Abstract
Six stations were sampled 13 times between June 1972 and October 1973. Species taken at any one station on at least 75 % of the sampling dates were considered vital, i.e. as having a complete life cycle at that station. The abundance and biomass of the 20 vital species recorded at the stations are compared to data for the total macrofauna. The distribution of the vital species with respect to environmental parameters is discussed.