Biology and ecology of the non-indigenous goby Acentrogobius pflaumii (Bleeker 1853) in the Swan-Canning Estuary
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AbstractNon-indigenous species can have significant deleterious impacts on the ecosystems in which they become established. Following the recent establishment of the Striped Sandgoby Acentrogobius pflaumii in the Swan-Canning Estuary, south-western Australia, a study was initiated to determine its spatial and temporal distribution and biological characteristics. Although A. pflaumii was not recorded in the coarse sandy sediment present in the nearshore, shallow waters of the estuary, substantial numbers were recorded on soft muddy sediments in the deeper waters, where it comprised 55% of the total number of gobies. While A. pflaumii dominated the gobiid fauna in Lower Melville Water (~98%), its contributions declined progressively upstream, indicating a preference for waters with a salinity close to that of full strength sea water. Size and age compositions determined that the oldest individual was 3.9 years old and 89 mm in total length, but that the population is dominanted by 1+ individuals. Population mortality and turn-over rates are therefore likely to be very high. Both males and females attained > 87% of their asymptotic lengths (L∞) of 74.9 and 69.3 mm, respectively, during the first year of life, which is characteristic of smaller, shorter-lived species of fish. The results from gonadosomatic indices and the histological examination of gonads suggest that A. pflaumii is able to spawn throughout most of the year, with a peak from November to February. The presence of mature, spawning and depleted gonads in A. pflaumii suggests that this species spawns within the Swan-Canning Estuary. Acentrogobius pflaumii can be thus considered an estuarine & marine species like Favonigobius lateralis. As A. pflaumii attains high densities over a relatively large part of the estuary and can breed within the system, it is likely to be a permanent resident and further work is needed to determine its impact on the native gobiid fauna.