XX.—Quantitative Studies on the Invertebrate Fauna of Sandy and Stony Substrates in the River Endrick, Scotland

Synopsis Monthly quantitative samples of the invertebrate fauna were taken from two stations in the River Endrick over a period of fifteen months; the substrate at one station in the lower reaches was sandy, whilst that at the other in the middle reaches was stony. The fauna at these stations differed qualitatively, but showed certain quantitative similarities, especially with regard to seasonal change. The fauna of stones is richer, and much more varied than that of sand, though both substrates appear to be unstable and may be drastically affected by spates. The average standing crop of the invertebrate fauna during 1960 was found to be 8 g. per square m. in sand and 16 g. per square m. in stones. Compared with the few other results which are available for rivers elsewhere in the world these figures would indicate that the standing crops of these substrates in the River Endrick are of intermediate richness.