Aquaculture Feed and Fertilizer Resources Information System
 

Flathead grey mullet - Natural food and feeding habits

Natural food fluctuations (percent of total food intake) of flathead grey mullet (Mugil cephalus) are presented in Table 1.

Larvae
Flathead grey mullet larvae are carnivorous, visual and selective feeders, feeding on mosquito larvae, copepods and other zooplankton (Odum, 1970, Brusle, 1981).

The feeding behaviour gradually changes with the length. The main trend is a stronger dependence on benthic detritus and sediment. De Silva and Wijeyarantes, (1977) found that detritus and sand appeared in the gut when the fish reaches 25 mm TL (Total Length) and they concluded that this size represents a transition from planktonic to benthic feeding habit.

The ontogenetic shift in the diet is connected with metamorphic changes including elongation and convolution of the intestine, and changes in the morphology of the teeth and lips (Major, 1978).

Adults
The diet of adult flathead grey mullet consists of microalgae (epiphytic and benthic), plant detritus, inorganic sediment particles, and benthic animal to a lesser extent (Thomson, 1966; Odum, 1970). There is nevertheless a wide variability in the diet according to the season and the location. Juvenile can also feed on the “marine snow”, which often occurs in estuaries and near-shore waters (Larson and Shanks, 1996).

Thomson (1966) suggested that the ingested sediment particles function as a grinding substrate in the degradation of plant cell walls in a gizzard-like pyloric stomach.

Adults mainly feed on the bottom but also on surface water “scum” composed of accumulations of microalgae (Odum, 1970). They prefer fine particles with a diameter between 10 and 200 µm expelling the coarser material through a pharyngobranchial organ which acts as a mechanical and gustative filter (Brusle, 1981).

There are seasonal variations in the ingestion intensity, and in the food items composition and proportion in the gut. Empty digestive tracts may also be found during extreme weather conditions (Brusle, 1981).

M. cephalus feed diurnally, with maximum intensity occurring at about 11.00 hours and little or no feeding occurring at night (Collins, 1981). Odum (1970) also showed a tidal influence on the feeding behaviour. The retention time of food material ranges between 2 and 6 hours (Odum, 1970).