ANNEX

Information on other hybrids

I. Interspecific hybrids of Indian major carps

i) L.rohita × L. bata (rohu-bata), L.calbasu × L.bata (kalbasu-bata) and L. gonius × L. calbasu (gonius-kalbasu) hybrids.

As in the case of the kalbasu-rohu and the reciprocal hybrids, the percentage of fertilization and embryonic development of these hybrid offsprings were normal, although the percentage of hatching was reported to be poor. Rohu-bata and kalbasu-bata hybrids did not show much promise, though the latter hybrid exhibited good initial growth.

II. Intergeneric hybrids of Indian major carps

i) Cirrhinus mrigala × L. rohita (mrigal-rohu)

A detailed, account of embryonic developments of mrigal-rohu hybrid, produced between female mrigal and male of rohu has been given by Basavaraju and Varghese, (1981). Unlike the case of the reciprocal hybrid, rohu-catla in which the fully swollen eggs of hybrid were bigger than those of the parents (Konda Reddy, 1977), in this mrigal-rohu hybrid the eggs were intermediate in size. Contrary to this, the commencement of cleavage in catla-rohu and rohu-catla hybrids as reported by Konda Reddy (1977) was intermediate, whereas in the case of the mrigal-rohu hybrid it was observed to commence later than the parent species (Basavaraju and Varghese, 1981).

The development of the mrigal-rohu, hybrid, in conclusion was normal and similar to that of the parent species. With regard to the morphological features, the hybrid exhibited intermediate traits between the parents. (Basavaraju and Varghese, 1981).

ii) C. catla × L. calbasu (catla-kalbasu) hybrid

Morphologically the hybrid has a greater resemblance with kalbasu in general appearance, indicating paternal dominance. The hybrid had a smaller head than catla and body girth greater than kalbasu. The quantity of flesh in the hybrid was also greater than in both the parents. The hybrid possessed a terminal mouth with thick lips. The feeding habits of the hybrid seem to be broadly varied as evidenced by the gut contents, comprising crustaceans, chironomid larvae, rotifers, diatoms, other algal forms, sand and mud. The hybrid also relishes artificial feed which was also observed in the gut in various stages of digestion. Thus the hybrid has a broader feeding spectrum and higher degree of adaptability for different food items from various niches of the pond.

The hybrid showed 66% survival at fry stage and at fingerlings, survival at the end of one year rearing in carp polyculture system was 40–80%. It attained a size of 330 mm/425 g as compared to 360 mm/680 g for catla. The growth of the hybrid under culture conditions was faster than kalbasu. Bhowmick et al. (1987) studied this hybrid in detail with regard to percentage of fertilization, growth, food and feeding habits, maturity and fecundity etc.. Prasad, 1976 reported the occurrence of L. calbasu and C. catla hybrid from the Rangwan Reservoir from the state of Uttar Pradesh in India (a natural hybrid).

iii) L. calbasu × C. catla (kalbasu-catla) hybrid

This cross between female L. calbasu and male C. catla did not yield any appreciable percentage of viable progeny. The development of eggs after insemination was abnormal and only about 20% of them hatched out, of which only a small percentage survived. However, further experimentation may be needed to arrive at definite conclusions.

iv) L. calbasu × Cirrhinus mrigala (kalbasu-mrigal) hybrid

This hybrid cross between female L. calbasu and male Cirrhinus mrigala showed normal fertilization with a 60% hatching rate. The hybrid had a slightly fringed lower lip and two pairs of prominent black barbels resembling that of maternal parent. Body color of the hybrid was intermediate between the parents species. No further details are available regarding the growth performance. However, the hybrids have been reported to attain maturity in 2–3 years.

v) L. rohita × C. reba (Rohu-reba) and L. calbasu × C.reba (kalbasu-reba) hybrids

These intergeneric hybrid crosses between female L. rohita and male C. reba did not result in any viable hybrids. Only about 20% of the hybrid zygotes hatched out but all the hatchlings died on the third day after hatching. Naseem Hamsa and Alikunhi (1971) also attempted to upgrade C. rebe by crossing it with the males of rohu, mrigal and grass carp. The hatchlings in all the three crosses were observed to be longer than those of C. reba. However, all the hatchling died within two days.

III. Intergeneric hybrids among Indian and Chinese carp

Hybridization was also attempted between, the species of the three genera, viz., catla, labeo and cirrhinus of Indian major carps and the three species of Chinese carps belonging to the three genera viz., Ctenopharyngodon, Hypophthalmichthys and Aristichthys. In all, nine intergeneric hybrids have been produced between Indian and Chinese major carps. Many of these hybrid progeny did not survive beyond one week excepting the catla-silver carp hybrids. However high mortality of the hybrids at embryo and larval stages was observed in catla-silver carp hybrid too, up to the fourth day. Many of the hatchlings were deformed particularly at the caudal peduncle region. In one experiment, only three hybrids could be reared up to three months, while in another only 16 surviving hybrids could be reared for a period of over two months and they grew to a size of about 57.7mm within this period (Ibrahim et al., 1980).

The percentage of fertilization was reported to be very high, ranging from 82–100%. (Ibrahim et al., 1980). Morphologically, the hybrid had a comparable body growth to that of catla. The size of the head and scales, including the body color were similar to silver carp.

In the hybrid progeny resulting from the mrigal × grass carp cross, the complete process of embryonic development including cleavage, segmentation etc. was quite normal and the hatching rate was over 90%. However, the larvae gradually became abnormal with a bent body and died within eight days after hatching (Ibrahim et al., 1980).

