Frequently asked questions (FAQs)

1. What is a typical, suitable proximate analysis for the diet for barramundi?

2. What is a typical feed formulation for barramundi diets?

3. What protein level and key amino acid levels should be used in barramundi diets?

Optimal dietary protein content has been shown to vary with dietary energy levels and the size of fish. Most studies suggest a crude protein requirement between 45 percent and 55 percent Requirements for protein and amino acids decreases with increasing fish size according to the change in energy demand of the fish. Some EAA requirements have been determined for L. calcarifer and are provided in detailed in Table 2 of the main text.

4. What plant protein sources and typical inclusion rates can be considered in barramundi diets?

Plant proteins can partially replace fish meal (more detailed information is provided in Table 7 of the main text). Several cereals have been tested and solvent extracted soybean meal (SBM) was shown to support good growth at a 10 percent fishmeal protein replacement level. No palatability problem has been observed with SBM up to a 30 percent inclusion level. Solvent extracted SBM is more palatable than extruded or steamed full fat SBM.
It has been obtained good weight gain and FCR (1.7:1) in fish fed with a combination of fishmeal, shrimp head meal, scrap squid meal, SBM, and kangkong leaf meal as protein sources. Ipil ipil (leucaena) leaf meal can also be used but this may result in a lower FCR. White cowpea and green mung bean meals have been used as protein sources in practical diets at inclusion levels of 18 percent of the diet without affecting growth. Corn gluten meal can be included at up to 10 percent of the diet.

5. What oils are suitable for inclusion in barramundi diets?

It has been have shown that fish oil can be replaced with soybean oil with no effect on growth because of its appropriate ω3:ω6 ratio. Similarly, it has also been reported that partial replacement of fish oils with vegetable oils (soybean, canola and linseed) has no significant effect of the lipid, moisture and protein content of the fish carcass.

6. What vitamin and mineral mixture can I use in my pelleted feed for barramundi?

Certain dietary vitamins have been identified as essential for barramundi. Vitamin C requirement is 500–700 mg/kg of diet or 25–30 mg/kg of diet using crystalline ascorbic acid or ascorbyl-2-monophosphate-magnesium, respectively. It has been have shown that 5 mg/kg diet of pyridoxine was required for normal growth and 10 mg/kg for normal lymphocyte levels. Pantothenic acid requirement is 15 mg/kg diet for normal growth.

Regarding minerals, dietary phosphorus requirement ranges between 0.55 percent and 0.65 percent. The addition of salt to the diet at a level of up to 4 percent has been reported to generate a better feed utilization.

7. Feeding strategy:
What size of feed do I need at different stages, from first-feeding fry to onwards and how frequently should I feed them?

It has been shown that there was no benefit in feeding small fish (40g) more than twice daily, and large fish (>270g) more than once a day, and also feeding time had almost no affect on fish growth. The fish consumed food whenever it was fed, even during the night. During the weaning process feeding time and place should be fixed, and the fish should be attracted by sound to induce them to school to improve the feeding response.
Regarding feeding methods, hand feeding is commonly practiced in ponds and cages where labour cost is low. In Southeast Asia, trash fish/low-value fish is often chopped and broadcasted by hand. Trash fish can either be prepared daily, or refrigerated for later use. In intensive larval culture, live food, pellets and microalgae are fed by hand but automatic feeders are often used to maintain optimum feeding frequencies and to ensure optimal densities of microalgae and live food in the tanks. Drip feeding systems can be used for live food and clockwork-driven belt feeders for pellets. During the hatchery period frequent feeding improves growth and reduces cannibalisms. In larger systems (cages, tanks or ponds) feed blowers, feeding rings or automatic feeders are used to provide the single daily meal.

8. What are the differences between extensive and semi-intensive larval rearing?

Ponds are often used for extensive larval rearing. Production costs are lower and larvae have a faster growth than larvae reared intensively in tanks possibly owing to better nutrition resulting from a more varied diet and to greater natural prey availability throughout the day. A combination of inorganic and organic fertilizers is recommended. The most commonly used fertilizers in Australia are diammonium phosphate and lucerne pellets. Two days after hatching, larvae are stocked at 400 000 to 900 000 fish/ha into the pond.
Regarding intensive techniques, both "clear water" and "green water" rearing techniques are used to rear L. calcarifer. In both techniques, the rearing cycle usually involves the production in succession of Rotifers and Artemia (nauplii and sub-adults), but copepods and cladocerans can also be used and may improve growth and survival. In green water systems, the main phytoplankton species are Nannochloropsis, Tetraselmis and Chlorella sp. stocked at 8–300 cells/µl from 0-1 DPH to 15-21 DPH . First feeding should occur at 48 hours post hatch for optimal growth and survival, but algae and rotifers can be added to the tanks before first feeding (around 36 hours PH).