted

A forum to discuss these issues exists in the form of the shellfish committee which brings together representatives from the ministries, agencies, research establishment, industry, and NGOs. However, Mr Christensen complains that the character of these meetings, which are held roughly twice a year, has changed. Instead of discussing things as a group as we did in the past, the meetings are now used to inform us of what is planned, what has been done, and what has been decided. The agenda of the last meeting, he says, had a single point for discussion, the rest were for information. The implication seems to be that environmental considerations outweigh other aspects of the fishery, and that the industry must learn to live with conditions it does not like. Henrik Nielsen, who heads Foreningen Muslingeerhvervet, the mussel industry’s representative body, concurs. The numerous NGOs in the shellfish committee tend to drown out the voice of the industry, he feels, with the result that neither the challenges facing the industry nor the potential solutions get discussed.

Dredging may not be the most environmentally friendly way of fishing, but it is legal and highly regulated. It is the main method used to fish mussels and other shellfish in the Limfjord. Cockles and mussels are fished with a dredge, the frame of which may not weigh more than 50 kg and may not have a width of more than 1.5 m. Vessels typically use two dredges on either side of the vessel. However, oyster dredges are limited to a weight 35 kg and a width of 1 m, and a vessel may only have a single dredge on either side. In a 2024 report on the status of the shellfish fishery in the Limfjord, Jens K. Pedersen, a professor at DTU Aqua and director of the Danish Shellfish Centre in Nykøbing Mors, notes that there are restrictions in the form of closed areas in the Limfjord as well as a minimum depth of over 4 m to protect eelgrass beds. Eelgrass takes a long time to re-establish if disturbed and is an important indicator of ecological status, so areas with eelgrass are out of bounds for mussel dredging. Together with Vilsund Blue, Alex Mikkelsen, an entrepreneur, owns Seafood Limfjord, a company that farms mussels on longlines in the Limfjord. He acknowledges the importance of protecting eelgrass but, he says, there is virtually no eelgrass in the Limfjord, so excluding large tracts from mussel farming or fishing is unlikely to serve any eelgrass conservation purpose. He is particularly concerned about ideas to create a 100 m buffer zone which, if implemented, could affect up to a quarter of his lines. According to Mr Nielsen eelgrass-related restrictions cover not only existing beds but also areas where the plant could potentially grow. But, he says, this potential will not be realised as long as nutrients from agriculture and untreated sewage continue to enter the ­Limfjord. The industry is thus being ­penalised for no fault of its own.

Spatial restrictions are supplemented with other limitations that restrain the capacity of the motors and the size of the boats and limit the catch to 45 tonnes per week per licence. As a bycatch, cockles may not exceed 49% of the total catch. Temporal restrictions prohibit fishing at night until an hour before daybreak. Moreover, all vessels shall be equipped with a black box (which monitors location, speed, and if the dredges are active) and those above 15 m shall have AIS (automatic identification system). Logbooks are mandatory and for vessels above 12 m they must be electronic. Catches must be reported before the vessel arrives in port. Activity in Natura 2000 areas must be reported before the trip starts and there are limitations on the number of vessels that can fish simultaneously in these areas. Calculations based on data from the black boxes and the logbooks show that since 2016 when dredging affected 49 sq. km in the Limfjord, the operating area has decreased to 29 sq. km in 2023, while the number of times an area is dredged increased from 2.4 to 3.1 over the same period. The Limfjord is some 1,500 sq. km in total so, as Mr Christensen points out, the fishery affects about 2% of the area.

Growing and harvesting mussels also have favourable environmental impacts

A further argument in favour of harvesting the mussels is that if they are not taken, they will simply disappear over time. To get a fresh crop of mussels we need to remove the old ones, Mr ­Christensen states, citing research studying a test bed in the Limfjord that had supported a mussel fishery for a quarter century and was left untouched in the experiment. Today the bed is just sand, he says, without a single mussel. In a 2019 paper, researchers from the Iwona Rakowska Maritime Institute of Gdańsk mention several ecosystem services that mussel farms provide including reducing the nutrient load in the water, increasing biodiversity by creating habitats for algae and small animals, reducing turbidity, binding CO₂ when building their shells, in addition to providing food and feed. Ensuring the presence of mussels may therefore be desirable even if it entails dredging. On-bottom mussel ­production through relaying could be a way of increasing productivity of mussel beds, reducing the impact of dredging, and, by removing mussels from eutrophic areas where they may die to ­oxygenated waters, secures the resource. In a 2018 paper, Prof. Pedersen and colleagues report that the ratio of net biomass of relayed to ­harvested mussels was close to 1:1 in general, suggesting no increase in productivity. The main ­problem was predation by starfish. The authors proposed that although relaying may not increase net biomass it may limit the impact of dredging as fishers search for mussels on commercial mussel beds as well as enable mussels to survive ­oxygen depleted or heavily predated areas. 

