Smolt traps update 12th May

A quick update on the Avon and Tommore Burn traps. Firstly the Tommore where catches have dried up almost completely this week, although we did get a fin clipped salmon today, the first for a week.

Salmnon smolt catches in the Tommore Burn trap related to the water level at 9am. The recent higher water evets have not produced many more salmon.

Salmon smolt catches in the Tommore Burn trap related to the water level. The recent higher water events have not produced many more salmon.

Same graph but showing water temperature along wiht the salmon catch.

Same graph but showing water temperature along with the salmon catch. The absence of any sustained periods of warm weather are apparent. Normally by mid May the temperature could be expected to be routinely above 8oC.

On the Avon the recent higher water levels have not produced big catches of smolts either. Daily catches at present are 50-100 although with the catch efficiency less than 10% there are still decent numbers of smolts moving every night. However, it is now evident that the run, as expected, will be significantly lower than that recorded in 2014. To date we have caught 4,448 salmon in the traps compared to 13,971 in 2014. As mentioned above the capture efficiency is lower this year so that will close the gap a little when we plug all the figures into the run estimate equations.

Avon traps salmon catch and river level.

Avon traps salmon catch and river level.

Avon smolt traps salmon catch and water temperature.

Avon smolt traps salmon catch and water temperature.

The trout catch is also lower than last year but not to the same extent; we may yet end up with total catch figures close to that achieved in 2014.

Avon traps trout catch and river height.

Avon traps trout catch and river height.

One feaure this year has been the number of eels caught in the Avon traps. I think we have caught 17 so far, considerably higher than last year. A possibly explanation is that the eel population seems to be suffering from a disease problem this spring. Both eels caught in the traps today had damage; one on its flank and the head of the other was in a terrible condition.

Lesion on flank of eel captured in the trap today.

Lesion on flank of eel captured in the trap today. Note this is not trap damage but a symptom of some condition affecting eels this spring.

This poor eel had no skih left on its head. Whatever is affecting these eels is obviously changing their behaviour as the botm hugging eels are not normally caught in the smolt traps.

This poor eel had no skin left on its head. Whatever is affecting these eels is obviously changing their behaviour as the bottom hugging eels are not normally caught in the smolt traps.

The Dee Trust have identified a similar problem on the Dee and samples have been sent to Marine Scotland for analysis. The results are awaited. It is a shame to see any animal suffering in this way but sometimes events like these occur. Having spoken to several ghillies it is clear that the problem is widespread across the river.

 

There are 2 comments for this article
  1. Mr mM Fraser at 1:11 pm

    It seems a rise of 15 to 25 mm brings them on .
    I don’t really think temp is a major factor though .
    More to do with the sun and or moon is my guess .. (day,night light hours )
    I helped at the Fiddich site .Was a fantastic learning experience ..

    • Brian Shaw Author at 2:45 pm

      Hi Mr Fraser, you are right in that a only small rise in water level is required to get them moving but temperature is undoubtedly a factor. We have noted that the peak of the smolt run can vary by three weeks depending on the weather and the recent study by Marine Scotland Science showed that the trend in peak migration time had become earlier by 7 to 14 days over the last few decades. Daylength etc has not changed so there must be other factors. The Avon salmon smolts graph shows that the highest daily catch occurred the night after the first morning when the temperature exceeded 8oC.
      Glad you enjoyed the Fiddich work, a lovely burn up there, so much nicer than the Deveron!
      Best regards
      Brian

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