EFFECTS OF REDUCED FEEDING FOR COMBINED POLYCULTURE OF TWO MAJOR CARPS (ROHU AND CATLA) WITH SHINGH CATFISH (Heteropneustes fossilis)  

Air-breathing fishes provide a significant advantage for pond culture, as they tend to be resilient to harsh conditions, particularly during periods of low-oxygen, which can occur with high temperatures or drought. Currently, production of Shing (Heteropneustes fossilis, stinging catfish), a high valued cultivar, is limited to monoculture systems with intensive use of commercial-grade feeds (30-35% crude protein). As feed can comprise up to 60% of total production costs, the current practices for these fish limit participation by small homesteads and therefore comprise a significant impediment to further expansion of this industry. Further, the use of high-levels of feed inputs has led to a persistent deterioration of pond water quality.

An investigation was carried out to determine 1) if addition of Indian major carps (Rohu, Labeo rohita and Catla, Gibelion catla) alone can provide cost benefits for growout of Shing, and 2) if reducing feed by 50% and 75% from levels typically used by the industry to grow Shing might provide further cost savings in Shing-carp polyculture.  The study was carried out for 165 days in ponds at Bangladesh Agricultural University.  The experiment was consisted of four treatments (T1, T2, T3 and T4) with four replications each. The stocking density was 200 Shing/decimal, 32 Rohu/decimal and 8 Catla/decimal. All three fish species were stocked in all ponds except in the T1 group, representing the monoculture of Shing as control. Ponds under T₁ and T₂ were fed on full ration (20% - 5% body weight/day), while T₃ received feed at 75% and T₄ at 50% of full ration daily.

Growth and production of fishes did not vary significantly in the different treatments. The survival rate fish did not differ and ranged from 47 to 53% for Shing and > 89% for carps. The net productions of fish in T1, T2, T3 and T4 were 623±155, 3069±774, 3280±853 and 3171±805 kg/ha, respectively. Net return was -103,827, 294,485, 442,711 and 542,215 BDT/ha and benefit cost ratio (BCR, total returns/total costs) was 0.82, 1.55, 1.93 and 2.37 in T1, T2, T3 and T4, respectively. T4 showed the best overall FCR, SGR, BCR and fish yield followed by T3. In conclusion, the cost effectiveness of Shing growout can be substantially improved by addition of carps to the pond culture system. Moreover, reducing feed inputs by half provides additional benefits to Shing-carp polyculture.  Based on these studies, farmers have the potential to enhance their income opportunities by incorporating carps and reducing feed inputs in the growout of Shing.