Basin Notes - October 2000

Pearls are Valuable to Fish

This conservation-led project involves a number of agencies, landowners and fishery interests to preserve the fresh-water pearl mussel. This creature M. margaritfera is in serious decline in all Scottish rivers.

Apart from the occasional pearl, these mussels each produce in a day approximately 50 litres of clean water. Being filter feeders they prefer fast-flowing streams and burns and embed in gravel banks.

Salmon parr and trout benefit from their clean water output and they in turn support the pearl mussel, during its life-cycle.

The pearl mussel egg embeds in the gills, living in the oxygen rich environment for about a year before dropping off in another reach of the stream, creating a new colony elsewhere. No harm seems to come to the fish.

The inter-dependence of the young fish and the fresh water pearl mussel may be a factor in the drop in fish numbers. Precious though the pearls maybe, the preservation of these useful creatures is now a serious issue. Pearl fishing is banned.

True countrymen are a rare breed, Not only farm folk and county parsons, the village Bobby on his bike and the village schoolmaster could all be relied on to make some observations on their patch. It might be possible for you to help.

A recent five-year study of butterflies will have two outcomes - the first is the forthcoming "Millennium Atlas of Butterflies" to be published by OUP in March; the second result may be the adoption of the butterfly as an official wildlife indicator, measure of the health of the countryside. Global warming and GM crops can have affects on their spread and ability to breed.

Populations are fragile for a variety of reasons and anything that interferes with their yearly cycle of breeding simply wipes out the population in that area.

A free information pack about recording butterflies is available from Butterfly Conservation, P.O.Box 222 Dedham, Colchester C07 6EY (tel 01206 322 342) or visit their website.

Dune areas, grassland and dry heath from Montrose to St Cyrus as well as cliffs and beach areas are precious for their populations of plants and insects. Glens and quiet upland peat bogs are another excellent source of interesting plants and creatures.

River banks and old railway lines are corridors along which creatures may migrate. If you walk the dog regularly along the same path, that can be your patch - make a note of what is around you.