Southern Iron Blue alive and well at Blashford Lakes

Saturday 18th April 2009

The Riverfly Partnership held a workshop at Blashford Lakes for anglers, riverkeepers and others interested in learning techniques for monitoring water quality in our rivers. The method used is to sample to groups of invertebrate present, mostly the larval stages of various flying insects, and to produce a score that indicates the water quality.

There are tens of thousands of anglers out daily along our rivers and they are potentially a great source of data on the quality of our rivers. Fish-kills are easily noted but lesser incidents can eliminate whole groups of invertebrates without any obvious signs that there is anything wrong, monitoring the invertebrates is the key to identifying these incidents. As well as providing water quality information it also offers the chance to find interesting species. The training session produced larval stages of both of the classic stream species of Odonata (dragonflies and damselflies), the Beautiful Demoiselle to the (above right)and a truly huge and rather hairy looking Gold-ringed Dragonfly (below left ).

Although both are fabulous creatures they do not actually feature in the monitoring, this looks at Mayflies, Stoneflies, Caddisflies and freshwater shrimps. Of these the last are the most critical and can be eliminated by even the slightest pollution incidents. Luckily we had no problems finding good numbers of them in the Dockens Water at Blashford along with a wide range of other creatures.

The title of "Find of the Day" went to the mayfly larva pictured to the right, this is Nigrobaetis niger known in English as the Southern Iron Blue. It is one a number of mayfly species found but was by far the rarest being a BAP (Biodiversity Action Plan) species. It is distinctively marked with a long pale stripe down the body and dark bands on each of the three "tails".

All in all it was a great day and I will be setting up two monitoring sites on the Dockens Water shortly.