The low water has allowed me to investigate the state of the invertebrate and other populations in  the river Wye along the Wyebank stretch this April. I should think that water snails, of which there are many species in the river, must be an important element of the fish’s diet, particularly barbel. Every larger stone is currently covered underneath with the gelatinous balls of water snail eggs. The nymphs of the Yellow May dun and Olive Upright are also everywhere and the freshwater shrimp, which was quite scarce a few years ago, is now again more common. Although the shrimp prefers clean water it can tolerate mild levels of pollution and is not the marker of pristine water that it was once thought to be. However the shrimp’s abundance is vital as a food item for fish, particularly salmonids.

Most satisfying is the abundance of swan mussel shells on the raised shoals of the far bank, which are now dry. This is a swan mussel site recorded in SSSI assessment of circa 1996 which by 2006 was virtually devoid of shells. The swan mussel lives in the sandy and silty gravel substrate, so living organisms are not seen. The presence of significant numbers of non eroded shells is indicitive of a healthy population.

Yesterday, Saturday 23rd, two days before St Mark’s day, was marked for me by the largest swarm of hawthorn fly which I have seen for years. Bibio marci, the Hawthorn or St Mark’s Fly due to its occurrence on St Mark’s day, has again been quite scarce in more recent years. As this is a terrestrial fly its abundance or otherwise cannot be blamed on river pollution! At Little Dean, on the eastern edge of the Forest of Dean, where hatches were immense over a decade ago their demise cannot be blamed on spraying as it is traditional dairy farming with little or no spraying of any sort. Whether there will be sufficient winds to blow the hawthorn onto the water to induce a rise of trout, only time will tell.