Production of Pulchellus Carp

The pulchellus carp has been described with various names like Puntius pulchellus, Puntius dobsoni and Hypselobarbus pulchellus due to the wide colour variations seen not only in juvenile but also in maturing male and female of the species. This endemic fish seen in the peninsular rivers is presently included in the list of critically endangered species. It is a bentho-pelagic fish which inhabits the deeper part of large streams and rivers along the base of Western Ghats. Under riverine condition, this fish is reported to attain maximum size of 78 cm in length and 8 kg in weight. However, recent surveys revealed that as of now, only 0.5-1.8 kg size groups are available, though less in number. The fish is considered to be the only endemic fish consuming aquatic weeds and submerged grasses and could be used in controlling aquatic vegetation in reservoirs, tanks and irrigation canals. Though herbivorous, it is known to change its feeding habits depending up on the availability of food.

In natural waters, the breeding of P. pulchellus reported to commence soon after the monsoon months from September which continues until April with a peak in September and January. However, under pond culture conditions, it attains first maturity during June/July and breeding continues till October of the same year. Induced breeding of this fish has been successfully done by ICAR-CIFA.

Seed Production

Broodstock management

The male and female weighing not less than 800 g are stocked in earthen pond having a minimum water depth of 2 m at a stocking density of 2000/ha, three months prior to breeding season with provision for regular health checks and management of water quality. The pulchellus prefers clear waters with ideal water quality parameters. It is advisable to provide aeration to the pond, as slight lowering of DO, especially during morning hours, often results in heavy mortality of the stocked fish. The ponds are manured initially with cow dung @ 2-4 t/ha, 7-10 days prior to stocking. The fish is fed with a formulated diet having 35% protein. As the fish has a shoaling tendency and swims in groups, it is easy to observe the fish and record any abnormal behaviour or swimming pattern.

Selection of brooders

The fish cultured in pond attain first sexual maturity at 1.5-2 years of age and for breeding, it should attain a weight of at least 1 kg. It has a prolonged spawning period and the fish is observed to spawn four times in a year (batch spawner) during a particular breeding season. Hence, the number of ova released at each spawning is limited.

The fish is observed regularly for sexual maturity by periodic samplings. It is easy to select brooders for induced breeding programme as sexual dimorphism is exhibited very distinctly by mature male and female. Male during breeding season is distinguished by dark colour, especially at the abdominal region and pinkish-red prominent tubercles on the snout between the eyes, in contrast to the white and swollen belly, plain and smooth snout and swollen pinkish vent of female which however, had a deep pink lateral band. Male gonadal maturity can also be judged by the production of milt, which gets expressed on application of slight pressure on the lateral sides of the abdomen near the vent. The appearance of tubercles in male is seasonal and disappears after 3-4 months of its onset. Many a times, an immature male is mistaken for a female because of the absence of the tubercles as it appears only during the breeding  season. The success  of the induced breeding mostly depends on selecting a breeder at its prime stage of maturity.

Pink snout with tubercles & Plain snout of female

Dark colour at the abdomen & Swollen belly

Spawning

It is successfully bred with synthetic hormones like Ovatide/ Wova FH administered by injection twice to female and male on subsequent days. The first injection of the hormone preparation is given to both sexes at a dosage of 0.5 ml/kg body weight. All injections are given intramuscularly between the base of the dorsal fin and lateral line by lifting the fish scale to insert the needle and after injection and withdrawal of the needle, the area is gently massaged to aid distribution of the hormone into the musculature and to prevent any backflow. The injected brooders are released to the breeding pool of a hatchery and are allowed to remain there with circulating water and overhead shower running throughout. After 16-18 hours, when the belly of the female became soft and swollen, the second dose of hormone is injected to both male and female at the same dose given earlier. After 18-20 hours of the second hormone administration, the fish is anaesthetised by submersing it in 25 ppm solution of clove oil (5 ml of clove oil: ethanol mixture (1:4) is dispersed in 40 l of water) till their opercular movement becomes slow and the fish becomes non-responsive to touch. Then the fish is dry stripped. At first, the female fish is taken, wiped gently with dry and clean cloth and held in an inclined position with the head up and the ventral portion over the basin and gently applied slight pressure with the thumb and index finger on the swollen belly, slowly descending towards the lower end of the body down to the vent. The fully mature female normally releases stream of ripe eggs which flow out as a jet under this pressure. The faecal matter and blood, if any, coming out of the fish should be avoided as much as possible. The eggs flowing freely upon the application of gentle pressure at the lateral side of the abdomen indicates that the eggs are fully mature. Immediately after stripping the eggs, the procedure is repeated with the male and the milt is directly stripped on the eggs. The eggs and milt are mixed by slow orbital rotation of the basin for a period of 10 minutes facilitating fertilisation of the eggs. Alternatively, the gametes are mixed with the help of a feather. The eggs are then washed with freshwater, till the washings become clear of the milt.     

