Distribution and abundance of seabirds in Western Port, Victoria

Abstract

The distribution, abundance and biomass of seabirds in Western Port, Victoria, were surveyed between April 1991 and August 1994. Individuals were counted along an 81-km series of transects from a boat at approximately monthly intervals. A total of 25 seabird taxa were recorded, of which 18 and 15 were common to those recorded by an earlier study in Port Phillip Bay and waters south of Phillip Island, respectively. The most numerous species by far was the Short-tailed Shearwater (Puffinus tenuirostris) followed by the Silver Gull (Larus novaehollandiae), Little Penguin (Eudyptula minor) and Crested Tern (Sterna bergii). Distribution within Western Port was not uniform, with pursuit divers such as cormorant and grebe species being recorded mostly in the shallow Eastern Arm. In contrast, surface-seizing (e.g. albatrosses), surface-plunging (e.g. Crested Terns), shallow-plunging (Australasian Gannet, Morus serrator) and pursuit-plunging (e.g. shearwaters) species predominated in the deeper Western Arm of Western Port. These species were also seasonally abundant, with peak numbers for most occurring in late summer–early autumn, which coincides with the reported influx of juvenile clupeoid fish into Western Port. Average biomass (686 ± 395 kg) comprised mostly Short-tailed Shearwaters, Little Penguins and Pied Cormorants (Phalacrocorax varius). Biomass density (8.5 kg km^–2) was similar to that reported for Port Phillip Bay (8.1 kg km^–2) but lower than off the southern coast of Phillip Island (9.9 kg km^–2).