The mouth of the flathead grey mullet is open at day 2 and the yolk sac is fully absorbed at day 5. The small size of the eggs (<800 µm diameter) and the relatively short (2 days) yolk utilization period involve to offer very early larval food meeting the nutritional requirements (Harel et al., 1998). Active feeding begins at 70 hours post hatching, prior to full absorption of the yolk sac. Rotifers and microalgae should therefore be offered on day 2. The larvae will die within 192 hours if not fed (Eda et al. 1990).

Size, motility and density of the food items were found to be important factors (Brusle, 1981) but the mouth size and the development stage also affect the larval feeding behaviour. Food sizes fed to mullet fry are usually about 50–75 percent of the mouth diameter (Xu et al., 1985).

Live food should be available to the fish during the whole day and it is recommended to check feed densities at least twice daily. Light intensity affects the feeding behaviour of the larvae and the light intensity at the water surface should be above 500 lux for normal feeding behaviour (Lee and Kelley, 1991).

The food selectivity of Mugil cephalus larvae for rotifers and Artemia nauplii have been studied (Oozeki et al., 1992):

• L-type rotifers should be given to the larvae from day 3 (3.3 mm TL) to day 13 (5.2 mm TL).
• Preference for Artemia nauplii increased from day 3 and was positive from day 13 Artemia nauplii should be added from day 9 (4.3 mm TL) and become the main food when the fish reach 5.0 mm TL.
• Formulated food can be added after the fish are 6.3 mm TL.

Recent larval feeding protocols can be summarized as following: with a larval stocking density ranging between 20–30 larvae/l (up to 40 larvae/ml - Harel et al., 1998), rotifers (preferably of 110–230 µm size) are given at 10–20 individuals/ml during the 25 first days and phytoplankton (preferably Nannochloropsis oculata) is added to the tank during that period. Artemia nauplii are given for the first time at day 12–17 and until day 35 with a density ranging between 0.02 and 3 individuals/ml (Eda et al., 1990; Gautier and Hussenot, 2005; Tamaru et al., 2005) (Table 5).

Live food production guidelines are available in Annex A. Rotifers should be enriched in essential fatty acids in order to meet the flathead grey mullet nutritional requirements. Rotifers are often fed on microalgae (N. oculata). Baker’s yeast can also be used but in addition with microalgae in order to avoid deficiencies in fatty acids (C14, C16, C20:4n-6, C20:5n-3 and C22:6n-3) (Tamaru et al., 1993b). Commercially available enrichment media can also be used for enriching rotifers and artemia.
According to Shcherbina et al. (1988), regarding the feeding of mullet juvenile and larvae,  nauplii of Artemia salina are deficient for methionine (meeting only 38 percent of the requirement), threonine (47 percent), histidine (58 percent) and isoleucine (64 percent) while rotifers, Brachionus plicatilis, are also deficient in methionine (35 percent). Species of prey organism that have not been previously enriched cannot provide an optimal diet, and a combination of several species is desirable.

There is a significant improvement in both larval survival and growth when larvae are reared in the presence of background phytoplankton (Tamaru et al., 1994). This improvement is probably due to the positive effects of phytoplankton on both environmental and nutritional factors providing vitamins and free amino acids to the rearing medium and improving the nutritional value of live prey for essential amino acids and fatty acids. Tamaru et al. (1994) also suggested that the light intensity reduction linked to the concentration of phytoplankton may also improve the ability of the larvae to capture food.
N. oculata is the main species added to the larval tanks during the first 15 or 25 days at about 300.103 cells/ml (Gautier & Hussenot, 2005; Tamaru et al., 2005). Eda et al. (1990) and Lee and Kelley (1991) recommended 500.103–700.103 cells/ml. Moreover, Harel et al. (1998) reported that larvae did not survive beyond 14 days in the absence of phytoplankton and that survival in the presence of Isochrysis galbana was three times as high as compared with N. oculata.

Artificial feed can be provided from day 20–25 and weaning is complete around day 35 (Gautier and Hussenot, 2005; Tamaru et al., 2005). There is no formulated diet developed for flathead grey mullet juveniles but other fish feeds, ground into small particles were successfully used (Lee and Kelley, 1991). Harel et al. (1998) used a sea bream diet (200–400 µm) at 10 percent BW.

While shifting from a strictly carnivorous regime into a more omnivorous one, mullet fry naturally start feeding on benthic diatoms even on the sides of the tanks and nursery tanks are usually located outdoor (Tamaru et al., 2005). Mullet can then be fed with formulated feeds or plant origin feedstuff with relatively high protein contents such as rice bran or wheat flour (Gautier and Hussenot, 2005).

Better growth rate and survival were obtained in floating cages in fertilized ponds when feeding the fish twice daily instead of once (Essa, 1996).

The rate of digestion is slower at lower salinities than at higher salinities, and food intake is higher at the lower salinities (Perera and De Silva, 1978). Moreover, the time required to reach satiation by the fry decreases with the growth from 110–130 min. to 40 min. and to 10 min. at days 7–25, 33–40 and 56 respectively (Xu et al., 1985).

Polyunsaturated fatty acids such as EPA, DHA and arachidonic acid are important for good egg quality (Tamaru et al., 2005). They are essentially provided by the fish oil in the feed. The algae consumed by the fish within the pond are also a good source of arachidonic acid. In Hawai, broodstock are often fed with sinking channel catfish feed at 3 percent BW/day (Tamaru et al., 2005). Commercial trout feed with a CP content not less than 40 percent has been also used as a primary food source (Lee and Kelley, 1991).

There is no real production of commercial feeds specialized for flathead grey mullet. However, dry or moist farm-made feeds may be used (Table 6). Moreover, this species often produced in polyculture, can be fed from pellets left over in the pond by other species (Liao and Chao, 1991).

All the ingredients suitable for herbivorous species can be blend into the feed (Table 7) and cheap plant origin protein ingredients should be preferred to expensive ones such as fishmeal while performing least cost feed formulations.

A study from Kalla et al. (2003) has shown that growth rate, apparent protein digestibility and gross energy retention increased with increasing replacement of fishmeal by hydrothermically processed full fat soybean up to 75 g/kg diet. Protein, fat and energy contents of the carcass increased with the inclusion levels of processed soybean, and ammonia excretion and phosphate production within the rearing environment decreased accordingly.

Wassef et al. (2001) obtained the best weight gain and feed efficiency with fish fed 20 percent Ulva meal. They also reported good results with 40 percent dietary yeast enriched with vitamin E. Examples of feed formulae are presented in Table 9.

Vitamins and minerals should also be incorporated in the feed and examples of premixes compositions are given in Tables 11 and 12. Swart et al. (2001b) demonstrated that there was no direct benefit from using probiotics in term of growth and feed assimilation. Spermatogenesis can be induced and maintained by adding 17α-methyltestosterone to the diet at a rate of 12.5 mg/kg body weight (Weber and Lee, 1985). Commonly used growth hormones in formulated feed for mullet is given in Table 10.

M. cephalus cannot select organic matters too small and large particles increase the rate of feed eliminated. Feeds with particles between 100 and 250 µm lead to an efficient use of the proteins and generate fewer wastes (Ghion, 1986).