Feshie inverts

Yesterday Michael sorted through the invertebrate sample collected from the Feshie. The Feshie is quite different in character to the other parts of the Spey catchment where we have sampled the invertebrates. The Feshie runs directly from the Cairngorms, water chemistry, temperature and flow regime will be quite different to the mainstem or lower tributaries such as the Livet for example. I expected the invertebrate sample to be of lesser abundance and that is what we found.

Invertebrate sample site in the Feshie at Tolvah. The sample was taken from the riffle/glide just upstream of the ford

Invertebrate sample site in the Feshie at Tolvah. The sample was taken from the riffle/glide just upstream of the ford.

Whilst collecting the sample it was immediately obvious that there was not the same quantity of organic debris trapped within the cobbles and it was virtually silt free, as a result the sample was relatively easy to sort through.

Lower Feshie invert sample. Clockwise from top left: Caddis; stoneflies; mayflies; diptera and others bottom left.

Lower Feshie invert sample. Clockwise from top left: Caddis; stoneflies; mayflies; diptera and others bottom left. The long thread like thing in the bottom left dish is a Horsehair worm. Juvenile horsehair worms are parasitic on invertebrates but the adults are free living. The first time I saw one I wasn’t sure if it was living or not but they do move slowly. Any salmon fishers will know what 20lb maxima is, horsehair worms look just like a short length of brown nylon – watch them, they move.

In comparison to the samples from the Spey mainstem and the Livet the invertebrate population in the Feshie was relatively sparse. The total abundance was 295 individuals. The BMWP score was 95 but the Average Score per Taxa (ASPT) was 7.3, the highest from any of our sites so far. So there were few individuals but they were high scoring, i.e. species sensitive to pollution.

Feshie invert sample graph. Numerically the sample was dominated by a single cased caddis species - Grannom. There were fewer stoneflies than I expected but the mayfly dish contained 15 Electrogena lateralis, or Dusky yellowsteak, the first we have noted ion the Spey.

Feshie invert sample graph. Numerically the sample was dominated by a single cased caddis species  – Brachycentrus subnublis or the Grannom which comprised over half the total. There were fewer stoneflies than I expected but the mayfly dish contained 15 Electrogena lateralis, otherwise known as the Dusky Yellowsteak, the first we have noted in the Spey.

Incidentally I noted the same small caddis on the rocks in the Spey at Knockando the other evening. The riverbed rocks were absolutely covered with very small grannom cases, the big hatch experienced a few weeks ago must have resulted in a huge recruitment of juveniles. If they survive it looks like there could be another big hatch next spring.

We will continue to collect samples from across the catchment and at the end of the summer I will show all the photos showing the sorted samples in the dishes for comparison. It should be clear that the invertebrate productivity of the Feshie is naturally much lower than the Livet; its the same for the salmon fry and parr.

 

 

 

There are 2 comments for this article
  1. Iain hall at 11:57 am

    More fishery boards should publish this sort of data. All too often we appear to focus on fish population rather than the link between the fish and their food chain! Keep up this great stuff. The more we can connect water quality, food chain and fish numbers we may better understand what the devil is actually going on in the sadly depleted salmon populations around Scotland.
    Best regards from a concerned but passionate angler
    Iain

    • Brian Shaw Author at 7:31 pm

      Couldn’t agree more Iain. SEPA have vastly reduced their invertebrate monitoring network so there will be an ongoing requirement for use to extend our coverage. We have a student who is very keen on this aspect but unfortunately he is only here until mid September, however I will try and extract a few more sample analysis before he goes.
      Brian

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