Data collection on salmon

Page reviewed:  22/05/2025

We collect data on salmon which in turn provides the basis for analyses of salmon stocks and research on salmon. The goal is for Sweden to have long-term sustainable fisheries management based on scientific assessments of the size of the fished stocks.

To enable scientific assessments, we annually collect data on salmon and trout. We do this on behalf of the EU and as part of the national data collection programme (DCF – Data Collection Framework).

We collect the following data

  • Fisheries statistics from commercial and recreational fishing
  • Biological parameters such as salmon age, length, weight, and sex
  • Number of smolts (young salmon) and spawning salmon in selected rivers

How the data collection is carried out

Today, commercial salmon fishing in the Baltic Sea consists of coastal fishing using fixed gear. On the Swedish west coast, there has been no commercial salmon fishing since 2015.

The following data are collected from commercial fishing:

  • Catch data for landed and discarded fish
  • Number of fishing efforts and catch per fishing effort
  • Catch statistics in terms of number and size of fish


The following biological data are collected during fisheries sampling:

  • Length
  • Weight
  • Age
  • Sex
  • Scale samples

Fisheries sampling is carried out four times per year with three different fishermen. We measure length and weight for all species caught, and for salmon we also record sex and age.

With the help of genetic analyses of scale samples, we determine:

  • The composition of catches by different salmon stocks,
  • The proportion of wild versus farmed salmon in the catch (this can also be obtained from scale reading)

All fishing that is not commercial, carried out mainly with rod and line along the coast and in rivers is we referr to as recreational fishery. However, fixed gear may also be used.

The following data are collected from recreational fishing:

  • Catch per effort (questionnaire survey)
  • Catch statistics, including number, size, and species
  • Gear inventory (also includes fixed gear used in commercial fishing)
  • Catches from trolling fishing

As part of this section, we also collect data from broodstock fishing in the Dalälven River (Älvkarleby) and the Umeälven River (Norrfors).

We also collect data on all life stages of salmon in a few selected rivers.

Selected rivers

  • Ume/Vindelälven River
  • Testeboån River
  • Mörrumsån River
  • Ätran/Högvadsån River

The following data are collected from the selected rivers

  • Number of upstream migrating spawning fish
  • Density of salmon and trout juveniles (parr) in nursery habitats
  • Number of downstream migrating salmon and trout juveniles (smolt)

In addition to the selected rivers, we also collect data on all life stages of salmon in two additional rivers. Here, we monitor the salmon for a few years at a time before moving to another river. We also monitor one river with a focus on trout.

The purpose of the selected rivers is to:

  • Gather information about the relationship between the number of spawning fish and reproduction, which can then be used for other rivers
  • Increase knowledge about wild salmon stocks
  • Improve the data basis for ICES stock assessments

How we estimate salmon stocks in the rivers

The methods to estimate the number of upstream spawning fish, parr and downstream smolt vary between the rivers. When the salmon migrate from the sea up the rivers to spawn, we count the number of spawning fish in several ways, for example by filming with cameras or tracking fish with sonar in fish ladders or over rivers. We also identify individual fish using, for example, PIT tags (passive integrated transponder; an electronic glass transponder containing an ID number), which are injected into salmon during the smolt stage. Using this data, we can estimate salmon survival in the sea.

We estimate juvenile salmon production, called parr, by electrofishing in places where salmon grow up. To calculate the number of parr per unit area, we fish according to the Swedish standard for sampling of fish with electricity, surveying a defined stretch of river (called a site). When the salmon juveniles have grown to smolt and migrate out to sea, we catch them in different types of traps. By tagging, releasing and recapturing the smolt, we can evaluate the trap’s catch efficiency and thereby calculate the total smolt migration in the river.

Our collected data is submitted to the International Council for the Exploration of the Sea (ICES). ICES then performs stock assessments and provides biological data and advice to the EU for the Baltic Sea, and to the North Atlantic Salmon Conservation Organization (NASCO) for the Atlantic . This information is used in the annual negotiations on catch quotas for the Baltic Sea and the Atlantic respectively.

Co-funded by the European Union