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Optimizing the Stocking Density Is Crucial for Growth and Survival of Catfish, Clarias Batrachus Larvae

Sk. Mustafizur Rahman
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

S.M. Asaduzzaman
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Md. Nazmul Ahsan
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Q. Z. Hossain
Environmental Science Discipline, Khulna University, Khulna-9208, Bangladesh

Md. Mostafizur Rahman
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Md. Ayaz Hasan Chisty
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh

Abstract/ Executive Summary:

The effect of four (12, 18, 24, and 30 larvae L^-1) stocking densities (SD) on growth and survival of catfish, Clarias batrachus larvae (1.47 cm and 0.03 g) was investigated in triplicates in glass aquaria for a period of 28 days. The larvae were fed with Tubifex sp. four times daily until satiation. The larvae reared at high SD (30 larvae L^-1) showed significantly slower growth performance than those held at low SD (12 larvae L^-1). Water quality parameters were found within the productive range (temperature: 28.7°C, DO: 6.1 mg L^-1, pH: 7.8, and alkalinity: 379 mg CaCO₃ L^-1) for all treatments. The specific growth rate varied significantly in fish reared at high SD than at low SD on day 14 only, but on day 7, 21, and 28 there were no significant differences among the four treatments. Heterospecific growth was observed in high SD resulting in increased coefficient of variance of length and weight on final day. On the other hand, there was no effect of stocking densities on the survival rate of the larvae during the experimental period. Based on these findings, a stocking density of 18 larvae L^-1 appears to be optimum for intensive culture of C. batrachus in indoor static water system.

Keywords: Clarias batrachus, Stocking density, Growth rate, Survival

Location: Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Cat fish

Objectives:

To test the effect of high stocking density on growth and survival of eight days old C. batrachus larvae in aquarium tanks.

Methodology:

Brood collection and induced breeding - Mature healthy broods of C. batrachus were collected from the local market. Immediately after collection, broods were transferred to the fish rearing facilities at Khulna University and kept in a 500 L tank with aeration for 2 days. For this experiment, seven females and five males ranged from 130 to 190 g for male and 100 to 160 g for female were used. Spawning to obtain the larvae was induced following the standard procedure. Larval rearing - Eight days old larvae having an initial total length and weight of 1.47 ± 0.02 cm and 0.03 ± 0.001 g, respectively were reared in glass aquaria (50 × 30 cm; 20 L water) at a stocking density of 12 larvae L^-1 (SD 12), 18 larvae L^-1 (SD 18), 24 larvae L^-1 (SD 24), and 30 larvae L^-1 (SD 30) for 28 days. Each treatment was conducted with three replicates. Larvae were fed Tubifex sp. four times daily (8:00, 12:30, 18:00, and 22:00) until satiation. Aerator and PVC pipes were used to ensure oxygen supply and provide shelter, respectively for the larvae. Two PVC pipes of 7 inch long and 1 inch diameter each were used in each tank. About two-third of the water was replaced twice a day. During replacing water, feces, and dead larvae, if any, were removed. Adhered dirt inside the aquarium walls and PVC pipes were cleaned during water exchanges. Data collection - Weekly measurements were carried out for weight (to the nearest g) with an electric balance (Mettler Toledo, B303-S; accuracy 0.0000 g) and total length (to the nearest cm) with a measuring scale for about 30 larvae from each aquarium. The dead larvae were counted for assessing the survival. Length and weight gain, specific growth rate (SGR), coefficient of variance (CV) of length and weight and survival rate were determined according to the following formula: Length gain = Mean final length – mean initial length; Weight gain = Mean final weight – mean initial weight; SGR = {(Ln final weight – Ln initial weight)/culture period} × 100; CV of length = (Standard deviation of final length/mean of final length) × 100; CV of weight = (Standard deviation of final weight /mean of final weight) × 100 and Survival rates = (Number of live fish/total number stocked fish) × 100. Water quality parameters - Water quality parameters such as temperature, dissolved oxygen (DO), and pH were recorded twice daily during morning (08:00) and evening (20:00) in all tanks. Temperature and DO of each tank were recorded by a mercury thermometer and DO meter (Lutron DO-5510), respectively whereas the pH was recorded with the help of a pH meter (Hanna ISO 9001). Alkalinity of water was determined by titrametric method. Statistical analysis - All numerical results were expressed as mean ± SD (Standard Deviation). Significance levels were analyzed by one-way ANOVA followed by the Tukey’s multiple comparison tests. Differences were considered as statistically significant at a probability value of P < 0.05.

Source of Information: International Journal of Biosciences (IJB); ISSN: 2220-6655 (Print) 2222-5234 (Online); Vol. 2, No. 10(2), p. 103-109, 2012

Article Link (Online Journal): http://www.innspub.net

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In conclusion, the study clearly demonstrated that the growth of C. batrachus larvae in tanks is density dependent. Both growth in weight and length were negatively affected by increased stocking density. The maximum average growth rate was in SD₁₂ followed by SD₁₈, SD₂₄, and SD₃₀. Increasing densities result in heterogeneous growth rates and the suppression of growth of some individuals. In the present rearing trial, no effect of survivability was found fewer than four stocking densities. Considering overall growth performances, the 18 larvae L^-1 stocking level is proposed as the optimum density for intensive culture of C. batrachus larvae in tanks.

Knowledge Management: Journal