Survival of stocked barramundi, Lates calcarifer (Bloch), in a coastal river system in far northern Queensland, Australia

Abstract

As part of an ongoing study to investigate the efficacy and cost-benefit 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 1993. All stocked barramundi were marked with coded wire tags to allow their discrimination from naturally recruited fish and to allow subsequent determination of fish size, release site, and release year class. The initial experimental design used two size classes of fish (30–40 mm and 50–60 mm total length), which were released into freshwater, estuarine and upper tidal habitats. The stocked barramundi took about three years to reach the minimum legal size of 580 mm total length. Stocked fish comprised about 20% of barramundi from the relevant size classes in research catches. No significant difference was found in the numbers of fish returned from the two different stocking size classes. Most stocked fish (62%) were recaptured within 3 km of their release site, but 38% undertook intrariverine movements of up to 37 km. Angler record cards and commercial catch data are being used in an effort to detect measurable increases in catch per unit effort in the recreational and commercial fishery sectors. Cost-benefit analysis indicates that less than 1% of stocked barramundi need to be recaptured to cover the costs of the stocking program.