Some of our Odos are Missing

In years past, Arçais, with its interweaving network of variously sized canals together with a few lakes and a larger river, had been one of my favoured locations for hunting odonata (dragonflies and damselflies). The French, by the way, have no fewer than five words for canal, depending for the most part , I think, on size: rigole; bief; canal; conche; fossé.

L. fulva, ArcaisWe’ve had a couple of bicycle rides around the excellently marked tracks marked from and around Arçais and what we’ve found, or rather what we haven’t found, has been a little depressing. Don’t get me wrong, there are dragonflies and damselflies but they appear to be in reduced numbers compared to years previous. June is the height of the season and in my view they should be here in good numbers. The campsite has a couple of water ways literally just outside its main gate and I have seen good numbers of Orange Featherlegs (Platycnemis acutipennis) on these but now there we found hardly anything. I did see these together with a handful of Blue Featherlegs (Platycnemis pennipes) and a Blue Chaser (Libellula fulva) beside the canal below our friends’ road but again, not in the numbers I’d expect. One of the lakes we knew also seemed to have a reduced population.

Our second cycle route took us through the Marais to the Sèvre Niortaise and we rode along its northern bank back down to Damvix, which is where we used to stay before the campsite owner there went en retraite [retired] and before discovering the site at Arçais – we saw just a handful of Blue Featherlegs at one particular bridge, though I admit the weather was not at its brightest.

Oxygastra curtisii, ArcaisThere is a small pond in the centre of our campsite on which, at first attempt, we found a very few damselflies only. On our second visit, in brighter conditions, we did find one, and only one, dragonfly but oh what a find it was. This was only my second ever encounter with an Orange-spotted Emerald (Oxygastra curtisii) so, though it was alone, I was thrilled. It flew tirelessly, though and didn’t settle so I had to try to capture it in flight. This is a particularly interesting species for me and Britain. It used to occur in the UK at two rivers in Devon and at one site in Dorset. However, it became locally extinct in 1963, contributory causes being thought to be increased sewage pollution in the rivers and the particularly severe winter of ‘62/’63. With sewage and rivers a currently high profile issue, will we never learn?

Our friend Mike thinks there’s nothing wrong here in Arçais. He, however, has been living here every year and if there has been a gradual decline, he may have become accustomed to it as it happened. With two separate snapshots eight years apart, to us things look a little different and the change seems quite marked.

The water in the marais has been cleaned up with no sewage now being dumped into it. We certainly saw no evidence of any duckweed whereas in the past we’ve seen water courses literally covered with the stuff. This is why it is known as the Venice Verte. So, I do not think it’s water quality that may be an issue. I honestly don’t know what’s going on; apparently the fish population has increased so perhaps there is more fish predation?

Posted in 2023-06 France

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