INTRODUCTION

Catfishes of the family Claridae comprise the most commonly cultivated fishes in Nigeria. The growth of aquaculture in Nigeria now is largely being boosted by a steady rise in catfish culture. Since the culture of Clarias gariepinus through hypophysation was initiated in Western Nigeria in 1973, the procedure has been widely practiced throughout Nigeria thus leading to increase of farm-raised catfishes from the 80’s to date. The favoured catfish species in Nigeria aquaculture include: Clarias gariepinus, Heterobranchus bidorsalis, Clarias X Heterobranchus hybrid (Heteroclarias)and Clarias nigrodigitatus.Heterobranchus sp is the more commonly cultured fish in the South Eastern parts of Nigeria.

LARVAL PRODUCTION

Despite the popularity of the African catfish and its great market potentials, the production is still basically at subsistence level  due majorly to inadequate availability of seed for stocking and feed problems. In Europe, about 75% of Clarias fingerling demands are supplied by a few producers. In Nigeria however, the fingerlings supplied from both the government and privately owned hatcheries are not enough to meet the catfish farmers’ fingerling demands.

 Artificial propagation of C. gariepinus is now carried out in hatcheries with hormonal induction. Farmers have found the homoplastic pituitary gland suspension cheaper, practical and more highly reliable than the imported synthetic hormonal analogues. The C. gariepinus broodstock weight used for artificial breeding ranges between 0.3kg and 2kg (Olaleye, 2005). Despite the breakthrough with use of hormone in induced spawning; fry survival is still beset with a number of biotic and abiotic factors. The biotic factors include cannibalism, heavy predation by frogs/aquatic insects and the abiotic factors include water temperature, dissolved oxygen (>4.5mg/L-1), levels of ammonia. During the first week after stocking, the most critical factor for the successful nursing of the catfish larvae is the availability of zooplankton. Feeds and feeding of the larvae, fry and fingerlings of the catfishes have been most studied and shown to influence the growth and survival of the fish. Studies have revealed that live zooplankton is the preferred larval food. Many smallholdings merely rear larvae to fingerling size in organically fertilized ponds at a density of between 30-1000 larvae/m2 (Olaleye, 2005). Fingerlings are stocked into rearing ponds at a rate of 50-75 fish/m3 under good management.

THE CULTURE SYSTEM

Because of the cannibalistic nature of Clarias gariepinus, multiple sorting is essential. For outdoor fry/fingerlings rearing, screening of the tanks with mosquito nets is recommended to prevent dragonfly and other predatory insects from breeding in the ponds. Poly-culture of Clarias gariepinus and Tilapia species is practiced. A poly-culture of Clarias gariepinus and Oreochromis niloticus, integrated with poultry with some supplementary feeding had been shown to be viable.

FEED AND FEEDING

Feed and feeding of catfishes in grow outs ponds are perhaps the most documented in literature. Various efforts have been made to establish the crude protein and amino acid requirement of C. gariepinus. Ayinla (1988) recommended 35% and 40% crude protein (Cp) for raising table size and brood stock respectively. Of the 10 essential amino acids (EAA) required by warm water fish species, only 3 EAAs studied have been documented and these are arginnie, methionine and lysine. In order to formulate and compound aqua feeds that will meet the nutrient requirements of the catfish at affordable cost, several conventional and non-conventional animal by-products and plant residues have been tested to substitute or replace fishmeal (Table 1). Feeding development has moved from the use of single ingredient, broadcasting un-pelleted meal to pelleting and in fact the use of pelleted floating feed which has made a big difference to aquaculture development in Nigeria as C. gariepinus is being raised to maturity within 6 months.

HYBRIDIZATION OF Clarias gariepinus x Heterobranchus longifilis

The yearnings of farmers and scientists to have a farmed catfish that combines the fast growth traits of Heterobranchus spp and early maturing traits of C. gariepinus led to the development of a hybrid ‘Heteroclarias’ spp. The technology was widely accepted as it gave 58% internal rate of return (IRR) on investment (Adeogun et al, 1999).

CULTURE SYSTEM MODIFICATION

In the review of Oresegun et al (2007), it was stated that early fish farmers in Nigeria raised their fish in burrow pits, abandoned minefields and in earthen ponds on extensive production system. The introduction of concrete tanks allows for manageable pond size and modification of the environment through a water flow-through system and supplementary feeding thus allowing for higher fish yield. The advent of the indoor water re-circulatory system (WRS) has ushered in a new prospect for aquaculture. The introduction of WRS has created a turning point in the production of catfish in Nigeria. 

