​​​​​​​Key message

This core indicator evaluates the status of coastal sea areas of the Baltic Sea based on the abundance of sea trout parr in rivers where they breed. The determination of whether Good Environmental Status (GES) is reached is based on a comparison of the observed parr densities in rearing habitats with the reference potential parr densities in the specified habitats. The current evaluation assesses the status of sea trout populations using data from 2014 and expert evaluations.

Key message figure 1_sea_trout_spawners_and_parr.jpg 

Key message figure 1: Status assessment results based evaluation of the indicator 'abundance of sea trout spawners and parr'. The assessment is carried out using Scale 3 HELCOM assessment units (defined in the HELCOM Monitoring and Assessment Strategy Annex 4). Click to enlarge.

The current evaluation shows that the status reflected by populations of sea trout is sub-GES in most Baltic Sea coastal areas. GES is not achieved in the Bothnian Bay, the Bothnian Sea or the Gulf of Finland. A positive development in parr densities since 2012 has been observed in some rivers in Finland (Gulf of Finland), Estonia (Gulf of Finland) and Sweden (Bothnian Sea), reflecting management improvements in these countries.

In the Baltic Proper, the status of sea trout stocks is better in south-western sub-basins where the majority of stocks reach production levels reflecting GES.​

The level of confidence of the assessment is moderate to high.

The indicator is applicable in the rivers of all the countries bordering the Baltic Sea.


The densities of parr measured in rearing areas in rivers reflect the abundance of the adult sea trout spawners and success of recruitment. Adult sea trout carry out feeding migrations in the Baltic Sea where they are top predatory fish.

Sea trout abundance is affected by commercial and recreational fishing at sea and in rivers. The parr densities measured in rivers are affected by migration barriers to reproduction areas and habitat quality. Thus the indicator reflects the state of the ecosystem as it is sensitive to river connectivity (effect of dams) and the quality of spawning and rearing habitats.  

Policy relevance of the core ind​​icator

BSAP segment and objective​s

MSFD descriptor and criteria

Primary link


  • Thriving and balanced communities of plants and animals

  • Viable populations of species

 D1 Biodiversity

1.1 Species distribution
.2 Population size
1.3 Population condition
1.5 Habitat extent

Secondary link

D4 Food-web

4.3 Abundance/distribution of key trophic groups and species

D3 Commercial fish and shellfish

3.1 Level of pressure of the fishing activity
3.2 Reproductive capacity of the stock

​​Other relevant legislation: In some Contracting Parties of HELCOM potentially also EU Water Framework Directive


HELCOM (2015) Abundance of sea trout spawners and parr. HELCOM core indicator report. Online. [Date Viewed], [Web link].

Download full indicator report

Core indicator report – web-based version Octo​ber 2015 (pdf)

Extended core indicator report – outcome of CORESET II project (pdf)