Trawlfiskeri. Foto: Øivind Berg

More sustainable fishing requires combined efforts

Friday 15 Oct 21


Henrik Gislason
DTU Aqua
+45 35 88 33 61

The new report ‘Environmental Friendliness and Ecological Sustainability of Danish Fisheries’ from DTU Aqua shows where there is plenty of room for improvement for fisheries in Danish waters. Read about examples such as how we can make Norway lobster fishing and bottom trawling fishing more environmentally and climate friendly, and about by-catch using gillnets.

The overarching message stemming from the many different results in the new report from DTU Aqua, ‘Environmental Friendliness and Ecological Sustainability of Danish Fisheries’, is that no one initiative is enough to send Denmark into the sustainable ‘premier league’ when it comes to our commercial fishing industry. A combination of efforts are needed in order to make the utilization of the sea’s resources more environmentally friendly and ecologically sustainable in the future. 

Download the DTU Aqua report ‘Environmental Friendliness and Ecological Sustainability of Danish Fisheries’ (in Danish)

From a European standpoint, fishing must be reduced even further. According to the International Council for the Exploration of the Sea (ICES), fishing has halved over the past 20 years. “Nevertheless, fishing is still too intensive to be sustainable for about half of the commercially important stocks caught by Danish fishers (cf. table p. 56),” the report concludes.

For this, measures must be taken, including the development of new fisheries technology, the designation of protected areas, and eco-certification:

More environmentally- and climate-friendly fisheries technology (p. 86). The development of fisheries technology aimed at reducing the physical impact on the seabed, so that the seabed fauna is less affected. You can also target fishing much more accurately using camera technology to see what you are catching, and by doing so, avoid large by-catches (p. 93). You can also reduce the by-catch of porpoises by the use of a ‘pinger’ — a noise transmitter put on the net that can be heard over a large distance by porpoises (p. 91).

CO2 emissions can be minimized by streamlining trawling equipment. And finally, you can avoid ghost equipment — lost fishing equipment that continues to catch fish—and plastic pollution by using biodegradable materials for fishing nets (p. 92).

Protected areas (p. 94). “Our results indicate that it is relatively easy to limit the consequences of bottom trawling without inconveniencing fishers too much — by leaving the areas that are currently not fished much alone,” says Henrik Gislason, Professor Emeritus, DTU Aqua, and one of the main authors behind the report.

In the Danish Maritime Spatial Plan (2021), it has been proposed that 4% of the Danish sea area be completely closed to bottom trawling. But calculations show that if you reduce Danish fishing in the areas that are not already heavily fished, and concentrate on fishing where 90% of the efforts today are, only 19% of the Danish sea area will be affected by fishing with bottom trawlers (p. 97).

Eco-certification (p. 106). MSC and NaturSkånsom labels. Most Danish fisheries are MSC-certified. MSC is an international certification, and the Danish Naturskånsom label was introduced in 2020. MSC promotes ecological sustainability in fisheries. This can been seen by the fact that several fisheries that were previously certified have lost the right to use the label as they no longer met the requirements for sustainability (p. 109). The Naturskånsom label includes coastal fishing. However, neither label covers CO2 emissions, ghost nets or plastic pollution (p. 110).

Themes that call for action

The purpose of the report is to provide a basis for decision-makers to be able to balance the general environmental considerations with the management of fisheries in Denmark.

“Here, the legislators have a lot of the data and information that is needed for sustainable fisheries management, collated in one place,” says Henrik Gislason, Emeritus Professor at DTU Aqua and one of the main authors of the report.

The last time a similar report was drawn up was 2014.

In the new report, 16 contributing researchers systematically review effects on the marine environment and on the climate of various types of fishing equipment and methods used by Danish commercial fishers. It is a complex and multifaceted story—here are some reflections on the themes that call for action:

Discard — the EU’s landing obligation does not work. Fishers have always thrown the part of the catch they did not want back into the sea. This is called discard or re-release. In 2013, the European Commission created the landing obligation, which was to act as an incentive for fishers to avoid by-catching and discarding of quota species, as all catches of quota species including those below the minimum size — with certain exceptions — had to be landed and written off against the quotas. 

According to the report, however, this obligation has not worked as intended (p. 46 ff.) — quite the opposite. Partly as there has been no change in the by-catch landed, and partly as the EU has increased the fishing quotas to accommodate the fact that fishers received lower quotas due to landing obligations — the quota increase has probably only contributed to an even greater death of fish in recent years (p. 55). 