PROSPECTS AND PROBLEMS OF CULTURE

The story of aquaculture in Nigeria is essentially the story of catfish culture and the hope of fish supply in Nigeria hangs on its development and culture. Recent trends all over the world, point to a decline in landing from capture fisheries, an indicator that fish stocks have approached or even exceeded the point of maximum sustainable yield. Aquaculture therefore remains the only viable alternative for increasing fish production in order to meet the protein need of the people. It was observed that of the over 30,000MT of various freshwater and brackish water fish species caught in the year 2000, catfishes were more abundant next to Tilapines (Table 2). FAO (1993) reported that 27,488MT of catfishes produced in 1990 were consumed locally. This implies that there is still great need for higher production for both local and international markets.

Table 1: Some Plant Residues Used for Clariidae Culture in Nigeria.


Conventional Plant feedstuffs

Availability

    Fish species

              References


Groundnut cake

Adequate

C. anguillaris

Solomon et al. (1996); Eyo & Adelowo (1990)


Soybean cake;

Full fat/defatted;

Dehulled solvent extracted; Soybean flour;

Extruded/non extruded

Adequate

C. anguillaris

C. gariepinus

C. gariepinus

H. longifilis

Solomon et al. (1996); Balogun & Ologhobo (1989); Fashakin & Balogun (1996); Adewumi (2005)

Eyo et al. (2001); Fagbenro & Davis (2003)


Non-Conventional Plant feedstuffs

Availability

   Fish species

             References


Cocoa pod husk

Sesame seed

Adequate

N/A

C. isheriensiss

C. gariepinus

Fagbenro (1992)

Olukunle & Falaye (1998)


Table 2: Aquaculture Production in Nigeria


Species                                                                                                                               Tonnes


Tilapias, (Oreochromis niloticus), O. niloticus x O. Aureus hybrid)                                    11,363


Sarotherodon galilaeus, S. melanopleura, T. zilli, T. guinensis                                           3,025        

Mud catfishes (Clarias gariepinus, C. anguillaris, C.isheriensis)                                         6,553

Heterobranchus bidorsalis, H. longifilis, Heterobranchus x Clarias Hybrids                        2,832                                                           

Brackish water catfish (Chrysicthys nigrodigitatus)                                                             1,515

Carp (Common carp, Cyprinus carpio, Indian carps; goldfish Carrasus sp.)                      1,280                                                                                     

Heterotis (Heterotis niloticus)                                                                                                 654

Mullets (Mugil cephalus, Liza falcipinnis)                                                                               336

Snakehead (Parachanna obscrura)                                                                                       297

Other fishes                                                                                                                         2,921


Total                                                                                                                                  30,776


Fagbenro, et al. (2003)

A number of problems confront the production of catfish. Prominent among these are: poor management skills, scarcity of good quality seed, lack of capital, high cost of feed, faulty data collection, lack of environmental impact consideration and marketing of products.  Many people who are currently engaged in catfish farming lack management skill. Although there has been a lot of research work on the production of catfish feed and feeding, the use of cheap feedstuffs to replace or substitute fishmeal catfish farmers still rely on the costly, mostly imported pelleted floating feed.

The success of the industries for channel catfish, rainbow trout and the salmonids in the USA is due mainly to the availability of pelleted diets formulated based on the results obtained from the nutritional studies of fishes over many years. There is urgent need for co-ordination of such research work and the feed manufacturers’ access to the relevant data for quality and relatively cheap feed production.

The Federal/State governments’ public/private partnership initiative programmes and the various private concerns establishing standard hatcheries are gradually yielding results to solve the problem of seed scarcity. However, to produce good quality seed, aquaculture needs to explore the potential of genetics. As at today, most teaching institutions do not have well equipped genetic laboratories where research can be carried out on the production of genetically improved catfish species (Omitoyin, 2007).

CONCLUSION

Considerable effort had been devoted to the study and production of Clarias and Heterobranchuis spp in Nigeria. Catfish farming has continued to attract private sector initiative compared to earlier public or government-sponsored programmes. If the associated problems of production, especially the twin issue of feed production and fingerling supply are tackled, Nigeria will soon become a world exporter of catfish. 

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