A survey of the bottom fauna of streams in the Scottish highlands

Abstract

1. A survey of the bottom fauna of 52 streams in the Scottish Highlands was carried out in 1960. The survey included streams on granite (13), schist (16), basalt (6), limestone (7) and sandstone (5). 2. The bottom fauna was much poorer in amount in streams having a concentration of less than 400 µe of total cations/l than in streams having 401–800 µe of total cations/1. In the spring, streams having a concentration of more than 800 µe of total cations/1 were not richer in number of animals than streams with 401–800 µe of total cations/1, and although in the summer the mean number of animals in the streams with more than 800 µe/l was greater than the mean number in streams in the 401–800 µe/l range the increase was of doubtful significance. 3. Granite and schist were the only types of rock having streams with water containing less than 400 µe of total cations/1. The bottom fauna of these chemically poor streams is compared with the fauna from the richer streams (700–1662 µe of total cations/1) on the same rock types. The summed samples from eleven. chemically richer streams contained 11,341 animals and the summed samples from the chemically poor streams contained 3,347 animals. Of the difference of 7,995 animals only 963 or 12% were of species or other taxa not present in the samples from the chemically poor streams. 4. The amount and composition of the bottom fauna from streams on different types of rock and having a concentration of over 400 µe of total cations/l was very similar.