Net fishing results in by-catch of porpoises and birds. A gillnet is passive fishing equipment placed on the seabed. In the debate on fisheries, it is considered to be more environmentally friendly compared to trawling, as it does not drag across the seabed. On the other hand, the new report indicates that net fishing has a considerable by-catch of porpoises and seabirds.

Estimates show that an annual average of 2,750 porpoises drowned in fishing nets in the period 2010–2018 (p. 82). As there are no reliable figures for the porpoise population in Danish waters, it is not possible at present to say whether by-catch mortality has led to a decrease in their population or not.

The Norway lobster fishery in Kattegat is detrimental to the environment and the climate — as is all other food production. But in its current form, it is one of the fisheries that affects both the environment and the climate the most (p. 118). The seabed is affected by the bottom trawling equipment that fishers use to catch Norway lobsters with. The fishing vessels use more fuel per kilogram catch than any other type of fishing (p. 37), and almost half of the catch — primarily non-quota species — is discarded as by-catch (p. 46 ff. and p. 118 ff.).

“It will take time to make fishing more environmentally friendly, but collaborations between researchers and fisheries are underway today with a view to develop more precise and considerate tools,” says Henrik Gislason.

For example, researchers of fisheries technology from DTU Aqua in Hirtshals are working together with fishers to develop tools to reduce by-catch and underwater cameras for trawlers with software that can recognize species of fish and Norway lobster, which together will help to fish much more accurately, with much less impact, the researchers report.

Seabed fauna is bearing the burden. The seabed plays a major role when looking at the impact of fishing on the environment. Bottom-scraping equipment such as trawlers and mussel dredgers naturally affect the seabed in the hunt for lobsters, mussels, flatfish, etc. The seabed is disturbed, and over time becomes rearranged so that it is softer and more uniform, with large stones and grit sinking into the softer bed, and wave ripples on the seabed and banks becoming re-bedded or erased (p. 44).

This will especially leave its mark on deeper water and with intensive use of heavy trawling equipment. The report mentions Kattegat as an example, where many of the larger free-living benthic fauna species have disappeared as Norway lobster fishing has increased (p. 72).
Here, the researchers point out, it would be possible to achieve a more gentle form of fishing by developing and utilizing the new tools and techniques of precision fishing that researchers and fishers are working on together.

Researchers see the coastal areas as a place where we lag far behind in regards to sustainable management. Fishing is being carried out with great intensity, as there is both intensive commercial net fishing and large-scale recreational fishing with nets and traps (p. 35). In 2019, there were 28,000 people who took out fishing licences to fish with nets and traps, and 137,000 licences given to fish with rods.

“As long as we don’t have a precise number on how much recreational, amateur and commercial fishing is taking place locally along the coast, it is difficult to form an overview of the impact of fishing on fish stocks and the environment in coastal Danish sea areas and fjords,” says Henrik Gislason (p. 11).

Much more knowledge about seabed environments is the way forward

The report shows that when you take an aerial view of Denmark, fisheries with trawling equipment actually currently cover a smaller area that you would think when talking about combined fishing in Danish waters (p. 97). On the other hand, there is a difference in the degree of impact:

“This means that 67.5% of the Danish seabed area has not been affected by Danish fisheries with trawling equipment in the past six years. However, if you zoom in on specific types of beds and water areas, there are examples of significantly higher impact percentages due to e.g. deeper mud beds in the Kattegat, where trawling for Norway lobster is intensive, and where only 29.5% of the area is unaffected,” says Ole Ritzau Eigaard, Senior Researcher, DTU Aqua.

“We now know that the first trawl passage has the greatest impact on the seabed. It can therefore be favourable to limit fishing in the areas that are quite easily fished,” says Henrik Gislason.

So the next step towards more environmental friendliness and ecologically-sustainable fisheries management in the future is about understanding the long-term effects from the different fisheries in the different waters on the seabed:

“At present, we in Denmark actually have a very limited knowledge of the benthic fauna, especially in the North Sea and in the Baltic Sea around Bornholm.  We need much more knowledge about the fauna of the seabed if we are really going to have a good basis for assessing the natural resources of the seabed, for example in connection with the new Danish Maritime Spatial Plan,” concludes Henrik Gislason.

The report is compiled from research projects, overview reports and statements to the authorities, and is supported by the Ministry of Food, Agriculture and Fisheries. The report is published today.

Photo: Øivind Berg