Freshwater jellyfish in France.

This summer we experienced a very long period of drought and two scorching heat waves which are probably the reason for an unusual and little known phenomenon to occur in the Vienne departement along with other parts of west and southwest France! These were exactly the right conditions when the water warms sufficiently for the emergence of a tiny freshwater jellyfish, craspedacusta sowerbii.  

They are normally only seen when they take the form of a small bell-shaped jellyfish known as a hydromedusa and float near the surface of the water but this requires a water temperature of at least 25°C and forms only one part of their interesting lifecycle.

As a jellyfish they are 20–25 mm in diameter, somewhat flatter than a hemisphere, and very delicate. They have a whorl of up to 400 tentacles tightly packed around the bell margin. Hanging down from the center of the inside of the bell is a large stomach structure called a manubrium, with a mouth-opening and four frilly lips. Food is taken in and waste  expelled through the mouth opening.

Click photo to enlarge

Craspedacusta sowerbyi more often exist as microscopic podocysts (dormant "resting bodies"), frustules (larvae produced asexually by budding), planulae (larvae produced sexually by the hydromedusae), or as sessile polyps, which attach to stable surfaces and can form colonies consisting of two to four individuals and measuring 5 to 8 mm.

This species, originally from China (Yangtze River Basin), probably originally arrived in Europe with aquatic plants imported for botanical gardens. In the ponds of Kew Gardens, near London, it was discovered in 1880 by the naturalist William Sowerby. Since then, it has conquered every continent thanks to the trade in aquarium plants.

In France they can be found in slow moving rivers, lakes and ponds, maybe even your garden pond if they have been transported there with pond plants or stuck to birds’ feet.  Should you come across them you need not worry, they present no danger to humans or other mammals.

Chris

An Aesculapian snake fell in the river today.

Having injured my back which has put a temporary halt to all strenuous activity and as it’s been 31°C this afternoon I thought I’d have a wander by the River Charente just to the east of Civray where I could mooch about in the shade of the trees and see what, if anything, turned up or just being lazy in other words, something I'm quite experienced in.

The river Charente has had Asian Hornets almost since they arrived in France as they appeared to follow the river and the tall poplar tree plantations that board the river have provided ideal places for them to make their nests. With this in mind it was no surprise to see some flying around by the riverside but my interest was taken by the fact that they were taking nectar from Water Figwort and stopped to take a few photos, or rather try to as they wouldn't stay still.  

Click on photos to enlarge.

It’s worth mentioning at this point that the River Charente is a very clean river in the upper reaches, it positively heaves with a variety of fish which is great for the Otters! Carp, chub, roach, perch, pike, bream and barbell abound and there are plenty of large mature specimens along with large shoals of fry so it’s not unusual to hear and see the occasional large splash. So it was at this point while looking at the Asian Hornets that there was a large splash about 10 metres from the bank in front of me and then a snakes head emerged from the water and it started to swim towards me. Now for some people I can imagine this isn't their idea of fun but for me it’s always a real treat and I immediately froze so as not to frighten it away and waited as it slithered up the bank and into a hazel bush on the riverside. It didn't dawn on me immediately that the snake had actually fallen from an overhanging branch and I was expecting a “water snake”, either a Grass snake or a Viperine snake and was surprised to see that it was in fact an Aesculapian snake about 70cm or so in length, beautiful! They are frequently found alongside water courses and only a few weeks ago I had seen one dead in the road near the centre of town not far from the river. For anyone that doesn't know Aesculapian snakes are generally timid, slow moving and with care quite approachable which enabled me to get nice and close for the next 10 minutes while it meandered its way round the small branches before eventually sliding away along the bank side. They and the Western whip snake are climbing snakes and both spend time in trees and bushes where they can sometimes take young birds. They will both spend time in peoples roofs as well where shed skins can sometimes be found.

Click on photos to enlarge.

Aesculapian Snake

Asian Hornet

Viperine Snake

Grass Snake

Chris

On the trail of Otters and Beavers in La Vienne

20 years or so ago it would have been impossible to find an Otter or Beaver in any of the rivers and waterways of the Vienne department of France, in fact the Otter was almost pushed to extinction in France and was only to be found in the Atlantic regions and the Massif Central by the 1980’s . Since then there has been a steady improvement with a continuous re-colonisation inland towards the east following the main river systems and their tributaries. In the Vienne department we have the rivers Charente which enters the sea near Rochefort and the Vienne which is a tributary of the river Loire. Both of these rivers also have numerous tributaries notably in the Vienne these are the Clain and the Gartempe which again have their tributaries.

The situation with Beavers is somewhat different following their extinction in most of France with reintroduction being required in many places.

The only river in Poitou Charentes where a reintroduction was attempted was the Creuse in Vienne where 4 beavers were released during 1970-1973 and this failed but this wasn’t the end for our region. During the period 1974-1976 13 beavers were released in the river Loir in Loir-et-Cher and during 1994-1996 another 13 were released in the river Loir in Loir both being successful. From the river Loir the Beavers have bred and slowly increased their range and are now present for us in the rivers Vienne, Creuse, Gartempe, Anglin, Salleron, Clain, Thouet, Argenton and la Dive du Nord.

One of the many tasks undertaken by the recognised Nature Associations along with the ONCFS (Office National de la Chasse et de la Faune Sauvage) is to research and monitor the presence and range expansion of both species and in the Vienne there are several days of research dedicated to this in most years by Vienne Nature along with a small number of volunteers. This requires the relatively simple practice of seeking out signs of their respective activity.

