The experiment, studies on growth and production of a freshwater snail using different substrates in carp polyculture ponds, was carried out for a period of 3 months from May to July in 2009 at Field Laboratory Complex of the Faculty of Fisheries, Bangladesh Agricultural University (BAU), Mymensingh, and was designed with three treatments (T1 , T2 and T3 ) each with three replications which were assigned randomly among 9 experimental ponds. Each pond was of 140 m2 with an average depth of 0.76 m. Three treatments were allocated with three different types of substrates covering an area of 1 m2 in each pond. Whole cylindrical bamboo poles, split bamboo poles and palm leaves were assigned as substrates for T1 , T2 and T3 , respectively. Compost preparation Compost was applied in and around the substrate area of ponds, which acted as an important stimulant for growth of snail. The nutrients of compost enhanced the production of various food organisms such as invertebrates (e.g. chironomid larvae), periphyton and other microorganisms on substrates for snail. The manure also enhanced the primary productivity, i.e. plankton being natural food of carps in the pond. The manure was prepared on a dike of the experimental ponds in a lined pit with polythene sheet so that the nutrients of raw materials could not leach to the soil. Before stocking of snails, pre-stocking compost was made with an estimated requirement per m2 of pond area by mixing mustard oil cake (25 g m -2 ), cowdung (25 g m -2 ), urea (6 g m -2 ) and water hyacinth (12 g m -2 ). In the post-stocking period, other components, except cowdung, were halved to ensure required nutrient supply and to minimize operation cost. Pond preparation The experimental ponds were rain-fed and fully exposed to prevailing sunlight. At onset of the experiment, ponds were manually cleaned off aquatic vegetations. All unwanted aquatic animals were removed by rotenone application at the rate of 200 g pond-1 . Lime (CaCO3 ) was applied to all ponds at the rate of 250 kg ha-1 . Following this, ponds were filled with water from a nearby deep tube well. After a week of lime application, pre-stocking compost was applied in all research ponds at the rate of 680 kg ha-1 . Posting of substrates in the pond bottom Three different types of substrates were used for three treatments for growing of snail. In T1 , 9 (3x3 m -2 ) whole bamboo poles, collected from locally available sources, were posted in 1 m2 area of pond bottom. As with T1 , split bamboo poles (one fourth of a whole bamboo pole) were posted in the ponds' bottom of T2 . In case of the ponds of T3 , the same area as with other two treatments, were covered with a palm leaf. For making bamboo poles, a long bamboo was cut into several pieces of 1m long. After posting bamboo poles, the average substrate area of each bamboo pole was 1290.32 cm2 and total substrate area was 11612.88 cm2 m -2 of a pond. For making bamboo splits, a 1 m long bamboo pole was split vertically to make 4 splits. The average substrate area of each bamboo split was 706.71 cm2 and total substrate area for snail growing was 6360.37 cm2 m -2 pond. Locally available palm leaves were used as a substrate for snail culture as well. Each palm leaf consisted of 62-64 rows (average 62 rows), and the average area of each row was 633.87 cm2 , accordingly total substrate area for a palm leaf was 5704.83 cm2 m -2 of a pond. Following the posting of bamboo poles, snail (V. bengalensis) seeds were collected from a nearby canal and released at the rate of 60 kg ha-1 in all 9 experimental ponds. Stocking of carps The growth and production of snail were studied in carp polyculture ponds with the aim of getting additional benefits from snail production without hampering carps’ normal growth. Carps consisted of three Indian major carps - catla (Gibelion catla), rohu (Labeo rohita) and mrigal (Cirrhinus cirrhosus), and one Chinese carp - silver carp (Hypophthalmichthys molitrix). Carps were stocked at the rate of 20,000/ha with a ratio of 3 (catla): 2 (rohu): 2 (mrigal): 1 (silver carp). Feeding and manuring As the ponds were stocked with fish, the supplementary feed was given twice a day. A mixture of 50% rice bran and 50% wheat bran was applied as supplementary feed at 5% body weight of fish. At 15 days interval, compost was applied to ensure the growth of food organisms for snail. Sampling of snail and fish For measuring growth and production, snails and fish were sampled 3 times at 30 days of interval. The substrates of bamboo poles and bamboo splits were arranged in 3 x 3 lines, from which 1st sample was collected from 1st line at the end of 1st month, 2nd line at the end of 2nd month and 3 rd line at the end of 3rd month. Collection of snail from bamboo poles and bamboo splits were done very carefully so that snail did not drop in the pond. The sampled snails from the substrate of palm leaf were collected taking all the snails from randomly selected 3 rows of palm leaf. The sampled snails from different substrates were divided into 3 classes (small, medium and large) according to their length. The small class was of 0-15 mm, medium was 16-30 mm and large class was >30 mm in length. In every sampling, from each size class, randomly 3 snails were measured to get length and weight by spine compass, millimeter scale and electronic balance (CAMRY- Model: EK 3052, Precision = 0.01 g), respectively. As with snail, sampling was done using a cast net catching 10 fish from each pond. Length and weight of each fish species were measured using a millimeter scale and electronic balance, respectively.