A Quantitative Survey of the Macrobenthos of Western Port, Victoria

Abstract

The results of the first bay-wide quantitative survey of the invertebrate macrobenthos of Westeln Port, Victoria (145º E., 38ºS.) are presented. Three 0.1-m² samples were taken with a Smith- McIntyre grab at each of 41 randomly selected sampling stations, and the results were used to provide both bay-wide and regional estimates of population distribution and abundance.

More than 19 600 individuals were collected, and 572 species identified. The fauna is dominated by polychaetes, crustaceans and molluscs which provided respectively 54.1, 31.7 and 6.6% of the individuals collected and 35.7,47.7 and 10.3 % of the species identified.

Comparison of faunal affinity between stations showed two major faunal assemblages whose distributions are linked with sediment type. These assemblages are a 'clean medium sand' assemblage distributed in the deeper (> 5.5 rn) sublittoral channel areas, and a 'fine sand and mud' assemblage distributed over the tidal flats and in shallow (< 5.5 m) sublittoral areas. Species characteristic of the 'clean medium sand' assemblage are the polychaetes Scoloplos spp. 1-4, Rhodine sp. and Travisia sp. ; the bivalves Neotrigonia margaritacea, Notocallista diemenensis, Solen vaginoides and Venericardia bimaculata; and the crustaceans Halicarcinus rostratus, Ampelisca sp., Cheirighotis megacheles, Leptanthura diemenensis and Paranchialina angusta. Characteristic of the 'fine sand and mud' assemblage are the polychaetes Amaeana sp. and Mediomastus sp.; the bivalves Tellina deltoidalis, T. mariae and Katelysia rhytiphora; and the decapod crustaceans Pontophilus intermedius, Macrobrachium intermedium, Halicarcinus ovatus and Litocheira bispinosa.

A third, minor assemblage was also recognized. This contains the stations nearest to Hastings, the largest centre of urban and industrial development in the bay. The fauna at these stations is impoverished in species and low in species diversity.

Both affinity analyses and survey statistical analyses were applied to the data. The advantages and limitations of each are discussed.