Use constraints: Data can be used freely given that the source is cited (following creative commons license CC-BY). The source should be cited as: “HELCOM HOLAS 3 Dataset (2023)"

In total, data was available from 240 sites in about 120 streams and rivers for period 2012-2014. ICES subdivisions 21 to 32 are represented. At least ten sites are included from each of the ICES sub-divisions 25, 27,

30, 31 and 32.

The Baltic assessment model focuses on the state of recruitment, which is defined as the observed

recruitment (i.e. observed densities) compared to the potential reference recruitment (i.e. maximal densities

that could be expected under the given habitat conditions). The model uses electrofishing data of the

individual sea trout populations, together with habitat information collected at the same sites, to calculate

the trend in population development over time. The examination of the data is site-specific (several sites can

exist in one river) but the evaluation of the state of the stock can be concluded on the river level and also at

a sub-area level. Average values of recruitment state are calculated for assessment areas, sub-divisions, and,

where more countries have streams in one sub-division, for each individual countries (ICES 2011; ICES 2017).

At the annual meetings of the International Council for the Exploration of the Seas Baltic Salmon and Trout

Assessment Working Group (ICES WGBAST), all available data from the Baltic countries on estimated

abundance of sea trout parr (per 100 m2

) from individual sites are compiled. In 2017, data was available from

a total of 257 sites in about 132 streams, which reflects the general situation of data availability.

Additional information:

http://www.helcom.fi/baltic-sea-trends/indicators/abundance-of-sea-trout-spawners-and-parr/

Link to metadata of dataset used for indicator calculation:

https://metadata.helcom.fi/geonetwork/srv/eng/catalog.search#/metadata/e9fc9873-edb9-487d-b76c-350fe5bd2b96