AbstractNine experiments were conducted on the tropical northern Australian
freshwater eel-tailed catfish (Neosilurus ater) to investigate (a) the lipid content and fatty acid profile of the lipids in adult and juvenile catfish, (b) seasonal changes in the physical and chemical characteristics o f the liver and ovary, and the lipid content and fatty acid composition of eggs and larvae, and (c) larval rearing of catfish with Artemia nauplii, formulated and/or zooplankton diets.
The baseline total lipids o f the muscle tissues o f w ild adult eel-tailed catfish
were significantly higher than those in juveniles. The m ajor fatty acids in the lipids of adult muscle tissues were 16:0, 18:0 and 18:ln-9, and the main PUFAs were 20:4n-6 and 22:6n-3. The distribution o f total lipids and some fatty acids in the body of adult catfish were not homogenous but dependent on the horizontal location o f the body. The total lipids of whole fry and muscles of fingerlings were not significantly different and the major fatty acids (16:0, 18:0, 18:ln-9) in the fry and muscles of fingerlings were also similar. The levels o f 20:5n-3 and 22:5n-3 were higher in the fry and smaller stages o f fingerlings.
The resting period and the period of rapid gametogenesis were M arch to
October and November to December, respectively. The total lipid o f the ovary can be used as an indicator o f gametogenesis. The levels o f 18:0, 20:5n-3 and 22:6n-3 increased in the liver and ovary just prior to and during gametogenesis. During larval development, saturated and monounsaturated fatty acid (16:0 and 18:ln-9) levels decreased while levels o f PUFAs (20:4n-6 and 22:6n-3) increased.
Feeding of catfish larvae with Artemia nauplii should not be delayed beyond 3-4 days after hatching to avoid high mortality. During delayed feeding of larvae, PUFA especially 22:6n-3 increased but total lipids and monounsaturated fatty acid levels decreased. Enrichment o f Artemia nauplii with cod liver oil or com oil prior to feeding them to catfish larvae was a successful strategy since the postlarvae had higher survival and growth. Finely ground barramundi pellets were not required during the first 15 days o f larval rearing in a green-water system and in the absence of prepared feeds, the larvae accumulated higher amounts o f PUFA especially 22:6n-3.
|Date of Award||Aug 2000|
|Supervisor||David Parry (Supervisor)|