Food and Feeding Habit of Heterotis Niloticus in Oguta Lake, IMO State, Nigeria

The importance offish in the economy and ecology of inland water has generated a lot of interest. Over the years aquaculture has gained a rapid interest due to importance offish as a cheap source of animal protein, since beef is beyond the reach of an average Nigerian citizen these days (Akegbejo, 1995).

Fish like other animals required adequate nutrition to grow and survive in the wild, nature offers a great diversity of foods; these include: nutrients in solution and a host of different plants and animals. However in ponds, natural food is not sufficient to sustain the fish culture, especially in ponds with high density of fish.

For efficient and effective management in fish farming and in order to avoid high cost of producing fish, there is need for proper and adequate nutrition strategies, which can only be achieved via proper understanding of the food and feeding habit of the fish to be cultured. Heterotis niloticus (Cuvier, 1829) of the family Arapaimidae, is widely distributed in Nigeria, most especially in the fresh waters of Nigeria rivers. There is only one species of this genus Heterotis, hence species niloticus (Akegbejo-Samason, 1995). It constitutes an important food source within the region and comprises a portion of the inland fishes in Nigerian due to its delicacy, as it is widely known, but not popularly used in research and production probably due to its inability to easily adapt to environment changes. Heterotis niloticus grow reasonable fast from one to eleven months during culture.

Most Rivers and lakes in Nigeria, contain commercially culturable species offish but very little information is valuable on food and feeding habits Heterotis niloticus, in Oguta lake. It is in this view that a study on the food and feeding habits of Heterotis niloticus was carried out in Oguta lake of Imo State.

Heterotis niloticus is a pelagic species, it occurs in shallow waters where it feeds on invertebrates, copepods and chironomids (Hickley and Bailey, 1987). Young ones are found in swampy places among aquatic vegetation (Moreau 1982, Dankwa et al.,1999), adults live in the open water of rivers and lakes, where they can be found in the pelagic zone as well as the littoral zone (Moreau 1982). Its auxiliary branchial air breathing organs enable it to survive in deoxygenated water; the hardiness of this fish, together with its great growth rate, make it a candidate for aquaculture in Africa and it has been transported to a number of countires for this purpose (Bake and Sadiku, 2005). Escapees from ponds into the wilds resulted in established populations which form the basis for Fisheries and Aquaculture. (Akintunde, 1977).

This species is considered as a mud feeder (Hickley and Bailey 1987), but in West Africa it is also seen as a phytoplankton feeder. It feeds mostly on plankton, being the only plankton feeder of the Osteoguosssidae (Dankwe et al., 1999). It has a superabranarial organ which has a sensory function. During breeding, it creates a circular nest in swamps. The young’sleave the nest after a few days and are guarded by the male (Balon, 1975). Heterotis niloticus breeds in the wet season in swamps and flood plains. It builds a circular nest about one millimeter (1mm), in diameter and 20 to 60m deep (Bailey).

The rim of the nest in a high wallis formed out of plank winks, about 15-20cm thick and projecting. Above the water surface, the bottom is a clean platform of clay or mud (Balon, 1975). After the spawning act, the fish leave the way of a hole in wall, through which 5 days later, the young leave the nest and are guarded by the male. The youngs posses external gills for breathing.

Heterotis niloticus is a long-bodied fish with large scales, long dorsal and anal fins set far back on the body and a rounded caudal fin it height is 3.5 to 5 times standard length (SL). It has been reported to reach up to 1m (3.3ft) SLand weight up to 10.2kg (22Ib).

This fish is gray, brown or bronze in colour. Colouration is uniform in adults, but juveniles often have air-breathing organs or less-bronchia, enabling them to survive in oxygen depleted water. A suprachiiae organ allows it to concentrate on small planktonic and food particles and also has a sensory function.