8.1.1. Economics of fingerling production
8.1.2. Economics of polyculture and monoculture
Limited information is available concerning the economics of catfish rearing in Africa due to the fact that most of the work carried out to date has been oriented toward the technical development and implementation of fish rearing techniques. However, some economic information as obtained by the authors from large research stations in the Republic of the Congo (13 ha) and in the Central African Republic (3.5 ha) are presented.
In the Republic of the Congo the farm cost for the production of fingerlings in protected nursery ponds was US$ 0.07/fingerling. By contrast, the production costs for an indoor hatchery in the Central African Republic, using Artemia salina nauplii and formulated feed were US$ 0.14/fingerling. Table 15 presents an economic comparison of the two different fingerling production systems.
Table 15. Division of costs (expressed as % of the total costs) of two African catfish production systems: pond rearing and hatchery rearing using Artemia salina nauplii and formulated feeds.
|
Pond rearing |
Indoor hatchery rearing |
Labour |
68.0 |
16.2 |
Operating costs |
25.9 |
27.6 |
Depreciation of investments (15 years) |
6.1 |
56.2 |
13 1990 price level, the Republic of the CongoTable 16. Economics of a pond based hatchery for Clarias gariepinus
14 ERR is calculated over a 30-year period
Production parameters |
||
Production |
35 fingerlings/m2 |
|
No. of rearing cycles |
8 cycles/year |
|
Average weight/fingerling |
3 g |
|
Pond size |
200 m2 |
|
Total pond area |
1 000 m2 |
|
Total fingerling production |
280 000 fingerlings/year |
|
Food conversion rice bran |
7 |
|
|
||
Inputs |
||
Rice bran |
5 880 kg/year |
|
Broodstock feed |
800 kg/year |
|
Labour |
30 person-months |
|
Material |
1 000 US$/year |
|
Sundry |
200 US$/year |
|
Operation & Maintenance |
10% |
|
|
||
Prices |
||
Rice bran |
0,25 US$/kg |
|
Brood stock feed |
0,8 US$/kg |
|
Fingerlings |
0,1 US$/piece |
|
Labour |
450 US$/month |
|
|
||
Investments |
|
Percentage of Investments |
5 ponds, 200 m2 each |
6000 US$ |
50% |
1 broodstock pond, 200 m2 |
900 US$ |
8% |
Building with basins |
3000 US$ |
25% |
Store |
2000 US$ |
17% |
TOTAL |
11 900 US$ |
100% |
|
||
Farmcost/000 piece |
|
Percentage of Costs |
Feed |
7,5 US$/000 piece |
11% |
Labour |
48,2 US$/000 piece |
73% |
Material |
3,6 US$/000 piece |
5% |
Sundry |
0,7 US$/000 piece |
1% |
O&M |
6,0 US$/000 piece |
9% |
TOTAL |
66,0 US$/000 piece |
100% |
|
||
Investments/000 piece |
|
|
Rearing ponds |
21,4 US$/000 piece |
|
Broodstock pond |
3,2 US$/000 piece |
|
Building |
10,7 US$/000 piece |
|
Store |
7,1 US$/000 piece |
|
TOTAL |
42,5 US$/000 piece |
|
This chapter presents preliminary information on the economic performance of polyculture and monoculture operations with African catfish. However, it should be mentioned at this point that the analysis is made on the basis of biological data compiled for monoculture operations in the Central African Republic (1984-1985), and biological data compiled for polyculture operations in the Republic of the Congo (1986-1990) using prices from the Republic of the Congo (1990, US$ 1 = FCFA 285). The main economic parameters are summarized in Table 17 and details are given in Tables 18 and 19.
Table 17. Economic parameters of monoculture of C. gariepinus and polyculture of C. gariepinus with O. niloticus.
