The surprise of our life on Mackerel Lake stream!
The third location for our invertebrate sampling is Mackerel Lake stream, a section upstream from the culvert on The Lacques. At first sight this did not look a promising location to find invertebrates, the flow was slow, the water level low and there were long sections choked with water weeds such as dropwort, figwort and watercress, amongst others, as well as being overgrown with brambles. Our little band of volunteers braved the thorns and risk of entanglement to enter anyway to assess what was there; good science isn’t entirely risk free it seems!
It was as we feared, the water level was so low it was difficult to place our nets more than 5cm below the surface and the kick sampling process yielded far more stones and gravel than we were used to. Nonetheless, we persevered and carried out the process to completion with full scientific rigour. We didn’t see very much in our nets as we emptied them into the sample buckets, though the usual freshwater shrimp were clearly jumping about in numbers. We were, however, fortunate to see some bugs burrowing into the stream bed at the end of our survey as we let the waters settle before climbing out. Fascinating as this was, we had finished our survey so trying to capture these invertebrates would have invalidated the protocols to which we are working.
Having transferred our netted samples to the sample buckets we then transported them to a secluded location for the count; we considered it unsafe to carry out this part of the process by the stream side, as we would do normally, due to the risk from traffic on The Lacques.
We carefully transferred the samples to the counting trays and started to search through for the important indicator species. Sadly, on this occasion, no fish, no elvers and no eels. Happily though, and somewhat surprisingly, we found examples of all the Riverfly indicator species including the highly prized Mayfly larvae.
The Mayfly larvae (order Ephemeroptera) is at the pinnacle of clean water indicator species and its presence demonstrates that Mackerel Lake stream is indeed very much alive and kicking. They will live up to three years in this larval phase of their lifecycle before transitioning into the adult Mayfly that we are all more familiar with. They are important indicators as they show that the water is clean, unpolluted and oxygen rich.
Table of the indicator species in full:
Location: Mackerel Lake stream (SN 29878 10794 to SN 29823 10812) | |
Date: 21st September 2026 | Time: 13:00 to 15:30 |
Group | Count |
Cased Caddis | 100 |
Caseless Caddis | 13 |
Mayfly | 6 |
Blue winged Olive | 20 |
Flat bodied Stone fly | 54 |
Olive | 11 |
Stonefly | 43 |
Freshwater shrimp | >500 |
In addition we found 4 small unidentified nymphs, numerous leeches and a variety of aquatic worms. Previously on this stretch of stream a grey heron has been seen, most recently on the 20th September, a grey wagtail is often present and small fish (7cm – 8cm in length), probably brown trout, have been seen from time to time by several people.
In conclusion, Mackerel Lake stream managed to surprise us all with the best haul of invertebrates we’ve seen from our sampling exercises so far. The stream is currently in very good health and we will continue to monitor next year now as, importantly, the sampling season finishes on the 30th of September to allow for fish spawning to take place undisturbed.
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