Life cycles and distribution of atherinids in the marine and estuarine waters of southern Australia

New and published data have been collated for the biology and distribution of atherinid species abundant in the coastal saline waters of Australia below 30°S. This information has been used to determine whether these species typically spawn at sea or pass through the whole of their life cycle in estuaries, and in one case, also lagoons and saline lakes. Length-frequency data, gonadosomatic indices and distribution records indicate that in south-eastern Australia Craterocephalus honoriae and Atherinosoma microstoma typically reach total lengths less than 90 mm, have a one-year life cycle and breed within estuaries. This parallels the situation recently described for Atherinosoma elongata, Atherinosoma wallacei and Allanetta mugiloides in south-western Australia (Prince et al., 1982a; Prince & Potter, 1983). The marine species Atherinosoma presbyteroides, which reaches a similar size and has a one year life cycle in both south-western and south-eastern mainland Australia, only enters estuaries in large numbers in the former region. While Atherinomorus ogilbyi is also found in estuaries and typically breeds at sea, it reaches total lengths as great as 189 mm and has a longer life than A. presbyteroides. The limited data for Atherinason esox and Atherinason hepsetoides demonstrate that both these marine atherinids can attain total lengths of 139 and 108 mm respectively and live for longer than a year but do not enter estuaries in large numbers. The latter species is unique amongst southern Australian atherinids in having a distribution which extends into deeper water. It is suggested that landlocking may have played a role in the evolution and success of the estuarine mode of life sensu stricto of A. wallacei, A. elongata, A. microstoma, A. honoriae and A. mugiloides in southern Australian waters.