Parameters |
Monoculture |
Polyculture |
Production |
10 000 |
6 500 |
Investments |
180 000 |
180 000 |
Farm costs |
114 000 |
36 000 |
ERR (%) |
35 |
56 |
Net Cashflow |
118 000 |
120 000 |
TABLE 18: ECONOMICS OF MONOCULTURE OF CLARIAS GARIEPINUS
Production parameters |
|
|
Production level |
100 kg/100 m2 |
|
No. of rearing cycles |
1,8 Cycles/year |
|
Stocking density |
10 fingerlings/m2 |
|
Pond size |
400 m2 |
|
Food conversion composed feed |
3 |
|
Total annual production |
720 kg |
|
|
|
|
Inputs |
|
|
Fingerlings |
7200 No./year |
|
Composed feed |
2160 kg/year |
|
Fertilizers |
270 kg/year |
|
Labour |
80 person-days/year |
|
Sundry |
20000 FCFA/year |
|
Operation & Maintenance |
10% |
|
|
|
|
Prices |
|
|
Composed feed |
140 FCFA/kg |
|
Fertilizers |
80 FCFA/kg |
|
Catfish fingerlings |
10 FCFA/piece |
|
Labour |
1000 FCFA/dav |
|
C. gariepinus (200 g) |
800 FCFA/kg |
|
|
|
|
Investments |
|
|
1 pond (400 m2) |
150000 FCFA |
|
Equipment |
30000 FCFA |
|
TOTAL |
180000 FCFA |
|
|
|
|
Farmcost/100 m2 |
|
Percentage of costs |
Feed |
75600 FCFA/100 m2 |
66% |
Fertilizers |
5400 FCFA/100 m2 |
5% |
Fingerlings |
18000 FCFA/100 m2 |
16% |
Sundry |
5000 FCFA/100 m2 |
4% |
O&M |
10400 FCFA/100 m2 |
9% |
TOTAL |
114.400 FCFA/100 m2 |
100% |
|
|
|
Investments/100 m2 |
|
Percentage of investments |
Pond |
37500 FCFA/100 m2 |
83% |
Equipment |
7500 FCFA/100 m2 |
17% |
TOTAL |
45 000 FCFA/100 m2 |
100% |
Production parameters |
|
|
Production level |
65kg/100 m2 |
|
No. of rearing cycles |
1,8 Cycles/year |
|
Stocking density O. Niloticus |
2,2 fingerlings/m2 |
|
Stocking density C. Gariepinus |
0-8 fingerlings/m2 |
|
Pond size |
400 m2 |
|
Food conversion rice bran |
7 |
|
Total annual production |
468kg |
|
Percentage male tilapia at harvest |
65% |
304 kg/year |
Percentage female tilapia at harvest |
15% |
70 kg/year |
Percentage tilapia fingerlings at harvest |
3% |
14 kg/year |
Percentage catfish at harvest |
17% |
80 kg/year |
|
|
|
Inputs |
|
|
Tilapia fingerlings |
1584 No./year |
|
Catfish fingerlings |
576 No./year |
|
Feed |
3276 kg/year |
|
Labour |
80 person-days/year |
|
Sundry |
20000 FCFA/year |
|
Operation & Maintenance |
10% |
|
|
|
|
Prices |
|
|
Rice bran |
30 FCFA/kg |
|
Tilapia fingerling |
6 FCFA/piece |
|
Catfish fingerlings |
10 FCFA/piece |
|
Labour |
1000 FCFA/day |
|
Male Tilapia (200 g) |
600 FCFA/kg |
|
Female Tilapia (100 g) |
250 FCFA/kg |
|
African Catfish (200 g) |
800 FCFA/kg |
|
|
|
|
Investments |
|
|
1 pond (400 m2) |
150000 FCFA |
|
Equipment |
30000 FCFA |
|
TOTAL |
180000 FCFA |
|
|
|
|
Farmcost/100 m2 |
|
Percentage of costs |
Rice bran |
24570 FCFA/100 m2 |
67% |
Tilapia fingerlings |
2376 FCFA/100 m2 |
6% |
African catfish fingerlings |
1440 FCFA/100 m2 |
4% |
Sundry |
5000 FCFA/100 m2 |
14% |
O&M |
3339 FCFA/100 m2 |
9% |
TOTAL |
36.725 FCFA/100 m2 |
100% |
|
|
|
Investments/100 m2 |
|
Percentage of investments |
Pond |
37500 FCFA/100 m2 |
83% |
Equipment |
7500 FCFA/100 m2 |
17% |
TOTAL |
45000 FCFA/100 m2 |
100% |
In general, diseases have not been found to be a serious problem within polyculture or monoculture operations of African catfish at low stocking densities (up to 5 fish/m2). Although some fungal, parasitic and bacterial diseases can occur these will not be described here, as this has been well described in several handbooks (Amlacher, 1970 and Reichenbach-Klinke and Elkan, 1965). However, more disease problems will be encountered at higher stocking densities (over 10/m2, the Thai rearing system), as the pond environment often quickly deteriorates. The specific disease problems encountered at high stocking densities have been well described in two handbooks produced in Thailand (Anonymous, 1981, Tonguthai et al., 1993). However, three diseases all encountered in intensive rearing systems and indoor hatcheries in Africa are described below.
