A couple weeks ago we collected an invertebrate sample from the middle reaches of the Livet; this week a sample was taken from further upstream, well above Tomnavoulin at Allanreid. I haven’t really had a proper look at the Livet in the summer (to be corrected this year) but it was obvious from the coating of phytoplankton (algae) on the rocks that it was chemically richer than many other Spey tributaries. In the faster flowing water there was less algae and an invertebrate sample could be taken without the net becoming clogged with algae.
Plenty fish could be seen in the Livet, but then it is one of the best tributaries of the Spey, the expectation should be to see an abundance of fry and parr in the Livet. At this time of year it can be hard to avoid the fry with the sampling net but we managed to rescue five from the bucket before we headed back to the office so sort through the sample. Michael, one of our summer students did nearly all of the sorting and all the identification. It was obvious that he was regretting showing such an interest in the subject in his first few days as the sorting tray was teaming with life!
By the end of day two the sample was sorted, see picture below.
In total there were over 2800 specimens counted and identified, the most by far that we have found from a Spey site. Invertebrate sampling is quite seasonal as some species hatch others appear. Over 300 Ephemerillidae nymphs (Blue winged Olives) were present, They have only just started to appear in samples as they overwinter in the egg stage. There were over 1200 mayfly nymphs in total and nearly 900 stoneflies, including a few of the large species Perla bipunctata. Caddis flies were less numerous than at the Castle Grant site on the mainstem but there were still over 200.
We scored this sample using the British Monitoring Working Party (BMWP) system, the score being 164. The score at the lower site was 127, combined with much lesser abundance. There could be some sort of impact affecting the Livet further downstream, although both scores were good (generally a score over 100 is considered good).
This sample turned out to be quite a marathon to sort and identify but it does show the productivity of a burn like the Livet. There is a more than ample supply of invertebrate food to support a high juvenile population. Comparing SEPA results from the Livet from the mid 2000s it is clear that we found vastly more in our samples than recorded by SEPA.
All of the samples examined so far have been good, but all have been from the mainstem or productive tributaries, the next one will have to be from a less productive site for comparison.
A big thanks to Michael for sticking with it and sorting this sample. All good experience for your future career!