Water retention capacity build up of fish ponds in North-West region of Bangladesh

Abstract

A research work on “Water Retention Capacity build up in North-West region of Bangladesh” was done from August 2015 to March 2019 at Paba Upazilla (Rajshahi University Campus area), Charghat upazilla and Bogura Sadar Upazilla. The main purpose of the research was to increase water retention capacity as well as improve fish production, monitor water quality and growth performance. Water retention capacity and production was improved by three different techniques viz. (i) digging and polythene lining with clay soil, (ii) digging and compost layering and (iii) only digging. Water quality and growth performance was monitored fortnightly with hackit box (DR-2010, USA), net, electric balance and scale. To set up experiment a total of 27 seasonal ponds in three locations (9 at Rajshahi University campus, 9 at Charghat-Bhagha and 9 at Bogra Sadar) were selected. The selected seasonal ponds are being dug at the level of 10 feet. Then all the prepared model ponds are being maintained 8 feet, 7 feet and 6 feet of water level for the treatmentsT1, T2 and T3 respectively in each site. To see the water retention capacity of constructed or re-excavated model ponds, fluctuations in water depths were recorded daily. Five farmer’s practiced ponds from each location were selected as control pond. During 1st year experiment (2017), 80 fingerlings/decimal and in 2nd year (2018) 61 fingerlings/decimal were stocked with similar species composition. The variable for all ponds was water depth of 8, 7 and 6 feet as same as previous year and were considered as Treatment1 (T1), Treatment2 (T2) and Treatment3 (T3) respectively. Feeds were given twice daily with commercial fish feed at 4% total biomass rate. Pond water depth of was recorded everyday using scaled PVC pipe fixed in pond. Growth of fish was monitored fortnightly. During the first experiment in 2017, water depth was found above 3 feet in five seasonal controlled ponds for 6 months in Paba (RU campus) upazila, 3 feet on an average period of 5 months at Charghat Upazilla and Bogura sadar Upazilla. Whereas model ponds lengthened round the year and the highest average water depths were 6.43 feet in T1 at Paba upazilla, 5.47 feet in T1 for 6 to 8 months at Charghat upazilla and in Bogura sadar Upazila 7.00 feet at T1 for the year round. In this experiment the mean water quality parameters both physical and chemical parameters were in the suitable range where there was no significant (p>0.05) difference in temperature, transparency, pH, DO and CO2 among the treatments. The harvesting period was in December. The highest specific growth rate (SGR) 1.33% was found in Paba and Charghat. ------