62 DECEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG role in improving the pH of the water body. Cut pieces of banana stem and leaves were effective in controlling clay turbidity and were being widely practiced in hill zones of Assam, India (Kalita et al. 2004). In addition, cut pieces of banana stem and leaves are used by fish farmers in Tripura to control turbidity and humus gas produced from bottom sediments in fishponds (Das et al. 2013). However, the banana stem strips and leaves had to be removed before they started rotting to avoid depletion of dissolved oxygen in the fishponds, which may have had adverse effects on fish stocks. Innovative Transportation Strategy of Carp Seed in Bamboo Baskets This innovative technique of transporting carp seed (fry/ fingerlings) in large cylindrical bamboo baskets lined with nylon sheets (Figs. 4a and 4b) is practiced by Naba Sarma, a progressive fish breeder from Panikhaity, Kamrup Metro district, Assam. Fry/ fingerlings were stored in a cylindrical bamboo basket with an inner lining of nylon (polyamide) sheet and transported in a mini-van. This basket, known as a duli in Assam, has been used traditionally by farmers of the state for storing paddy rice. A medium-size basket usually measures 1.5 m in height and 1 m in diameter. Water depth of around 1 m was maintained in the basket. The water volume of one such basket was approximately 3000 L. It could be used to transport 3500-4000 carp fingerlings of approximately 10 cm in length. Fingerlings carried in such baskets were transported to Damalbeel in Morigaon district from Panikhaity, a distance of around 100 km, for stocking in cages installed by ICAR-CIFRI Regional Centre, Guwahati. The duration of the journey was 2.5 hours with only 10-15 percent mortality. During the entire transportation process, water in the baskets was splashed manually to increase the dissolved oxygen levels. When we asked the breeder why he preferred this open-container for fish seed transport over the prescribed seed transport in oxygenated plastic bags (Jhingran and Pullin 1988), he indicated that the cost involved was approximately 30-40 percent less in the large open bamboo containers. Constructing Floating Beds in Weed-infested Backyard Ponds Backyard ponds are a common feature in households of rural Assam. These ponds were used to culture fish for household consumption. However, one of the major problems perceived for fish systems offer good protection to reared fish stocks but increase the cost of aquaculture operations. Noise, visual scare devices, light, scarecrows and predator models are some of the common frightening techniques used to control predatory birds in aquaculture facilities. Mohammed Ali Hussain, a progressive fish farmer of Dalapani village, Koliabar, Nagaon district, Assam, devised a useful technique to control predatory birds, particularly egrets, on his aquaculture farm. This bamboo cage was a visual scare device and was a slight modification of the indigenous traps used to hunt egrets in the locality (Fig. 2). This trapezoid shaped structure was wider at the base and tapered toward the top. Split bamboo strips were fixed longitudinally to the main frame and made with stronger split bamboo strips. Four curved arches (inverted U shape) were prepared with split bamboo strips and were attached on four sides of the top opening. Nylon threads were also fitted diagonally at the top. The height of these cages should be such that nearly half of it is above the water level. A total of 3-4 such structures were placed in the swallow peripheral regions (<0.5 m depth) of an aquaculture pond of 0.14-0.16 ha area. The farmer reported that these devices frighten predatory birds away from his aquaculture ponds. Application of Banana Stems and Leaves to Maintain Water Quality Ajit Barun Das, a fish farmer of Dighorshrikona village, Tatang, Cachar district, Assam, used split strips of banana stem and leaves to improve water quality in his aquaculture pond. The use of banana stem strips and leaves improved pH, reduced turbidity and controlled humus gas in fishponds. Turbidity caused by suspended solids and phytoplankton bloom often led to deterioration of water quality in fishponds. Formation of gas bubbles on the surface water indicated humus gas formation related to an excess sediment load in the pond bottom, thereby causing stressful conditions for the fish. The farmer applied split banana stem strips and leaves, which floated over the pond water surface (Fig. 3). These banana stem strips and leaves were removed from the pond from time to time and replaced by new ones. It was reported this innovative technique was effective in ridding such stressful conditions. Banana stem juice is a rich source of potassium. Hariharan and Manimaran (2014) reported the potassium concentration was highest (901 mg/L) among all the micro-elements present in banana shoot juice. The high potassium content in banana shoot juice played a key FIGURE 2. A visual deterrent against birds constructed of bamboo. FIGURE 3. Pieces of banana stem to control turbidity.
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