Seasonal Changes in GSI, Fecundity and Biochemical Composition of Clarias batrachus (Linnaeus)

Abstract

To classify the biology of the Clarias batrachus, in Khulna region, sex ratio, monthly changes in GSI and fecundity were observed in the Laboratory. Male-female ratio of the studied species was 1: 0.94. Fecundity of the fish ranged from 1875 to 10798 in the total length ranged of 22.3-23:7 em. The fecundity is more directly related to the ovary weight. The regression line of fecundity in total length, standard length and gonad weight were all found to be linear and their co-efficient were all positive and significant at 5% level of significance. But the regression line of fecundity in body weight was negative. From their monthly dynamics in GSI, spawning seemed to have taken place somewhere between May to July with a peak in June for male and between June to August with a peak in June for female. Furthermore, GSI revealed that Clarias batrachus has a short spawning season. For different body parts, the protein content was higher in the middle portion of male (19.17± 0.303%) and in female it was (19.03 ± 0.131) in tail; the lipid content was higher in middle portion of male (1.19 ± 0.270) and female (l.10 ± 0.213). The percentage of ash content was highest in the head portion of male (12.88 ± 0.177) and female (12.20 ± 0.046), moisture content was highest in middle (79.31 ± 0.238%) and lowest in head (69.87 ± 0.270%) of male. For female the highest moisture content was in the middle (80.43 ± 0.15) and lowest was in the head (71.9 ± 0.136). Annual changes in nutrient content like protein, lipid, ash and moisture were assessed in the Clarias batrachus in both wet weight (body flesh) and dry weight (whole body) basis during the month May 2002 to Apri12003. The highest value of protein in the body flesh was found in October (21.75 ± 3.897%) for Male and in August (20.303 ± 0.040%) for female. The highest value of lipid was found in December for male (5.038 ± 1.314%) and for female the value was in the month of January (5.672 ± 0.064%). The highest value of ash was found in October (2.053 ± 0.632%) for male and September (1.825 ± 0.154%) for female. The highest value of moisture content was found in July for male (80.01 ± 0.085%) and for female the in was in the month of April (80.33 ± 0.129%). For whole body, the highest value of protein (19.322 ± 0.901%), lipid (7.761 ± 0.66%), ash (5.613 ± 0.532%) and moisture (79.13 ± 0.163%) was found in December, October, December and July, respectively for male. On the other hand, the highest value of protein (18.899 ±0.154%), lipid (5.10 ± 0.028%), ash (5.430 ± 0.037%) and moisture (76.72 ± 0.276%) was found in July, May, June and October, respectively for female fish. From the nutritional point of view it shows that the nutrient content of Clarias batrachus is undeniable compared to other small and large fishes.