Persons sorting fish — Sorting herring at sea – collecting key data on fish stocks. Photo: Peter Wickström

Data collection within DCF

Page reviewed: 11/06/2025

How much herring is there in the sea, and how many salmon spawn in the rivers? How do we know if fishing is sustainable? The answer starts with data. Within the EU, vast amounts of information about fish and fishing are collected to inform the union's common fisheries policy.

The Data Collection Framework (DCF) is the structure for coordinated data collection. In Sweden, the Swedish Agency for Marine and Water Management (HaV) is responsible for implementing and coordinating the national programme, which is 60% funded by the European Maritime, Fisheries and Aquaculture Fund (EMFAF). Read more about DCF and Sweden's national programme and annual reports within DCF on HaV's website.

From field to advice – the Department of Aquatic Resource's role in DCF

The practical data collection within DCF in Sweden is largely carried out by the Department of Aquatic Resources (SLU Aqua). The work spans from leading offshore expeditions with SLU's research vessel Svea to analysing fish age and sex in the laboratory. All data collection follows internationally standardised methods, making the results comparable over time and between countries.

SLU Aqua is also responsible for storing, quality-assuring, and analysing the collected data. The information is delivered to recipients such as the International Council for the Exploration of the Sea (ICES) and the EU's Scientific, Technical and Economic Committee for Fisheries (STECF), where our experts also participate in the analysis work. The result is scientific advice on how much can be fished without endangering the long-term survival of the stocks—advice that forms the basis for the EU's annual decisions on fishing quotas. (Link to the page "From data collection to quota decisions")

DCF data is also used in other types of knowledge bases that support management decisions, such as within national fish management. The collected data is further used in research to deepen knowledge about fish stocks, climate impact, and changes in ecosystems.

Where knowledge begins – out in the field

SLU Aqua's data collection within DCF takes place in many different ways and locations—at sea, along coastlines, and in our rivers.

From fishing boats and harbours

A large part of the data comes from the commercial fishery and the logbooks of professional fishermen. To collect biological information on the entire catch—that is, both the part that is landed and the part that is discarded—our samplers regularly accompany the vessels. Sampling also takes place on landed catches in harbours.

Our on-board and harbour sampling is largely carried out on board commercial fishing vessels. We sample all species caught by individual fisheries.

Harbour sampling

Port sampling is a relatively simple way to collect data. Here we focus on the most commercially important fish and shellfish species and we collect data on length, age, weight and in some cases also spawning maturity. We sample approximately 200 fish per thousand tonnes of fish landed.

On-board sampling

As well as sampling landed fish, we also go out on commercial fishing vessels to record data on discards of both fish and other marine life.

Logbooks from commercial fishermen

We also use data that commercial fishermen leave in their fishing logbooks, including the amount of fish landed. We can also calculate the time spent on catching the fish.

Data from our on-board and harbour sampling

Data from our on-board and harbour sampling is stored in SLU Aqua's database Fiskdata2 (FD2). The database contains mostly data from collection within our larger environmental monitoring programs of fish and shellfish, but our goal is to add data from smaller projects as well.

FD2 is not an open database but data can be made available upon request to registrator@slu.se.

Fishery-independent surveys at sea

To gain an independent picture of the stocks, we conduct regular surveys in the Baltic Sea, the North Sea, the Skagerrak Strait and the Kattegat Bay with the research vessel Svea. We trawl at fixed stations and use acoustic methods to estimate how much fish is in the sea. We also film along the seabed to estimate the number of norway lobsters. Read more about our internationally coordinated Svea expeditions.

Data collection on salmon and eel

To monitor the development of salmon and eel, we collect data in so-called index rivers, where migrating fish are counted using sonar technology or cameras, and emigrating fish are captured, counted, and tagged in locally adapted traps. Read more about our data collection on salmon.

New questions require new types of data

As new questions arise about the sea and fishing, data collection also develops. Today, it's not just about counting fish—we also collect genetic data, images, videos, and traces of DNA directly from the water. At the same time, technology is making great strides, with new ways to collect data and smarter ways to analyse it, such as using AI.

Data on nationally managed species

The EU's Common Fisheries Policy—and DCF—mainly covers fishing at sea and commercially important species like herring, cod, salmon, eel, and norway lobster. However, SLU Aqua also collects data and provides advice on species that are nationally managed, such as perch, pike, and pikeperch along our coasts, and in the five large lakes: Vänern, Vättern, Mälaren, Hjälmaren, and Storsjön.