List of intergeneric hybrids between Indian and Chinese carp

IV. Intergeneric hybrids between Cirrhinus mrigala and C. carpio and thereciprocal cross

i) Cirrhinus mrigala × C. carpio (Mrigal-Common carp) hybrid

Kowtal and Gupta (1985) produced and evaluated intergeneric hybrid between Cirrhinus mrigala female and C. carpio male. These authors have reported a high rate of fertilization. However, about 40% mortality was recorded during embryonic and larval development. Only a few hybrids could be reared to adult size, i.e. to 242 mm/120g after 14 months rearing in nursery ponds.

The hybrid had a greater body girth than the maternal parent (mrigal) and a smaller head than in common carp. Though the outline of the mouth was similar to that of mrigal, it was protractile as in the paternal parent (common carp). The hybrid resembled common carp in having an elongated dorsal fin, moderately forked caudal fin and in scale and color pattern.

ii) C. carpio × Cirrhinus mrigala (common carp-mrigal) hybrid

As in the case of the common carp-rohu hybrid, in this cross the rate of fertilization was similar to pure common carp crosses. In embryonic and larval development the hybrid followed more or less the pattern of the maternal parent (common carp). Hatching commenced from 23.00 hrs after fertilization and was completed by 44–49 hrs. at 27–29 C.

Like the common carp-catla hybrid, this hybrid possessed a dorsally convex body with a slight hump as in common carp, but without the characteristic big belly of the mrigal. However, the body was more elongated and broader than mrigal. The terminal mouth of the hybrid was not protractile as in the case of common carp. Barbels, one pair of maxillary and the other mandibular were present. All this, the shape of snout (blunt) and the eye located in the anterior portion of the head, made the hybrid similar to the common carp. The traits resembling mrigal were the elongated body without big belly and non-protractile mouth and the pattern of lateral line.

The variable color of the hybrid, back greenish, sides golden yellow with a whitish ventral surface and greyish dorsal and caudal is an intermediate in appearances, at the same time the hybrid exhibits traits, which tend more towards the maternal parent, the common carp.

Regarding growth, the common carp-mrigal hybrid attained 48.2g under monoculture system, but it grew to only 10.2g in polyculture during the span of 110 days rearing. However, the parent species common carp and mrigal registered a weight of 107.4g and 110.8g respectively in the same polyculture system under similar rearing conditions. Thus the growth performance of this hybrid was slightly better than only mrigal (paternal parent), when the former was reared under monoculture (Khan et al., 1990).

V. Intraspecific hybridization in rohu (L. rohita)

Interspecific hybridization was also carried out among the members of stocks from different rivers which was termed as complete diallel crosses. (Gjarda et al., 1998). One with the stocks of River Ganga, Local (farm) and River Yamuna (Diallel-1) and the other with the stocks of River Brahmaputra, Local and River Sutlej (Diallel-2). The milt from each sire of each stock (5 sires/stock) was used to fertilize an equal amount of eggs from the females of the same or a different stock (8–10 females/stock).

The results of the two diallel-crosses indicated low average heterosis effects for both harvest body weight and survival. For diallel-2, significant negative average heterosis for body weight was observed in both mono and polyculture production systems. The results thus suggest that systematic crossing of rohu stocks may not yield any progeny with positive heterosis.

No. of crosses (Diallele 1)

No. of crosses (Diallele 2)

VI. Back-cross and triple-cross hybrids

A number of back-cross and triple cross hybrids have been also produced and studied among the hybrids of Indian major carps by crossing the hybrid females with normal males of parent species. The kalbasu-mrigal female hybrid has been back-crossed with the normal males of Labeo calbasu and mrigal resulting in kalbasu-mrigal-kalbasu and kalbasu-mrigal-mrigal back crossed hybrids. Similarly kalbasu-rohu hybrid female has been back crossed with the normal male of L. calbasu producing kalbasu-rohu-kalbasu hybrid (Ibrahim, 1977). Again rohu-catla female hybrid has been back-crossed with the normal male of L. rohita resulting in rohu-catla-rohu hybrid.

Back-cross hybrids have been also produced by crossing the female hybrid, produced between catla female and male of rohu, with the male of catla (F1 back-cross). Again when specimens of the F1 back-crossed hybrid were crossed among themselves (F2 back-cross) five interestingly phenotypically different types of individuals were noticed (Sarangi Personal Communication). In the photographs of these hybrids, some were found to be intermediate to catla and rohu even in body color while some others appeared very close to rohu. The study is being continued (Sarangi pers.comm.).

Two triple-cross hybrids have been also produced by crossing the female hybrid of kalbasu-mrigal with the male of C. catla thus resulting in kalbasu-mrigal-catla and the female hybrid of kalbasu-rohu with the male of Cyprinus carpio giving rise to the kalbasu-rohu-Cyprinus carpio.

Almost all these crosses have shown normal percentage of fertilization and hatching. The spawn/fry of these hybrids can be reared to adult size.

The back-cross hybrid kalbasu-rohu-calbasu exhibited a high percentage of fertilization reaching over 98%. The hybrid possessed a ventral mouth with a fringed lower lip and two pairs of barbels. The color of the hybrid resembled that of kalbasu. The yearlings of these hybrids (adults) were characterized by a smaller head and deeper body. In overall appearance, this back-crossed hybrid showed a close resemblance to kalbasu (Chaudhuri, 1971).

List of Back-cross and triple-cross hybrids