June, 2011

After being sited in Alstersälven for 14 days, the migration trap is still awaiting its first catch. The only thing caught so far, is leeches! However, we should be patient, as perhaps the first catch is just around the corner. Who knows..

After heavy rainfall on Monday night, the water level in Alstersälven rose an incredible 30cm. The knock on effect of the forceful water, and wooden debris  have pounded the trap which is currently ‘riding out the storm’. Certainly not favourable conditions for trapping as you can see from the comparisons of figures 1 and 2.

Figure 1: Optimal and typical water level in the summer months in Alster.

Figure 2: Indicating the concerning increase in water volume and velocity around the trapping site.

Hopefully the water level will quickly subside to enable a realistic chance of catching some eel elvers!

/Joe

I dag kom  vårat papper om avledning av öringsmolt i Emån ut i tidsskriften Ecological Engineering! Ni kan kan läsa abstract för artikeln på tidsskriftens hemsida (klicka här!). Artikeln presenterades vid förra sommarens konferens i Barcelona och inom kort kommer även pappret om nedströmspassage i ätran ut på samma tidsskrift.  Ta en titt på alla biologins papper på nrrv.se genom att klicka här!

Inget regn men en ål ändå. Skärhultsbäcken har levererat ännu en ål. Annars har dagen gått i snickrandets tecken. Själva fällan i Östra Frölunda blir klar i morgon, bara sumpen kvar som skall dit under helgen. Vi vill rikta ett stort tack till dig på Köinge lantmän som lyckades leta upp en rengjord sump åt oss med en mängd telefonsamtal. Kommer inte ihåg namnet i skrivandets stund men du vet själv vem jag menar. Kranarna på yngelledaren är bortskruvade och skall ersättas med nya icke läckande så fort nya kan inköpas, det är ju röd dag i morgon. Fortsättning följer.

What have we found!?
 
-75 fish total of which 35 were eels ( 3 not analysed for weight/length).
 
-Currently 8 other species including mört, braxen, abborre, benlöja, gös, lake, suttare och björkna.  
 
-Biggest eel 1.64kg / 987mm on 22 May.
 
Total eel numbers with different trap treatment:
 
Ytan bara: –>2 stk ( +3stk non analysed)
 
Botten bara: –>11 stk
 
Ytan+botten:  Ytan –> 3stk
                     Botten –> 16stk
 
 
So for the month of May, we have a total of 27 eels in bottom trap and 5 in Ytan. The most likely scenario to catch eels when both top and bottom are open, and then the bottom trap is most productive.
 
However this statistic could easily change within a matter of days since the difference is so minimal!

I have also taken a couple of other pictures of the nature at Alsterälven. The first picture is of a newly emerged dragonfly, clinging onto some vegetation in preparation to dry its wings in the sun to enter adulthood.

Just above is a another sun basker – a snok which has settled just above my upstream migration trap!

Joe