For European Beaver this is dam creation, small tree felling and small gnawed or stripped pieces of branch with their distinctive chiseling patterns.

For Otters it is spraints, (otter excrement), footprints and remains of prey, crayfish claws, fish heads and frogs/toads that have had their insides eaten. Great care needs to be taken with the remains of prey that could result from other activity, anglers in the case of fish and crayfish remains and also Polecat, (Poutois), for Crayfish and frog and toad remains.  Generally frog and toad remains, (known as “carnage”), should not be taken as concrete proof but are a good indication when spraints have also been found within a few kilometres.

With this in mind I set out with Miguel Gailledrat of Vienne Nature the other week for a day on the Boivre a small river that rises in Vasles, Deux-Sevres and enters the river Clain in Poitiers. Its name La Boivre is thought to be derived from the ancient French word Bièvre for Beaver and is today also called Rivière aux castors or “beaver river” although there is no evidence that Beavers were ever here and it wasn't Beavers we were looking for in this river but Otters although it's quite probable that they will colonise the Boivre in time.

I should mention that although the principle purpose was to look for signs of otters we would also record any signs of Coypu, Southern Water Vole and any freshwater clams or mussels and indeed anything else noteworthy but not plants although I’ve included a few photos! The idea is to look at all the bridges and ideally look for 150 metres or more either side of the river on both sides of the bridge if this is possible which unfortunately it often isn’t. When only one side of the river is accessible the use of field glasses may assist in viewing any flat surfaces on the opposite bank.

Click images to enlarge.

The Boivre is the last river in the Vienne dapartement where no signs of otters have been recorded and we were hopeful that we could change that and complete the map and remarkably the very first bridge visited produced spraints on the concrete re-enforcements on both sides of the river – what a great start to the day!

The rest of the day continued with some success with more spraints at different locations, one really fresh! Also found in three locations were toad and frog carcasses, plenty of traces of wild boar and roe deer, coypu excrement and some freshwater mussel, (Potomida littoralis), but for me another important and interesting discovery was some Southern water vole, (Arvicola sapidus), excrement on some rocks by a bridge, a protected species which is being recorded Nationally.

The situation with the Beaver in the river Clain is that traces of activity have been found in the northern part of Poitiers and it’s hoped that they will move through the city and out to the south.

Otter in France

European Beaver in France

Southern Water Vole in France

Chris

Freshwater Clams and Mussels

It may be 2013 but here in La France Profonde there are still shops that close for 2 hours or even more at lunch time. Then when they open you may well wonder why you bothered waiting because in many instances they don’t actually have what you want or perhaps they have it but it’s 5 times the price you can buy it for from the UK.

Anyway, before I start moaning the point is that I spent about 45 minutes poking around by the river Charente near to Civray waiting for a shop to open. This wasn’t likely to be exciting in mid December but you never know what may turn up and it’s a lovely river. The alternative for killing time would be to look at Estate Agents windows or wander round LIDL and even I’m not that sad.

It’s a spot near a sluice where there are always one or two Grey Wagtails,  Motacilla cinerea, (note to self to have a look for nesting activity in Spring-time), and sure enough there was one there on the bank-side – always a welcome sight. The river here can be quite varied in nature, extremely fast flowing following heavy or prolonged rainfall or be almost as still as a lake during dry spells. 

Above - looking upstream.

Location of the river site just below the "v" in Civraisien.

On these upper reaches of the River Charente there are numerous weirs / sluices that obstruct the free movement of both boats and fish so I was somewhat surprised to discover large collections of shells in the shallows and some on the land as well. Of course shells in themselves wouldn’t be a particular surprise but these were Corbicula fluminea, the Asian Clam. First detected in France around 1980 they feed primarily on phytoplankton (algae), which they filter from the sandy or muddy bottom of streams, lakes, or canals. They self fertilise and somewhat scarily can produce between 34,500 and 47,500 individuals in a season, hence within 20 years they had colonised most French rivers, some lakes and a large number of canals. Along with various human means of being spread it seems likely they are transported when very small by being stuck to birds’ feet.

They will be taken for food by Musk rats, (another introduced nuisance species), and possibly by some birds although this would be unlikely in most river situations. Musk rats also take native species of freshwater mussels / clams as can be seen by these other shells in the photo below of what I think possibly are Potomida littoralis, Mulette des rivières., one of the more common river mussel species in western France.

The freshwater mussel begins life as a tiny larva, measuring just 0.6 to 0.7 mm long, which is ejected into the water from an adult mussel in a mass along with one to four million others. This remarkable event takes place over just one to two days, sometime between July and September. The larvae, known as glochidia, resemble tiny mussels, but their minute shells are held open until they snap shut on a suitable host. The host of the mussel larvae are juvenile fish. The chances of a larva encountering a suitable fish are very low and most will die. Attached to the gills of a fish, the glochidia live and grow in this oxygen-rich environment until the following May or June, when they drop off. The juvenile must land on clean gravely or sandy substrates if it is to successfully grow. Attached to the substrate, juvenile freshwater mussels typically burrow themselves completely into the sand or gravel, while adults are generally found with a third of their shell exposed. Should they become dislodged, freshwater pearl mussels can rebury themselves, and are also capable of moving slowly across sandy sediments, using their large, muscular foot.

Life cycle freshwater mussels

Freshwater Molluscan Shells / European pearly mussels

Charente river and tributaries. 

Asian Clam - Corbiculafluminea

Chris