The impact of dredging on the ecosystem varies depending on the seabed, but its intensity depends on several factors including the dredge number and dimensions, the environmental conditions of the area, including plant and animal life, the type of sediment, water depth, and currents. In their 2024 report, Prof. Pedersen and his colleagues point to several studies conducted by DTU Aqua investigating the impact of mussel dredges on bottom fauna. The studies do not provide an unequivocal ­conclusion regarding the impacts of dredging. Effects could be seen on some indicators for bottom fauna such as biomass, but they were ambiguous. Nor was there an explicit impact of dredging on the Water Framework Directive bottom fauna indicator DKI (Danish Quality Index). This is not to say that dredging has no effect, but that estimating the effect is complicated by other stress factors such as the flow of nutrients into the Limfjord and their impacts. In general, dredges impact the seabed more than other gears, but because the distances dredged when fishing for mussels are short, mussel dredging is considered relatively less harmful than when dredging for other species. Dredging and washing the shellfish both increase the turbidity of the water due to the suspension of sand particles, but DTU Aqua estimates that this effect is inconsequential in the Limfjord. Another issue facing parts of the Limfjord is eutrophication, which is caused by nutrients leaching into the water from land and increasing plant and algae growth. This in turn leads to low-oxygen conditions in the water when they die and decompose. Mussel fishing has little impact on low-oxygen levels as the worst period is in July and August when mussel fishing is prohibited. According to DTU Aqua, dredging’s release of nutrients from the seabed that can contribute to plankton growth and thus to hypoxic conditions is limited and transient. In fact, dredging can reduce the threat of hypoxia by removing mussels that would otherwise contribute to it. 

Mussel processing, a zero-waste activity

Producing mussels in Denmark is positive for the environment if the alternative is to import mussels from Latin America or even from other European countries, Mr Christensen points out. In the Limfjord operations there is virtually no transport as the Vilsund Blue processing factory is so close to the fishing grounds. The fishing trips are short, so diesel consumption is low—in fact a proposed new tax on diesel (later withdrawn) would have had almost no impact on mussel fishers because they use little fuel. The company makes use of the entire mussel, and even the water used to cook the shellfish is used as a source of nutrients and tastes, so there is no waste. The empty shells have different uses; cockles are crushed and used as filters to purify air, while mussels are used in building materials and in horse tracks, among other applications. The small amount of marine snails and other organisms that the company receives are also utilised either for biogas or by a Norwegian partner to extract nutrients for animal feed. We have a really good story to tell with so many positive aspects, but it is completely torpedoed by this discussion on the impacts of dredging, says Mr Christensen with some irritation. Mussel fishers would be the last to damage the environment in the Limfjord, points out Henrik Nielsen from Foreningen Muslingeerhvervet, as it would ultimately affect their business. They already go the extra mile by, for example, fishing only nine months in the year and taking only 15 tonnes per week instead of the 45 tonnes their licences permit, he adds.

Several events conspire to hit the industry

The mussel fishing season usually runs from October to June, with the three remaining months being used to carry out maintenance work and to send staff on vacation. However, last season the fishing only started at the end of February instead of the preceding October making it a very expensive year for the company. The threat from Latin America affects ­mussel ­producers across Europe, but some of them have interests in the Latin American industry and thus benefit from exports to Europe. Moreover, mussels from some European producers, such as the Dutch, have a very high meat-to-shell ratio and are less affected by imported mussels. These differences mean that some producers, like Vilsund Blue, are more vulnerable than others to the threat of substitution from imported mussels. Finally, the war in Ukraine has diverted mussels destined for markets there and in Russia to other markets in Europe, so we’ve been hit by a perfect storm of events in the last couple of years, Mr Christensen declares. While he agrees measures to preserve the Limfjord are also in the company’s interest, he finds that the debate has become more emotional than factual, which could have unfortunate consequences not only for the industry but perhaps for the Limfjord as well.