Laxräknare - Torneälven – Pajala

Lohenlaskenta – Tornioväylä - Pajala

 

New data is presented 2007-04-18 the data is now processed and recalculated. The numbers is corrected with a factor for horizontally used sonar, the number corrects the fish target strength so we are now able to use the –29 dB  (-29 dB represent a fish 63 cm big (Lilja 2004)) as the limit for salmon and other species. During the summer 2006 the limit was set to –27 dB (fish longer than 80 cm). 

 

In the tables below we present number for down streams moving fish that is calculated as 32% of the fish that is mowing up streams. Witch was the actual number for fish bigger than 80 cm (TS –27dB) during summer 2006.

 

Calculation with the uncovered time and area factors gives us the theoretical maximum numbers of salmon moving upstream.

 

The operating time for the data collecting is 95% from 06-06-12 to 06-09-16

 

The covered area is 70 % of the river.

 

There are still some corrections to do and this will correct the numbers slightly

 

Salmons spotted in the beam bigger than 63 cm

 

 

8663

Theoretical salmon mowing downstream (32,8% of 8663)

 

2842

Salmons moving upstream theoretical minimum

 

 

5821

 

 

 

 

 

 

 

Theoretical salmons moving upstream calculated with time and area factors

12955

Theoretical salmons moving downstream calculated with time and area factors

4250

Salmons moving upstream theoretical maximum

 

 

8705

 

Average size salmon moving upstream calculated from sonar data

86 cm

6,3 kg

Average size salmon calculated from catch reports (Muonio and Kolari fishing areas 2006)

--- cm

7,0 kg

 

 

Fish that is longer than approximately 1,4 m does not exist and is a known error when using sonar horizontally. Some of the fishes are moving so close to another that the sonar cannot differ the fishes from others and appear as on big target in sonar screen. There are also some errors with the tilt of the sonar and the swim directions. This results in that some fish will appear bigger than in reality. The sum of fish, moving upstream, that is bigger than 1,4 m is approximately 400.

 

© CEITAtech 2006