Monitoring of the salmon and trout stocks in the Tornionjoki river system in 2008

The report assembles the monitoring results of salmon and trout stocks in the Tornionjoki river system in 2008. The main methods of data collection were electrofishing, smolt trapping, collation 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 22.3 individuals/100 m2. This is over two times higher than the average density prevailing during this decade and 1.5 times higher than in previous records for 1998 and 2003. The average density of older parr (age groups >0+) was also a new record (13.4 individuals/100 m2), being about two times higher than the average density prevailing during this decade.

In August 2008, the headwater rivers Lätäseno and Poroeno were sampled using electrofishing in order to study the distribution and densities of salmon parr in the area. The uppermost observation of salmon parr was located over 500 km upstream from the sea and eight kilometres downstream from the headwater lake Porojärvi. However, close to this limit of salmon’s distribution area, parr were sporadic in occurrence and low in number.

A combined analysis of the smolt trapping results and parr density estimates indicates a salmon smolt run of about 1,200,000 wild smolts from the Tornionjoki river system in 2008. Smolt abundance has been monitored since the late 1980’s and, for the first time in the time series, smolt abundance exceeded the level of one million. In the 2000s, the abundance has been consistently higher than in previous decades.

In 2008, the Finnish salmon catch in the river system was 57,000 kg (8,800 individuals), which is a catch that is 2.5 times higher than in 2007. Salmon that smolted in 2004, i.e. 2 seawinter fish, dominated the river catch. The average sea age of salmon was lower in 2008 than in preceding years, which also resulted in a lower average weight for the caught individuals.

The natural reproduction of trout has declined in the Tornionjoki river system during the last five years. In 2008, the average density of wild 0+ trout was lower than in the previous year in each spawning tributary monitored. Occasionally, in some of the tributaries, no 0+ trout parr are observed at all.

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