Range extensions for four estuarine gobies (Pisces : Gobiidae) in southern Australia: Historically overlooked native taxa or recent arrivals?

Abstract

Targeted sampling for gobiid fishes in the Port River estuarine system adjacent to Adelaide, South Australia, identified four previously unrecorded species. Significant range extensions along the east-west coastline of southern Australia are reported for the Australian endemic flatback mangrove goby Mugilogobius platynotus (Günther, 1861), largemouth goby Redigobius macrostoma (Günther, 1861) and Krefft's frill goby Bathygobius kreffti (Steindachner, 1866) plus the alien Trident goby Tridentiger trigonocephalus (Gill, 1859). Moreover, M. platynotus, R. macrostoma and T. trigonocephalus are new records to the fish fauna of the state of South Australia. While it is clear that T. trigonocephalus has invaded another southern Australian port, there is difficulty in determining the status of the three Australian endemics as being either native to the area or recent introductions (e.g. through ship mediated translocation) due to a previous paucity of sampling and the cryptic nature of goby behaviour that may have prevented historic detection. The long-term existence of suitable habitat on the one hand suggests that these populations are naturally occurring in the Port River. However, a drastically altered estuarine environment, the high incidence of other translocated marine organisms in the system and goby biological traits suiting transportation in ship ballasts or hull fouling conversely casts doubts over their origin. Contrasting management scenarios of conservation versus potential eradication for these newly discovered species highlights a dilemma for biodiversity conservation in an altered environment.