The Sid Valley Biodiversity Group is engaged in a project to help improve the health of our river.  The group has been carrying out various investigations and surveys to establish the current state of the river before they can plan how to make it even better.  

The Sid and its tributaries have a small population of brown trout but used to be a breeding ground for sea trout and salmon.  There are other fish such as miller’s thumb and brook lampreys, but there appear to be fewer than when the river was last surveyed ten years ago.  

mayfly nymph

One important survey involves the nymphs and larvae of various river flies, particularly mayflies, stoneflies and caddisflies.  These small invertebrates are rather like the canaries once used in coal mines.  If  the canaries stopped singing the miners knew there was a dangerous build up of methane gas.  If there isn’t a healthy population of river flies, we know there is probably something wrong with the river environment.

Volunteers from the Biodiversity Group have been training to carry out scientifically valid surveys of the river fly populations at different parts of our river system, from its various source springs down to The Byes.  

The main activity is to get into the river and disturb the gravel where the fly nymphs and larvae live so they are swept into a net.  There is a standard procedure for how this is done and then the invertebrates are counted to provide data that can be used as a reliable indicator of the river’s health.  All the invertebrates are returned to the river where they quickly dive back down to the safety of the stoney river bed.  There is more about this survey on the Biodiversity Group’s website https://sidvalleybiodiversity.org/.

The good news is that, although not pristine and with a reduced fish population, our river water is reasonably healthy.  The survey sites so far have yielded populations of the eight target species as well as plenty of other species that are not recorded formally.  The issue with some of the fish is more to do with the physical state of the river including barriers such as the school weir.  A migrating sea trout was seen trying to scale the weir recently but it failed.

There is plenty of evidence that local farmers care about the biodiversity of our valley and its river, but one problem they have is run off from fields in the steeper areas of the valley during heavy rain.  This is why the river runs so red, the rain washes soil and soil nutrients into the tributaries and then down to the main river.  This has always happened, but we are tending to have more frequent and heavier bursts of rain and so the problem is becoming worse.

Another branch, pardon the pun, of the project is that the Biodiversity group is teaming up with Sidmouth Arboretum to help landowners restore old hedges and plant new ones near the various head waters.  Apart from providing homes and feeding sites for all sorts of creatures, hedges slow down the run of the water and help keep the soil where it is needed, in the fields.

There are other plans coming together to tackle some of the problems associated with the physical condition of the river but these are more long term and involve bodies such as the Environment Agency.  There will be various consultations with the public and the land owners as these plans crystalise into solid proposals.

In the meantime, if you have the chance sit by the river for a while next summer watch the river flies as they perform their aerial mating dances and hope there will be plenty of nymphs to feed the fish.

Ed Dolphin

Image credits SVBG

SVBG is a not for profit organisation dependant on volunteers, grants and donations.  Without funding we cannot operate and many of our biodiversity projects will cease.

Even the smallest donation can make a difference to wildlife such as the kingfisher on our logo.  

The easiest way to donate a small sum is to click here to Donate

lf you want to give a larger donation, or for a specific project please get in touch via our Contacts page

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