Rockpool ichthyofaunas of temperate Australia: species composition, residency and biogeographic patterns

Abstract

This paper provides the first large-scale data of the rockpool ichthyofaunas of southeastern New South Wales (NSW), Australia, and compares the fish assemblage structure of this region with other regions in Australia and the world. A range of studies undertaken between August 1999 and September 2001 at 14 locations yielded 14,225 fish comprising 50 species from 26 families. About 64% of species were endemic to Australia, 30% have an Indo-Pacific distribution, while 6% have a trans-Tasman distribution. The dominant families were Gobiidae (4836 fish, four species), Tripterygiidae (3589 fish, three species) and Clinidae (1672 fish, five species). Permanent rockpool residents comprised 85% of assemblages ( Bathygobius cocosensis, Enneapterygius rufopileus and Lepidoblennius haplodactylus), opportunistic temporary residents comprised 14% ( Girella elevata) and the remaining 1% comprised seasonally abundant transients ( Chaetodon auriga and Kuhlia mugil). Fish assemblages in the present study were similar to other rockpool fish assemblages in northern NSW, although latitudinal variation was evident with a gradual replacement of temperate fishes with those of a tropical origin. On a global scale, Australian rockpools support unique ichthyofaunas but the dominant families (Blenniidae, Tripterygiidae, Gobiidae, Gobiesocidae and Clinidae) are similar to those in many countries of Gondwanan origin, such as Chile, Portugal, New Zealand and particularly South Africa where some species are even shared. Rockpools in countries of Laurasia origin (United States, Mexico, and Canada) support very different fish assemblages mainly representing the families Cottidae, Stichaeidae, Scorpaenidae and Pholidae. This probably represents speciation of rockpool fishes since separation of these landmasses in geological time, which may be driven by limited larval dispersal and colonisation of some species in specific regions.