ABSTRACT
Grey mullets have often been described as mud-eaters, iliophagous, detritus feeders, deposit feeders and interface feeders (Brusle 1981) because the diet of most of these species is based on the organic matter present in the sediment, although they can also exploit benthic invertebrates, green fi lamentous macroalgae, plankton and other suspended organic matter. No other group of fi sh relies so much on microphytobenthos, which represents a major component of the diet of most grey mullet species. Most marine herbivorous fi shes consume primarily fl eshy macroalgae and seagrasses (parrot fi shes, sea breams and surgeon fi shes), turf algae (damselfi shes) or encrusting coralline algae (some parrot fi shes), but not the microscopic algae growing on the sediment. Some freshwater cyprinids and armoured catfi shes also consume signifi cant amounts of detritus and benthic fi lamentous and microscopic benthic algae, but scrape them from rocks and boulders instead of fi ltering from the water column and the sediment. Only the Indo-Pacifi c milkfi sh Chanos chanos and some tilapias, native to African freshwater and estuarine ecosystems, have diets close to those of grey mullets and share with them the ability to behave alternatively as deposit feeders and suspension feeders (Odum 1970, Whitfi eld and Blaber 1978). All these species are relatively large and forage primarily on microscopic algae, thus bypassing steps in the food web and telescoping primary production to fi sheries yield (Hiatt 1944, Odum 1970).
