Abstract

Results of a fish tagging study carried out in the Murray River, South Australia from 1974 to 1978, are presented. Of 14 333 fish tagged, 1276 were recaptured and the records of these recaptures yield evidence on the movements of several species of both commercial and recreational interest. Some golden perch (Macquaria ambigua) migrated extensively upstream, many moving more than 1000 km. The migration followed, and appeared to be triggered by, a rise in water level at the onset of major flooding. The upstream migrations, made only by mature fish, appear to be a reproduction strategy to ensure that the eggs, which are buoyant, are distributed downstream. In contrast, common carp (Cyprinus carpio), which lay adhesive, demersal eggs, did not migrate but made only random, short- distance movements. Although data on other species were fewer due to their smaller populations, it appears that Murray cod (Maccullochella peeli) and catfish (Tandanus tandanus), both of which have demersal eggs, show similar movement patterns to carp whereas silver perch (Bidyanus bidyanus), which lays buoyant eggs, is similar to golden perch. The implications of these results, with regard to the establishment and maintenance of populations of each of the species, are discussed.