OPIS Foundation

A. Artificial Propagation and Fingerling production

Fingerling production will be the responsibility of the Foundation hatchery and processing facility. Our company will be responsible for a reliable supply of fingerlings for our partnering fish farms who will then be responsible for the out growth phase of raising the fish to a marketable size. 

Artificial propagation through hormone treatment, artificial fertilization and incubation of fertilized eggs, and subsequent rearing up to fingerling size has several advantages:

• better rates of fertilization and hatching;
• protection against enemies and unfavorable environmental conditions;
• better conditions for growth and survival.

Broodstock and hatchery management

(A) Hatchery (pond nursing) - Layout of a catfish hatchery where the fry are nursed in earthen ponds.                                                                               

 

(B) Hatchery (hatchery nursing) - Layout of a catfish hatchery where the fry are nursed in the hatchery

Scale 1cm to 1m 

 

Breeders can be collected either from nature or from fish ponds. The capture of wild broodfish is recommended during: (i) the breeding season when mature catfish aggregate in or towards the shallow spawning grounds or (ii) the dry season when they are relatively concentrated in their reduced natural habitats, especially small pools and streams.

An alternative to capturing broodfish from spawning grounds or natural habitats is the rearing of fingerlings up to maturity in fish ponds. At harvest, breeders are selected and transferred to the holding unit in the hatchery, or to a special broodfish pond.

Hatchery management is simplified if only two age-groups are kept in the hatchery, i.e., broodfish and one batch of juveniles up to 1g at a time. One gram fingerlings are the minimum size required for proper stocking of on-growing ponds. Broodstock maintained for at least one year under controlled conditions in a hatchery lose their seasonal reproductive cycle and mature breeders become available year round. Consequently two stocks of broodfish should be maintained in the hatchery, i.e., (i) actual broodstock for propagation and (ii) conditioning broodstock.

Individual broodfish of weight 0.5-1 kg are preferable. They have a substantial quantity of mature eggs and are easy to manipulate.

The hatchery will seek an annual production capacity of 1.25 billion fingerlings. This will require a total incubation capacity of 2,000 kg of fertilized eggs/batch. This amount of eggs can be produced by about 40,000 females of 500 grams each and be incubated in 10,000 incubation troughs.

The period of indoor rearing of fry up to early fingerlings of about 1 gram varies from six to eight weeks, depending on water temperature and feed quality. This would mean that artificial propagation should be carried out every six to eight weeks and dividing the females into two broods to ensure a constant supply. If nursing is in ponds, artificial breeding should be carried out once or twice every month in order to meet the annual production target of 1.25 billion fingerlings.

The same female broodfish can be induced to reproduce artificially every four to six weeks without affecting either the quality or quantity of eggs obtained after stripping.

The size of the male broodstock depends on the number of males required for each of the artificial propagations and the number of artificial reproductions per year. One, and in rare cases two, males need to be dissected for the procurement of milt.

Taking into account the above and with a large safety margin, the following stock of broodfish should be maintained in separate tanks in the hatchery:

• 250,000 males as broodstock for propagation
• 250,000 females as broodstock for propagation
• 250,000 males for conditioning
• 250,000 females for conditioning.

A reserve broodstock of about 375,000 males and 375,000 females should be maintained in one pond for safety reasons. In ponds, two sexes can be maintained together because they do not spawn in confined waters.

Qualitatively and quantitatively adequate sexual products are prerequisites for artificial propagation. Therefore, sexually mature and healthy breeders kept under suitable environmental conditions and with an adequate food supply are mandatory. Optimal hatchery management including the following factors is required to maintain broodfish under these optimal breeding conditions.

The breeders are kept in rectangular tanks of about 1 to 1.5 m³. The water inflow is at one end, while the water flows out at the other end through a turn-down pipe. Each tank may be stocked with 100-150 kg fish/m³. Oxygen concentration in the water should not fall below 3 mg/l. Approximate water flow rates and turnover times are given in the Table below:

It is of foremost importance that the preparation of the nursing ponds is synchronized with the artificial propagation, to ensure that both the fry and the nursery ponds are "ready" at the desired moment. 

