Prawn hatchery modifications and adaptions for temperate marine fish culture in northern NSW, Australia

Marine fish culture is a new farming opportunity for NSW prawn farmers. To address current seed-stock supply issues two Palmers Island brackish-water prawn hatcheries (of Australian and Taiwanese design) were examined for conversion to mulloway (Argyrosomus japonicus) production. Both hatcheries were easily adapted with minimal cost and modification; the Australian design (1062 m²) was the simplest and cheapest to convert. The Taiwanese design (695 m²), required more work due to the permanent built-in nature of the concrete tanks, their rectangular shape and drainage. Fingerling output from the Australian hatchery was calculated at 630,000 × 40 mm (1 g) fingerlings or 150,000 larger 100 mm (12 g) fingerlings using a single annual hatchery run of 3 or 5 months, respectively, at a water temperature of 20–25 °C. The smaller Taiwanese hatchery had a theoretical maximum production of 320,000 × 40 mm (1 g) per batch or 50,000 × 100 mm (12 g); if pure oxygen was used in the nursery area this could be increased to 100,000 × 100 mm. Both hatcheries could operate with 3 to 4 staff and use of these facilities, in conjunction with staff training, would resolve the current poor availability and high cost of juveniles for grow-out.