Neil Loneragan

A method of processing data has been developed to facilitate the storage, retrieval and analysis of data collected during ecological studies of fish populations. This method was also used to compare the composition of the fish community in the shallow water of the Peel-Harvey and Swan-Avon estuaries. A total of 42 species representing 22 families were recorded from the Peel-Harvey compared with 50 species and 28 families in the Swan-Avon. Fifteen species accounted for approximately 95% of the total numbers of fish caught in both estuaries. The most prevalent species in the Peel-Harvey was the marine species, Pelates sexlineatus, whose abundance might be related to the presence of large quantities of Cladophora, which constitutes a major proportion of its diet and which is found throughout much of the Peel Inlet. By contrast, the estuarine species, Nematalosa vlaminghi, was the most abundant species in the Swan-Avon in which it utilised both the riverine regions of the upper estuary and also the broad expanses of water in the middle estuary. Amongst the 15 most abundant species, a greater number were represented by populations capable of completing their entire life cycle within the estuary in the Swan-Avon (9) than in the Peel-Harvey (6). The relative abundance of estuarine species was also higher in the Swan-Avon than in the Peel-Harvey. Species richness decreased through the Peel-Harvey but reached a maximum in the middle estuary of the Swan-Avon.