Making ‘Sence’ of the River and her Crustacean Inhabitants


I am lucky enough to have the River Sence run through my edgeland in South Leicestershire (Pictured above). With the presence of water comes a huge variety of added wildlife that you otherwise wouldn’t see in open farmland, edgeland and woodland lacking a waterway. If you have ever created even the smallest of ponds in your garden you will have noticed a significant shift in the range of flora and fauna and witnessed the value added to the mini ecosystem that is your garden.

A river is an altogether larger beast, both in the mass of the water and the range of wildlife that it can bring. Of course not all rivers are created equal – there are no wild Salmon leaping over waterfalls and weirs in the Sence in search of Highland pools for spawning and unfortunately many of our open rivers and waterways around the country have succumbed to pollution in one form or another with the dramatic decline of Water vole and Otter just the TV sound bite tip of the iceberg in the recent decimation of river dependant species.

The River Sence that passes through my patch is a tributary of the River Soar. Rising from two springs in higher ground at Billesdon, East Leicestershire around 18 miles away the river snakes and flows from village to village, passing through my edgeland in Wigston, South Leicestershie and westwards another 5 miles or so to Enderby where it joins the Soar. Confusingly, there is another river Sence in North-West Leicestershire that supplies the Anker but this hasn’t always been the case.

Before the sixteen-hundreds the River Sence flowing through South Leicestershire was recorded on maps as the River Glene, differentiating it from the River Sence in the North-West of the County. Glene is the old Celtic name which means ‘Clean or Holy’ and that still rings true to an extent today.

A couple of weeks ago, standing on the footbridge in warm afternoon sunshine I noticed something moving in the water below me. A Signal Crayfish, given away by its large front pincers displaying a white patch at the claw hinge – like the white flag a signalman used for directing trains, hence the name ‘Signal’ Crayfish – stirred from the river bed and began making it’s way downstream. Crayfish are considered a key indicator species for the health and biodiversity of our rivers and will only thrive in areas with clean, well oxygenated and preferably slightly alkaline water. They cannot tolerate muddy, silty or polluted water. This is a good sign then that the river Sence is indeed ‘Glene’ and has good biodiversity. Unfortunately the presence of this alien invader isn’t all good news.Se

The Signal Crayfish is native to North America and was introduced here in the 1970’s as a food source for the booming restaurant industry. It has since spread throughout England and Wales at a rapid rate leading to an almost complete loss of our native White-Clawed Crayfish through direct competition and the transfer of a disease called Aphanomyces astaci or ‘Crayfish Plague’. Signal Crayfish are resistant to the disease whilst our native White-Clawed variety will succumb within weeks of encountering the spores of the disease which can be spread from waterway to waterway simply by contact, such as on a contaminated wellington boot or fishing tackle. Signal Crayfish can also happily cross land for several miles to reach another water-source making it almost impossible to stop the spread.

Signal Crayfish can have adverse affects elsewhere as well, they are voracious predators that will eat anything in their path including plants, invertebrates, snails, small fish and native, sometimes rare, fish eggs. They have a habit of burrowing chambers into river walls that can extend for over three feet in which they can lay up to 275 eggs, weakening the structure of the bank over time and contributing to collapse and flooding in heavy rain.

As I watch the Signal Crayfish emerge from the other side of the bridge below my feet, I notice another shifting uneasily up-stream. Remarkably this isn’t a Signal at all but the now very rare and endangered White-Clawed crayfish. I have to bend right down to the waters edge to take in the detail and fire up google on my phone to confirm what I have seen. The White-Clawed Crayfish (pictured below – you will notice it doesn’t have white claws except for the underside where the crayfish takes it’s name) has much smaller pincers in comparison to the Signal whose pincers are often as large as the length of its entire body and lacks the invaders ‘Signal’ marks at the base of the claw. Proportionately the White-Clawed Crayfish is generally smaller too although this can be hard to differentiate when compared to Signals of a lesser age. I have read that small pockets do still exist in the Sence and the neighbouring Grand Union canal although I understand that the data gathered on the entirety of the river is minute.


Whilst I am elated, humbled even to have clapped eyes on such a rare crustacean I can’t help but feel uneasy about what the future has in store for her. With the Signal Crayfish passing within inches of her miniature figure whilst I continue watching their movement up and down the riverbed, it is sadly almost a foregone conclusion that at some point in the not too distant future she will succumb to the plague. This 25 mile stretch of blissful, bubbling, clean and otherwise thriving water that I am eternally thankful passes through my edgeland will eventually, almost inevitably lose the White-Clawed Crayfish altogether.


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