The number of body segments ranged from 34 to 120 in Tubifex, 50 to 87 in Limnodrilus, and 35 to 100 in Aulodrilus. All these three genera possessed a cylindrical body with a bilateral symmetry formed by a series of metameres. These were Tubifex, Limnodrilus and Aulodrilus. The study result indicated the existence of three genera among the tubificid worms. A step was taken to identify the genera of tubicifid worms that exist in Mymensingh district, Bangladesh on the basis of some external features including the shape of their anterior (prostomium) and posterior end, number of body segment and arrangement of setae. The worms are very important as they are used as live food for fish and other aquatic invertebrates. Tubificids are aquatic oligochaete worms (F- Naididae, O- Haplotaxida, P- Annelida) distributed all over the world. It was concluded that introduction of sorting sieves to catfish hatchery will reduce drudgery in fry sorting while increasing percentage survival and profitability at the same time. Economic analysis of the trial gave Marginal Rate of Return (MRR) of N5.50k in favour of T1. At harvest (10th week), there were more numbers of small (4-6 cm) and large (8-12 cm) sizes of juveniles in T2 than T1 whereas numbers of medium (6-8 cm) size juveniles in T1 almost doubled that of T2 at a significant level (P ˂ 0.05). Survival rate from fingerlings to juveniles at the 10th week significantly (P ˂ 0.05) reduced to 62.33 ± 12.73% (T1) and 40.55 ± 8.44% (T2) respectively.

The percentage hatching was high, 78.33 ± 4.08% and 76.92 ± 3.19% in T1 and T2 respectively but not significant (P ˃ 0.05). Sorting of fish were done on the 14th, 21st, 28th, 42nd, 56th and 70th day after hatching. Fertilized eggs were shared weight for weight between T1 and T2 and normal management procedures were followed. Broodstocks of 1500 ± 10.52 g were used for breeding. T1 utilized sorting sieves while T2 used hand manual sorting. Two hatching troughs served as Treatment 1 (T1) and Treatment 2 (T2) in each farm. The trials were set up in six farms across the State. Sorting sieves were introduced into the hatchery management of Clarias gariepinus fry in Lagos State to improve on the survival rate and growth performance of C.

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