SCHEDULE FOR SYNCHRONIZED ARTIFICIAL PROPOGATION
AND POND NURSING ACTIVITIES

Day	Artificial propagation	Nursing pond
- 4	Injection of broodfish	-
- 3	Stripping and incubation	Cleaning ponds: cutting grass, removal of silt, etc.
- 2	Hatching, separation of normal larvae and spoiled eggs	Liming
- 1	Cleaning larval troughs	Water filling and fertilization
0	-	Stocking of fry
+ 3, 7, 10 14, 17, 21	-	Fertilization
+ 26-30	-	Harvest

 

Once the fry are stocked, a high standing crop of zooplankton must be maintained in the nursery ponds by regular fertilization to ensure good growth and high survival. The following fertilization may be applied twice weekly: 5 kg manure, 0.1 kg nitrogen and 0.025 kg phosphorus per 100 m² of pond.

Feeding is not necessary during the first week of nursing since the early fry do not accept artificial feedstuffs. However, after one week the catfish need to be fed with a finely ground and sieved (through 0.25-0.5 mm mesh), artificial feed. This feed can be composed of blood meal or fish meal (25%), brewers' yeast (25%), oil cakes (heated soy/groundnut/cotton/sesame cake, 25%) and wheat or rice bran (25%). Feeds are distributed twice a day at a rate (per 100 m²) of 0.5 kg during the second week after stocking, 0.75 kg during the third week, and 1 kg during the fourth week. After a week of feeding, the size of the feed particles should be increased to 0.5-1 mm but the food composition remains the same.

After about one month, the fingerlings (weighing 2-5 grams) are harvested from the nursing pond. The fingerlings are collected in a concrete or wooden harvest boxes fixed to the outlet pipe. After harvest, the fingerlings are sold immediately or stocked temporarily in small storage ponds up to a density of 100-200/m².

Sorting of the fingerlings by size is advisable in order to supply homogeneous size fingerlings to the fish farmers. The different size classes can be temporarily stored in hapas placed in a pond or concrete tank.

B. Out Growing (production) Phase

At end of one month, fingerlings will be available for our partnering fish farms, who will raise them to maturity over the next six months in production ponds.

Generally, catfish ponds are constructed in the same way as ponds for other fish species. Specific details on catfish culture given here are based on the results of the Dutch Cooperation/FAO project in Central African Republic and those of local fish farmers in that country supported by the extension service of this project..

Up to the present time, very little information is available on ponds larger than 0.1 hectare as ponds of this size are scarce in Africa, particularly among private fish farmers. Hence, the recommended size of on-growing ponds is 400 to 1,000 m².  Rectangular ponds are most suitable for seining. The average water depth should be about 1 m.  Shallower ponds should be avoided, as the water temperature in such ponds may become too high and they may easily be invaded by aquatic plants. The water supply should be about 10 l/s/ha with a minimum of 5 l/s/ha.

Intensive monoculture of catfish

The intensive monoculture of catfish aims at optimum production and optimum profit. High yields may be obtained since catfish can be stocked at relatively high densities due to its accessory air breathing organ. At these high densities, the natural food production of the pond cannot meet the food requirements. External food supply with a balanced complete feed becomes a necessity.

The specific prerequisites for intensive monoculture of catfish, based on high stocking densities and artificial feeding with a balanced diet, are:

• i. availability of suitable food sources to produce balanced diets,
• ii. essential investment funds for operating costs
• iii. availability of a competent farm manager.

Preparation of ponds. Pond preparation will be the responsibility of the Foundation. Ponds will be a standard 2 water acres with farms averaging about 12 ponds each.

Stocking. The stocking rate, depending on the marketable size desired, and may vary from 2 to 10 fingerlings/m², which corresponds to a marketable size of about 500 and 200 grams respectively after six months. The highest yield will be obtained with the highest stocking density.

Feeding. A balanced compounded diet is a prerequisite for intensive catfish monoculture. The table below shows that the catfish should be fed with a diet containing 30-35% digestible protein (40-50% crude protein) and 2,500-3,500 calories digestible energy/kg food (3 500-4 500 calories crude energy/kg food).

