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Hybridization of Rohu (labeo Rohita) and Bata (labeo Bata) and Growth Comparison of the Hybrid with Rohu

Md. Saifuddin Shah
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Alokesh Kumar Ghosh
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Abstract/ Executive Summary:

A sixty-day study was carried out to compare the growth of hybrid between Labeo rohita (rohu) and Labeo bata (bata) with one of the parental species, rohu. The fertilization and hatching rates found to be lower in hybrid than those in rohu. After three days of hatching the spawns were reared in earthen nursery ponds for sixty days. The growth in weight for the first ten days and, in weight and length for the following fifty days were obtained and compared with those of rohu and significant difference in the rates of growth were observed. The hybrid showed faster growth rate than the parental species, rohu. The results obtained could be considered as preliminary finding in rohu x bata hybridization and needs further work.

Keywords: Hybridization, Labeo rohita, Labeo bata

Location: Government Fish Seed Multiplication Farm, Gallamari

Start Date: 00-04-2007

End Date: 00-07-2007

Program Area: Comparative study

Commodity: Rohu, Bata

Objectives:

There are many examples which show that hybridization helps to improve productivity. Chappell (1979) and Islam and Shah (2007) find that some hybrids improve yield by 10-55%. The objectives of the present investigation were to produce a good quality F1 hybrid of L. rohita and L. bata and compare their fertilization and hatching rate and growth with those of the parental species, rohu

Methodology:

The experiment was performed in the Government Fish Seed Multiplication Farm, Gallamari during the period from April 2007 to July 2007. For induced breeding PG (pituitary gland) hormone of Indian major carp was injected to two pairs of spawners. Hybrid was produced by crossing male rohu and female bata. For females two doses of PG hormone at 2 mg and 5 mg kg-1 of body weight were applied at 6 hours interval. For male a single dose of PG Hormone 2 mg kg-1 of body weight was applied at the time of second injection to the female. The sex ratio of the spawners was maintained at 1:2 (male: female). Continuous water flow was provided in the tanks by showering of water. The spawners became ready for spawning within 5-6 hours of second injection when they were stripped carefully. Eggs stripped from the females were mixed well with the milt stripped from the respective males. The inseminated eggs were then transferred into the incubation jars providing with a continuous flow of water.

Fertilization and hatching rates: The rates of fertilization and hatching were recorded by individual counting of the fertilized eggs and hatched out larvae. The fertilized eggs were easily separated from the unfertilized eggs by the presence of transparent cover with gray/ black spots within the egg cover, while the unfertilized eggs were opaque and their number was counted. Some fertilized eggs were put into a hatching chamber made with a PVC pipe of three inches diameter, cut into pieces of six inches. The bottom end of the pipe was closed with fine meshed cloth and was made to float in the bottle hatchery jar with the help of polystyrene foam attached at the rim of the pipe. A few holes were cut on the surface of the pipe and covered with a thin cloth to let water flow in the chamber. Then hatching rate was determined as follows: - Hatching rate (%) = (No. hatched/ Total No. of fertilized eggs) X100

Spawn rearing and fry nursing: Two earthen nursery ponds measuring 1.25 dec each were used. Rotenone was applied at the rate of 25 g dec-1 to remove the unexpected fauna. The ponds were limed at the dose of 1.25 kg decimal-1. After five days of liming, fertilization was done by applying 2 kg mustard oil cake, ½ kg urea and ¼ kg TSP per pond (Anon, 2004). Stocking was done at the rate of 2000 spawn deci-1. The spawn were acclimatized in the nursery ponds before releasing them into the ponds. For 1st two weeks, mustered oil cake 100 g +urea 60 g +TSP 30 g were used as feeding. Next four weeks, mustered oil cake 200 g +urea 60 g +TSP 30 g were used as their feeding.

Growth: Sampling was done with the help of a seine net at every ten day intervals.. In the first sampling only the average weight of the fishes were taken. In the next samplings fry were measured in both weight and length individually. Sample fishes were anesthetized with 10% Benzokaine solution at a concentration of 1 ppt for the convenience of taking weight and length. An electronic balance with 0.1 mg and a centimeter scale with 1 mm denomination were used for weight and length measurement, respectively.

Source of Information: Khulna University Studies, 9(2): 215-220, 2008

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

A Hybrid of two different species often has a higher growth rate than a single species. In the case of inbreeding, heterozygosity is lost because of close mating. However, hybridization is a process by which heterozygosity in the progenies can be produced and thus hybrid vigor or heterosis is achieved. In the present experiment F1 hybrid of rohu and bata showed better growth than rohu. So, hybridization between the species may be done to overcome the inbreeding problem and to achieve heterosis for better growth and production in the aquaculture systems in the country.

Knowledge Management: Journal