SURVIVAL OF STOCKED BARRAMUNDI, LATES-CALCARIFER (BLOCH), IN A COASTAL RIVER SYSTEM IN FAR NORTHERN QUEENSLAND, AUSTRALIA

As part of an ongoing study to investigate the efficacy and cost-benef it ratio of stock enhancement of barramundi, Lates calcarifer (Bloch), in coastal river systems, about 69,000 fingerlings have been released into the Johnstone River in northern Queensland, Australia, since 199 3. All stocked barramundi were marked with coded wire tags to allow th eir discrimination from naturally recruited fish and to allow subseque nt determination of fish size, release site, and release year class. T he initial experimental design used two size classes of fish (30-40 mm and 50-60 mm total length), which were released into freshwater, estu arine and upper tidal habitats. The stocked barramundi took about thre e years to reach the minimum legal size of 580 mm total length. Stocke d fish comprised about 20% of barramundi from the relevant size classe s in research catches. No significant difference was found in the numb ers of fish returned from the two different stocking size classes. Mos t stocked fish (62%) were recaptured within 3 km of their release site , but 38% undertook intrariverine movements of up to 37 km. Angler rec ord cards and commercial catch data are being used in an effort to det ect measurable increases in catch per unit effort in the recreational and commercial fishery sectors. Cost-benefit analysis indicates that l ess than 1% of stocked barramundi need to be recaptured to cover the c osts of the stocking program.