Abstract

Objective: To determine the impacts of three different low cost diets in monoculture system on the growth and production of indigenous catfish Shingi, Heteropneustes fossilis (Bloch, 1794) (H. fossilis) in earthen ponds. Methods: The experiment was carried out for a period of six months with three treatment groups (T1, T2 and T3) each having three replicates in the research ponds of Department of Fisheries, University of Rajshahi. Protein levels of formulated feed used in three treatments were 31% in T 1, 29% in T2 and 27% in T3, respectively. Stocking density of H. fossilis was 250 individuals/decimal in each treatment. At stocking, all fingerlings were of mean length and weight of (4.30 ± 0.01) cm and (4.20 ± 0.02) g, respectively. Fish growth and water quality parameters of the experiment were measured fortnightly. Results: The mean values of water temperature, transparency, pH, dissolved oxygen, free CO2, alkalinity and NH3-N of water varied from (22.08 ± 1.78) to (22.35 ± 1.76) °C, (27.09 ± 0.92) to (28.01 ± 0.82) cm, 7.44 ± 0.06 to 7.52 ± 0.06, (4.47 ± 0.10) to (4.53 ± 0.08) mg/L, (6.31 ± 0.33) to (7.05 ± 0.17) mg/L, (105.72 ± 2.97) to (109.11 ± 4.57) mg/L and (0.010 8 ± 0.002 0) to (0.011 2 ± 0.001 0) mg/L, respectively. Mean values of the water quality parameters showed no significant differences (P > 0.05) among the treatments. The net weight gain and survival rate were found to be (43.90 ± 0.42) g and (83.21 ± 1.43)% in T1, (37.50 ± 0.67) g and (79.28 ± 1.36)% in T2 and (34.30 ± 0.62) g and (78.95 ± 2.53)% in T3, respectively, which were significantly (P < 0.05) different among the treatments. The minimum value [(1.10 ± 0.22)%] of specific growth rate (SGR) was recorded in T3; whereas the maximum value [(1.35 ± 0.25)%] was recorded in T 1. The values of feed conversion ratio (FCR) of H. fossilis were found to be 2.68 ± 0.34, 2.31 ± 0.12, 2.22 ± 0.05 in T1, T2 and T3, respectively. Significantly higher weight gain, SGR and survival rate of H. fossilis were found in T1. The net production (kg/ha) was also found significantly (P < 0.05) different among the treatments. Net production in T1 (2 249.98 ± 10.66) was significantly higher than that in T2 (1 829.34 ± 4.50) and T3 (1 652.05 ± 16.69). Cost-benefit ratio (CBR) in treatment T1 in the present study was higher (1:1.91) than that in the other two treatments. Conclusions: The overall production of H. fossilis and CBR in T1 were significantly higher. From the study, considering water quality, production and economics, it is proved that the higher growth and survival rate of H. fossilis was found with 31% protein level of the feed in earthen ponds of Bangladesh.

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