Not threatened or endangered. Tolerant of wide range of temperatures: 9-35°C. Two distinct genetic strains: Fitzroy/Dawson or Southern (better for growth in aquaculture) and Northern. DISTRIBUTION: Found in Australia and New Guinea. Native to northern Australia. HABITS: Prefer slow moving water, heavy vegetation and other forms of in-stream cover. Carnivore that eats fish, crustaceans and insects. Larvae feed on zooplankton. SPAWNING: Sexually dimorphic during breeding season. Spawns in late spring and early summer in southern hemisphere (October to February). Each female can produce up to 200,000 eggs (mean of 43,130) every two weeks at temperatures above 25°C. Females can spawn up to 10 times per season, beginning when temperatures reach 24°C for 3 consecutive days and continue until water temperature drops below 23˚C. Female lays sheet of adhesive eggs during early morning hours, usually on underside of structure (log, roots, rock). Males guard and fan eggs until hatching, a period of 3 to 7 days depending on temperature. Egg agitation is necessary for hatching, and eggs must be constantly aerated when hatching in aquaria. Larvae begin extraneous feeding after 2-5 days on zooplankton ranging from 100 to 250 μm. Low survival rate of larvae (<30%) and do not respond to artificial feed (Artemia). GROWTH: Maximum size of 900 mm total length (nearly 36 inches), and over 3.25 kg (7.15 lbs). Higher growth rates and survival in tanks vs. ponds. Pond growth is slow compared to other tropical species (only 20% of fish exceeding 150 grams in 14 months), but cage and tank growth is much higher (100% over 300 grams in 14 months; 30% over 600 grams). Males have slower growth. USES: Good for angling, food fish and aquarium species. CULTURE: Must be stocked at densities of 50-150 kg/m3. At high densities aggressive interactions decreased significantly during feeding. Tolerant of handling stress at temperatures above 18°C. Can be feed-trained onto artificial feeds but need high protein diet (like barramundi). Not a good species for pond culture because it is territorial and cannibalistic. Recirculation systems work best for culture. Feed conversion rate ranges from 0.68 to 1.38. Need low fat diets (<5%). MARKETABILITY: Highly prized flesh (“best eating quality of all Australian freshwater fish”), doesn’t develop off-flavor. One of Asia’s highest priced freshwater fish. High survival when shipping fingerlings because they lay still and use little oxygen. Prices can be above $40 per kg, but are generally AU$26-28 per kg in Australia. Preferred market size is 400-600 g (0.9-1.3 lbs) in Australia. REFERENCES: Ausyfish Pty. Ltd. 2006. Sleepy Cod Oxyeleotris lineolatus. Available: http://www.ausyfish.com/sleepycod.htm (March 2007). Herbert, Brett, Peter Graham, and Scott Foster. 2003. Effects of added shelter and stocking density on growth of sleepy cod Oxyeleotris lineolatus in ponds. Journal of the World Aquaculture Society, Vol.34(4) 433-440. Herbert, Brett and Peter Graham. 2004a. Breeding and fecundity of the endemic Australian gudgeon, sleepy cod Oxyeleotris lineolatus (Steindachner 1867) (Eleotridae). Aquaculture 236: 241-252. Herbert, Brett and Peter Graham. 2004. Freshwater species - evaluation of sleepy cod and golden perch for aquaculture. The State of Queensland (Department of Primary Industries and Fisheries) 1995 – 2007. Available: http://www2.dpi.qld.gov.au/far/9209.html (March 2007). Native Fish Australia. 2006. Sleepy Cod. Available: http://www.nativefish.asn.au/sleepycod.html (March 2007). |
