Monitoring of the salmon and trout stocks in the Tornionjoki river system in 2009

The report assembles the monitoring results for salmon and trout stocks in the Tornionjoki river system in 2009. The main methods of data collection were electrofishing, smolt trapping, Dual-frequency IDentification SONar (DIDSON), compilation of catch statistics, compilation of catch samples and fish tagging.

The average density of one-summer-old salmon parr (age group 0+) along the main river was 16.3 individuals/100 m2. This is lower density than in the previous year, but clearly higher than the average density prevailing in this decade. The average density of older parr (age groups >0+) increased slightly from the previous year and was a new record (14.4 individuals/ 100 m2). A combined analysis of smolt trapping results and parr density estimates indicates a salmon smolt run from the Tornionjoki river system in 2009 of 1.3 million wild smolts. Smolt abundance has been monitored since the late 1980s, with the level of one million smolts only being exceeded in 2008 and 2009.

In 2009 about 7,400 fishermen bought the ‘yhteislupa’ fishing licence. This is an increase of one thousand fishermen compared to the previous year. The Finnish salmon catch in the river system was 31,100 kg (4,700 individuals) in 2009, which is a drop to slightly more than half compared to the catch in 2008. Salmon that smolted in 2007, i.e. two-sea-winter fi sh, dominated in the river catch. The average weight of the caught salmon was 6.4 kg.

The 2009 salmon spawning run into the river was assessed to be 33,000–35,000 individuals. Salmon migration was monitored by so-called DIDSON sonars. This was the first year of monitoring and the resulting uncertain run estimate may need to be revised once more sonar information is gathered.

The natural reproduction of trout has declined in the Tornionjoki river system and the status of the trout populations is unstable. On occasion, no 0+ trout parr whatsoever are observed in some tributaries. Average densities of wild 0+ trout in each spawning tributary monitored were, however, somewhat higher in 2009 than in the previous year. Female sea trout typically mature after three winters in the sea. However, the majority of the sea catch consists of feeding trout on their fi rst or second year. Consequently, few females survive to spawning.

A collection of tables and fi gures presents the monitoring data in detail (in English) and this is available on the FGFRI website: http://www.rktl.fi/english/fish/fish_resources/atlantic_salmon_and/

.