Growth rate increases with increasing protein levels at a fixed energy level and vice versa. Therefore, the recommended values indicated in the table below are those which have given acceptable growth rates and which can be reasonably obtained using local sources of feed ingredients.

RECOMMENDED NUTRIENT LEVELS FOR INTENSIVE
CLARIAS GARIEPINUS FARMING
(in % dry matter)

Nutrient	Fry and fingerlings	Growers	Broodfish
Digestible protein	35-40	30-35	35-40
Digestible energy (kcal/g)	3-4	2.5-3.5	3-4
Ca (min-max)	0.8-1.5	0.5-1.8	0.8-1.5
P, available (min-max)	0.6-1	0.5-1	0.6-1
Methionine + Cystine (min)	1.2	0.9	1
Lysine (min)	2	1.6	1.8

The recommended feeding rates between 21° and 33°C, corresponding with maximum growth rates and optimum food conversion, have been determined by Hogendoorn et al. (1983). These feeding rates are based on laboratory results where fish were fed with a commercial trout diet (crude protein 50%; gross energy 5,200 cal/kg food). In practice, it has been found that slightly higher feeding rates may be applied during the first month(s) of culture in order to acclimatize the fish to the feed and the feeding place, while lower feeding levels should be applied during the last two to three months due to deteriorating water quality in static ponds.

In practice, the amount of feed to be distributed is calculated for a period of two weeks and adjusted every four to six weeks after estimating the average body weight. A fish sample should be taken using a cast or seine net for this purpose. The biomass of the catfish and the daily amount of feed are calculated according to the recorded average body weight and estimated survival rate.

It is difficult to predict growth rates and survival as they depend on many factors such as density, feed quality, temperature, pond fertility, and management, which are site and operator specific. However, estimates of biological data including average body weight, survival and standing crop as well as the daily amount of feed for a typical catfish culture system (stocking density 10/m²; temperature 25°-27°C), are given in the table on the following page as an example.

Equal rations of feed are distributed three times a day, e.g., at 07.00 h, 12.00 h and 17.00 h, from one fixed place in the pond. They are distributed over a surface area of about 2 × 2 m in order to reduce feed competition to a minimum. There are no direct indications that the fish effectively ingest the pellets, since pellets generally sink to the bottom. A high concentration of air bubbles is the only indirect sign that food intake occurs. About 30-60 minutes after feeding, when air bubbles are no longer observed, the pond bottom may be checked with a fine mesh dip net for remaining feed. If there is no feed left and if the water quality is good, the feeding rate may be increased. If there is excessive feed left, the feeding rate should be decreased the next time. 

ESTIMATES OF BIOLOGICAL PARAMETERS
FOR A TYPICAL CATFISH MONOCULTURE
(density 10/m²; mean temperature 25°-27°C)

Week	Mean body weight (g)	Survival (%)	Biomass (kg/100 m2)	Feeding rate (% body weight/day)	Feed ration (g/100 m2/day)
0	1	100	1.0	10.0	100
2	5	70	3.5	7.5	250
4	10	65	6.5	4.5	300
6	18	60	10.8	4.0	400
8	27	60	10.2	3.3	525
10	36	60	21.6	3.0	650
12	52	55	28.6	2.7	775
14	65	55	35.7	2.6	900
16	79	55	43.4	2.4	1 025
18	102	50	51.0	2.3	1 150
20	130	50	65.0	2.1	1 350
22	160	50	80.0	1.9	4 500
24	200	50	100.0	1.8	harvest

 

Harvesting: After about six months, when catfish have reached the desired marketable size (200-250 grams at a stocking rate of 10/m²), the whole crop should be harvested.

As stated earlier, production is site and operator specific. However, under adequate management conditions, a net production of 160-240 kg/are/year (16-24 t/ha/year), and a food conversion rate between 1.5 and 2.5 may be obtained. The rather wide divergence in expected production is caused mainly by the difference in survival, which is above all management specific. At a stocking rate of 10/m², survival ranging from 50 to 75% can be expected. There is a substantial decrease of survival rate with increasing stocking rate. For example, at 20/m², survival may be as low as 40%, while at 2/m² this may be as high as 90%.