Abstract
The comparative studies on the biology and culture of the freshwater mud eel (Monopterus cuchia) and the freshwater spiny eel (Mastacembelus armatus) of the Mymensingh region have been carried out during May 2000 to November 2002 in the Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. For morphometric and meristic, counts of 261 and 217 specimens of M. cuchia and M. armatus respectively were made for males and females of both the species separately. An application of 'Z' test showed no significant difference between the male and female of the eel species. The values of length-weight regression for males and females for both the eel species were practically identical and very close to the ideal 3. The relative condition factor (Kn) values were determined for males and females of both the species separately, according to size and month. The relation between the total length and weight of male, female and sexes combined of the mud eel and the spiny eel were found to be isometric growth pattern. The haematological parameters of both the species, like, total erythrocyte count, haemoglobin concentration, haematocrit values and neutrophils count were significantly (p<0.05) higher in males than the females during summer (on-set of breeding season). Females were observed to have remarkably higher values (p<0.01) of erythrocyte sedimentation rate, total leucocyte count and thrombocyte count during summer. The reproductive biology of the mud eel and the spiny eel have been described in terms of sexual dimorphism, gonadosomatic index (GSI), ova diameter and fecundity. It was observed that these species could be sexed on the basis of body colour during the breeding season. GSI values showed peak during June (5.50, in male and 7.52, in female) and July (8.40, in male and 10.58, in female) in the mud eel and spiny eel respectively. Monthly ova diameter measurement for both the species showed a progressive increase upto 4.0 mm and 1.0 mm for mud eel and spiny eel respectively. The mean fecundity was determined for mud eel and spiny eel to be 995 eggs and 4907 eggs respectively. The fecundity-gonad relationship (Log F = 0.33+ 2.31 x Log GW) and fecundity-total length relationship (Log F = -1.74 + 3.30 × Log L) showed better performance as compared to other variables in the mud eel and the spiny eel respectively. The results of culture experiment have been described in terms of effect of different food items, different shelters and stocking densities on growth and survival rate of the mud eel and the spiny eel. It was noted that among the food items mud eel preferred dead small fish and spiny eel liked dead small shrimp. Water hyacinth and PVC pipes were found to be the suitable shelters for the better growth and survival of the mud eel and the spiny eel respectively. Among the different densities the mud eel gave better growth and survival with higher stocking density (100 fish/1.25 m2), while the spiny eel gave better growth and survival with lower stocking density (20 fish/2.5 m2).