Galaxias maculatus is a small diadromous fish found in Australia, New Zealand, South America and on some oceanic islands. Two hypotheses have been advanced to explain this widespread, disjunct distribution. McDowall promoted dispersal through the sea of salt-tolerant juveniles but Rosen and others claimed that the distribution reflected the break-up of Gondwana and subsequent drift of the southern continents. Allozyrne electrophoresis of muscle extracts of specimens of Galaxias maculatus from eastern and western Australia, New Zealand and Chile was used to test the hypothesis that populations of G. maculatus from the western Pacific and the eastern Pacific do not differ genetically. FST based on allele frequencies and genotypes was 0.14, suggesting only minor differentiation between eastern and western Pacific populations. Minor differentiation in allele frequency existed at some loci, but no fixation of alternative alleles has occurred. The populations examined appear to be part of the same gene pool, indicating that gene flow via dispersal through the sea occurs today. It is unlikely that South American and Australasian populations would be conspecific if they have exchanged no migrants since the break-up of Gondwana at the end of the Mesozoic.

Previous studies of the genus Atherinomorus suggested that A. lacunosus was one species with a very wide range over the Indian and Pacific Oceans. Morphology (including osteology) and meristics of many populations of Atherinornorus were studied to test this hypothesis. The results indicate that there are two species pairs of Atherinomorus around the coast of Australia. Each of the four species can be distinguished by the combination of meristic and morphological characters. This study was supplemented with an electrophoretic analysis on a limited collection of fish from the western, northern and eastern coasts of Australia.

The systematics of southern Australian marine and estuarine atherinids has been confused by the many generic name changes since Richardson first described Atherina hepsetoides in 1843. Recent studies have shown that Atherinason esox (Klunzinger 1872) comprises two distinct species. Further studies using electrophoretic techniques have also shown that these two species belong in a new genus rather than in the genus Atherinason. The new genus Kestratherina will therefore include K. esox and a new species, K. brevirostris. Electrophoresis has also shown that Atherinosoma is not a cohesive group, and the two species originally assigned to that genus, A. presbyteroides (Richardson 1843) and A. wallacei, Prince, Ivantsoff and Potter 1982, must be placed into a new genus, Leptatherina.seagrass detritus, phytoplankton, diatoms, bacteria, zooplankton, fatty acids, sterols, fatty alcohols.