Crack head disease is a catfish disease which has been reported from intensive pond rearing systems and hatcheries in Africa (de Graaf, 1989, Janssen, 1985c). Although the cause of this disease is still not fully understood, adverse water quality due to overfeeding and Vitamin C deficiency are believed to be the main factors causing crack head disease. The reported clinical symptoms have included: slightly distended abdomen due to septicaemia haemorrhage, and occasionally exophthalmia (pop-eye). This disease can be detected at an early stage, with affected fish showing a reddish lateral line on the skull, between the two air chambers, parallel to the skull plate joints. In the final stage the skull will break laterally followed by death. As soon as the external symptoms of the disease (reddish lateral line) are observed during sampling, feeding should be significantly reduced, additional vitamin C (ascorbic acid) added to the feed mixture and the pond water replaced. Generally, fish usually recover after a few weeks, after which feeding can be increased steadily little by little.
Infections by myxobacteria was found to be a major problem in a hatchery in the Central African Republic and caused heavy mortalities in a matter of several days. The major cause is bad or poor management, the fish being damaged by handling, water quality deterioration, and increased fish stress. The reported clinical symptoms include: fish remain in a vertical position or exhibit a waddling swimming behaviour, with white spots appearing on the skin, especially on the fins. However, proper hatchery management reduces the risk of myxobacteria and infected fish can be treated with a Furazolidone-bath at a dose of 50 ppm for one hour.
In addition, during the yolk-sac stage, larvae sometimes develop oedema (body swelling) ventral from the cardiac cavity which can result in heavy mortalities (up to 90%). The major cause is believed to be due to the horizontal transmission (from female broodstock) of an Aeromonas bacteria. Infected larvae can be treated with a bath of Oxytetracycline at a dose of 50 ppm. Moreoever, Oedema in yolk-sac hatchlings can be prevented by only using healthy broodstock. For example, in the Republic of the Congo where broodstock were kept in ponds, the disease never occurred, while in Ivory Coast, where the broodstock were kept indoors, there were clinical signs of crackhead disease, and oedema in the yolk sac larvae was endemic (de Graaf, 1989).
Another catfish species which has been cultivated in Africa is Heterobranchus longifilus. By contrast, in South-East Asia other catfish species are cultivated such as Clarias macrocephalus, C. batrachus, and Pangassius sutshi. In the early eighties C. gariepinus was introduced into South-East Asia and its culture has since then spread rapidly due to its higher growth rate compared with the local catfish species. However, the introduction was not a complete success as several socio-economic factors were neglected. For example, in Viet Nam consumers refused to buy C. gariepinus at a reasonable price because of its taste and relatively large head (which cannot be consumed).
Interspecific cross-breeding in fish may lead to hybrids with valuable characteristics for culture (sterility, monosex populations, heterosis for disease resistance or growth rate, etc.).
Hybridization among the Asiatic clarids have involved C. macrocephalus and C. Batrachus (Boonbrahm et al., 1977), C. batrachus or C. macrocephalus × Pangasius sutshi (Tarnchalanukit, 1986), and C. batrachus x Heteropneustes fossilis (Mukhopadathy and Dehadrai, 1987). Moreoever, in June 1988 staff from the Department of Fisheries in Thailand succeeded in artificially crossbreeding the female C. macrocephalus with male C. gariepinus. This hybrid reportedly grows faster and has more resistance to diseases than other hybrids and the hybrid is now rapidly replacing C. macrocephalus and C. batrachus in the Thai fish markets (Tonguthai et al., 1993). This hybrid has also became very popular in Viet Nam, and in Bangladesh a hybrid between P. sutshi and C. gariepinus has recently been introduced on the market (de Graaf, unpublished data).
In Africa, hybridization trials between C. gariepinus and Heterobranchus fossilis have been carried out (Hecht and Lublinkhof, 1985 and Legendre et al., 1992). Legendre et al. (1992) found that the reciprocal hybrids were viable; their survival rates being similar to those found in the maternal species. Furthermore, the growth rate of H. fossilis and their hybrids have been found to be higher than that of C. gariepinus. However, in the reciprocal hybrids, the sexual maturity of the female was only attained after 20-21 months, which is much later than for C. gariepinus (5-7 months) or for H. fossilis (12-14 months).
However, these male and female hybrids are not sterile, and viable fry can be obtained from F2 or backcross fertilization. Despite the eventual advantages from a production point of view it is the opinion of the authors that this hybrid should not be produced as the environmental risks are too high; escaping hybrids could contaminate natural fish stocks.