Abstract
The breeding biology, embryonic development, larval rearing and pond culture of endangered local sarpunti, Puntius sarana (Hamilton) were studied at the Fish Seed Multiplication Farm, Ishwargonj, Mymensingh and Fisheries Research Complex of Bangladesh Agricultural University (BAU), Mymensingh during April, 2000 to June 2003. Histological examination of the gonadal tissue of the gynogens indicated that the female was homogametic in term of sex determination. The P. sarana gynogen were all female. The highest amount of spermatozoa and matured oocytes was observed in May. With the development of gonad, the gonado-somatic index increased gradually with the maximum value of 2.47±0.08 in male and 4.09±0.09 in female during May. Histological analysis of gonads and GSI values at successive months revealed that P. sarana breed twice in a year.
The fecundity of P. sarana was estimated by gravimetric method and a highly significant (P < 0.01) linear relationship was found to exist between fecundity and gonadal weight. The equation was obtained to be: Y= 17053 + 853.63X. The value of co-efficient of determination (R2) was 0.899.
Four sources of hormonal substances were tested to evaluate their efficacy on ovulation, fertility and hatching rate of local Sarpunti, P. sarana eggs under controlled conditions. Single dose of Ovaprim (0.45 ml/kg) was found to be better than single dose of pituitary extract (6.5 mg/kg) and double doses of pituitary extract (1st 2 mg/kg and after 6 hrs interval 2nd 4 mg/kg) in egg maturation and ovulation. Human chorionic gonadotropin and Profasi did not respond to ovulation. Embryonic and larval developments of P. sarana were studied under laboratory conditions. At fertilization, the eggs were 0.8 mm in diameter. First cleavage was recorded within 35 mins after fertilization and the embryonic rudiments of developing eggs appeared at 9 hrs and 40 mins at 27.0 - 27.5°C. The yolk sac was completely absorbed at 66 hrs during embryonic development on attainment of 6.0 mm total length. At the same time, digestive system became fully developed and the larvae searched for feeding.
Gynogenesis was induced by fertilizing normal eggs with genetically inactivated sperm followed by heat shocking. The sperm were inactivated by exposing them to a UV-ray of 250 μw/cm2 for 2.5 mins at a concentration of 1 x 108 sperm/ml. Exposure of inseminated eggs to heat shock at 39°C for 2 to 4 mins after fertilization increased the yield of diploid gynogenetic offspring.
Nursery rearing of P. sarana was studied in relation to different supplementary feed and varying stocking densities for a period of six weeks in earthen ponds. The growth performances of local sarpunti (ADG, SGR and survivality rate) were found to be better at a stocking density of 0.7 million individual/ha when fed with a mixture of rice bran (40%), mustard oil cake (50%) and fish meal (10%). Stocking density had significant effect on the growth, survival and production of fish fry. The physico-chemical and biological characteristics of water were found to be in optimum ranges for the fish culture. P. sarana when stocked (initial at 4.49 g) at 24700/ha in monoculture yielded 2671.31kg/ha/in 6 month, with net return of TK. 65291/- indicating a BCR of 1.51. Production potential of P. sarana in the polyculture with Indian major carp and exotic carp were examined. In polyculture system, the fingerlings of P. sarana were stocked with Catla catla, Labeo rohita, Cirrhina mrigala and Hypophthulmus molitrix where the fish production in treatment T1, T2 and T3 were found to be 4876, 4062 and 4111 kg/ha/yr with net return were Taka 87,459/-, 63,858/- and 46,529/- in T1, T2 and T3, respectively. Puntius sarana contributed 8.68%, 12.07% and 12.03% to the total polyculture yield.
The technology of monoculture and polyculture system indicated that the cultivation of this barb was economically viable and the growth rate of P. sarana was higher in open water system.