The fertilised eggs appear bright orange in colour. The released eggs measured 2 mm in diameter which upon fertilisation increase to 2.75-3 mm in diameter. This fish is a batch spawner and a fully mature female on first spawning releases about 10000-12000 eggs per kg body weight.

The fish on second spawning during the same season releases relatively less number of eggs, 5000-8000 per kg body weight.

Fertilized eggs

Incubation

The fertilised eggs are transferred to a hatching unit specially designed for heavy-yolk laden eggs, consisting of a series of rectangular FRP tanks with plastic trays inside with continuous flow of water on a re-circulatory mode with necessary biofilters to ensure good water quality. The DO, pH, hardness, temperature and alkalinity of water are of utmost importance for egg development and its hatching. The recommended values are

• pH           : 7.0-8.5;
• Alkalinity : 80-150 ppm;
• Hardness : 50-150 ppm;
• DO          : >5 ppm
• Temperature : 26-28°C.

Each tank houses a plastic tray with synthetic net bottom (1 mm mesh) immersed in water. The fertilised eggs are spread uniformly on the trays and water level of 5 cm or above should be maintained over the eggs and it should be ensured that there is an uninterrupted flow of water over these eggs to prevent clustering of eggs, which is very crucial for the development and hatching of eggs. The eggs attain a size of about 3 mm in 48 hours. At this stage the eggs become translucent and the twitching larvae can be clearly seen inside when examined under an inverted microscope.

Hatching trays & Hatchling

Larval development

The development of embryo is slow with the elongation of the yolk mass which takes about 24 hours. Sporadic twitching movement of the embryo is observed only 4 hours before the larvae is hatched from the egg shell and by this time the egg had swollen to a size of 3 mm and appears quite transparent under a microscope. As the embryo advances in its development, the movements become more vigorous. The hatching takes place within 48-72 hours post-fertilisation at 22-24 ^oC. The newly hatched larvae are transparent with no chromatophores, pale orange in colour with a heavily laden yolk sac. Though the embryo at this stage had clearly differentiated head and tail regions, they are not yet free from the ovoid yolk mass. These larvae move sporadically with a propelling movement. After 24 hours of hatching, the eyes are observed which appear to be faintly dark with a central pigmented area surrounded by a colourless rim. Anterior part of the yolk sac appear globular with a narrow smooth ending. The anal pore appears as a depression where the yolk sac ends and the larva attains a total length of 5 mm and weight of 4 mg at this stage. The yolk appears pale orange in colour. The head and tail are colourless (transparent) and the mouth is clearly visible and the eyes are heavily pigmented. Anal depression too is well marked. The yolk appears oblong in shape and ends abruptly. Complete yolk absorption in the larvae takes place by 6 dph at 24-26 ^oC.

Rearing of hatchlings

For better survival, the larvae after yolk absorption on 6 dph is kept in glass aquaria @ 2000/m³ at 26°C with constant aeration. They are fed with filtered zooplankton for a period of 5 days followed by a combination of filtered zooplankton and finely ground pelleted feed containing 35% protein as additional supplementary feed for another 10 days. The spawn immediately after shifting to the aquaria aggregates at the dark corners with little movement, but after a couple of days starts moving around and can be observed in all areas within the aquaria. The dead larvae, if any, along with other uneaten feed and faecal matter at the tank bottom should be removed daily before feeding. On every third day, one third of water from the tank is removed and replenished with fresh water. Ideal conditions of water quality as mentioned earlier should be maintained during this larval rearing phase also as slight deterioration in the water quality parameters usually result in mass mortality of the larvae. The fry thus obtained 15 days after hatching is transferred to nursery tank/pond for further rearing.  

Rearing of fry

Cement tank with soil bottom is initially fertilized with a mixture of 750 kg groundnut oil cake, 200 kg cow dung and 50 kg single super phosphate per hectare. A day prior to stocking the fry, soap-oil emulsion is applied to tank water for killing the aquatic insects and their larvae. The fry from aquaria is transferred to these tanks at a stocking density of 45/m² for further rearing into fingerling stage. The fry is fed with a mixture of rice bran and powdered groundnut oil cake (1:1) for the first month @ 10% of the body weight followed by fishmeal based 2 mm pelleted feed having 35% protein @ 8% of the body weight for the second month and @ 6% of the body weight during the third month. While the mixture of rice bran and groundnut oil cake is broadcasted in powdered form on the water surface, the pelleted feed is given in plastic trays, once daily, preferably in the morning hours. Feeding ad libitum in plastic trays resulted in faster growth in tank. As this fish prefers clean waters, subsequent fertilization of rearing tank is generally not recommended as the tank become green due to unconsumed feed and faecal matter of fish. The fry of 1.2 cm stocked at 45/m² attains a length of more than 5 cm at the end of 3 months reared in soil based cement tank.

Source : Department of Fisheries, Government of Kerala