The bottom fauna of a flatfish nursery ground

Abstract

The macrofauna, defined as infauna retained on a ½ mm sieve, was investigated on a flatfish nursery ground at less than 10 m depth in a Scottish westcoast sea loch during spring and late summer of 1965. The substratum consisted of well-sorted sand of 180–260 μ median diameter, and the infauna had a mean density of 755 individuals and biomass of 1·3 g dry weight/m2 on the beach and 3055 individuals and 3·7 g dry weight in the sublittoral. There was little overall change in the biomass during the period studied, increases in amphipods and some polychaetes being balanced by decreases in other polychaetes, and in Tellina for which no recruitment took place. The distribution of the fauna was studied in detail between high-water mark on the beach and a depth of 10 m below low-water springs. There were 62 species on the beach and 116 on the sublittoral sand. The number increased as the water deepened, the poorest zone being just below low-water mark. Most species showed a distinct zonation. The epifauna of the sand, which was dominated by juvenile stages of plaice and dabs, is briefly described