Pilchard Shoals in South-west Australia

Abstract

The distribution of pilchard shoals from echo-sounder records, obtained on the Fisheries Research Vessel Warreen between Albany and Esperance, is described. Data from echograms and ring net catches are used to estimate the density of fish in shoals. A method of estimating the number of shoals of pilchards per acre has been developed, using the sounder as a surveying instrument, and the quantity of shoal pilchards on two parts of the coast has been calculated. Dispersal of shoals when feeding conditions are good is deduced after examination of pilchard stomachs and N70 tow net hauls. Movements along the coast are inferred from the distance shoals must travel to obtain a full feed. The selection and avoidance of certain classes of food are discussed. The manner in which shoals come to the surface is described, and observations are made on behaviour of fish in surface shoals.