Heavy Metal Pollution Reduced the Potentiality of Pen Culture in the Wetland Aquaculture in an Urban Area of Bangladesh

The Belai beel serves as an important aquatic resource for the livelihood of the local community of the Gazipur district in Bangladesh. However, water pollution in recent times, mainly from industrial wastes and sewage effluents, may disrupt its aquatic environment. Thus, the purpose of the present study was to assess the potential area of pen fish culture in the Belai beel. The study was performed in the Rajbagan (L1), Kamaria (L2) and Rewla (L3) areas of the Belai beel. Grass carp, silver carp, common carp, catla and rui of 20–30 cm in size were stocked at a rate of 15,000 fish/ha and reared for 150 days in pens installed in the L1, L2 and L3 areas, respectively. The fishes were fed with mustard oil cake and rice bran. Maximum fish production was found in Rewla (12.97 ton/ha/150 days) compared to Rajbagan (8.85 ton/ha/150 days) and Kamaria (10.67 ton/ha/150 days) due to it having comparatively good quality water. There were significant differences in metal ion concentrations (p < 0.05) among the three fish pens. In the Rajbagan area, concentrations of Cd and Cu in the water coming from the industrial effluent canal exceeded the acceptable limit. Results indicated that the Rewla area was better than Rajbagan and Kamaria due to it having relatively good quality water for pen fish culture.

Growth performance of Tilapia (Oreochromis niloticus) cultivated in water from ex-sand pit lakes by phytoremediation treatments

Utilization of ex-sand pit lakes for aquaculture is difficult due to low water quality and high concentrations of iron (Fe). Phytoremediation using aquatic plants has been proven to be effective in reducing Fe in waters. This study aims to determine the growth, feed conversion efficiency and survival rate of tilapia (Oreochromis niloticus) cultured with ex-sand mining water media with phytoremediation treatment. Phytoremediation treatment was carried out by Eichhornnia crassipes, Azolla pinnata, and Salvinia molesta. Fish culture experiments were carried out in plastic tarpaulin tanks for 40 days, with ad satiation feeding, three times a day using the commercial feed. The results showed that phytoremediation with aquatic plants had succeeded in reducing Fe to a level suitable for fish culture. Fish culture experiments showed an absolute length growth rate of 0.09-0.18 cm/day and an absolute weight growth rate of 0.11-0.16 g/day. The feed conversion ratio was 1.18-1.40 and the survival rate was 98.04-99.08%. The survival rate of tilapia is high, the feed conversion ratio is medium and growth is low. The high environmental temperature and the decrease in water quality due to the absence of water changes and aeration are suspected of causing the low growth of fish. Therefore, further research with water change and aeration experiments and the use of other species of fish is needed to follow up the results of this study.

The Sustainable Treatment Effect of Constructed Wetland for the Aquaculture Effluents from Blunt Snout Bream (Megalobrama amblycephala) Farm

In aquaculture, constructed wetland (CW) has recently attracted attention for use in effluent purification due to its low running costs, high efficiency and convenient operation,. However, less data are available regarding the long-term efficiency of farm-scale CW for cleaning effluents from inland freshwater fish farms. This study investigated the effectiveness of CW for the removal of nutrients, organic matter, phytoplankton, heavy metals and microbial contaminants in effluents from a blunt snout bream (Megalobrama amblycephala) farm during 2013–2018. In the study, we built a farm-scale vertical subsurface flow CW which connected with a fish pond, and its performance was evaluated during the later stage of fish farming. The results show that CW improved the water quality of the fish culture substantially. This system was effective in the removal of nutrients, with a removal rate of 21.43–47.19% for total phosphorus (TP), 17.66–53.54% for total nitrogen (TN), 32.85–53.36% for NH4+-N, 33.01–53.28% NH3-N, 30.32–56.01% for NO3−-N and 42.75–63.85% for NO2−-N. Meanwhile, the chlorophyll a (Chla) concentration was significantly reduced when the farming water flowed through the CW, with a 49.69–62.01% reduction during 2013–2018. However, the CW system only had a modest effect on the chemical oxygen demand (COD) in the aquaculture effluents. Furthermore, concentrations of copper (Cu) and lead (Pb) were reduced by 39.85% and 55.91%, respectively. A microbial contaminants test showed that the counts of total coliform (TC) and fecal coliform (FC) were reduced by 55.93% and 48.35%, respectively. In addition, the fish in the CW-connected pond showed better growth performance than those in the control pond. These results indicate that CW can effectively reduce the loads of nutrients, phytoplankton, metals, and microbial contaminants in effluents, and improve the water quality of fish ponds. Therefore, the application of CW in intensive fish culture systems may provide an advantageous alternative for achieving environmental sustainability.

Physicochemical and microbiological evaluation of surface water quality of aquaculture ponds Located in Savar, Dhaka, Bangladesh

Aquaculture is one of the most vital sectors in Bangladesh as it exhibits a major role in nutrition, livelihoods and foreign exchange incomes/earnings every year. However, due to chemical impurities, infectious diseases caused by microorganisms, heavy metal accumulation, and aquaculture in Bangladesh is gradually declining and posing serious health risks. In Savar, which is one of the major industrial zones in Bangladesh, all industrial sewage and wastes severely deteriorate the water quality of the ponds, rivers, lakes and various waterways that are involved in aquaculture/fish culture. Hence, to determine the water quality by assessing different physicochemical and microbiological parameters, water samples were collected from five selected ponds located in Atomic Energy Research Establishment premises, Savar, Dhaka and analyzed according to the standard procedures. The obtained values of temperature, pH, Salinity, TDS, TA, EC, TH, Chloride content, Free CO2, DO, Nitrate and Sulfate were compared with the recommended values of Bangladesh and WHO standard for suitable water quality. Most of the physicochemical parameters exceeded the Standard value. Total Viable Count, Total Coliform and Fecal Coliform Count were also found to be higher than the standard value of WHO indicating fecal contamination of the pond water. Some fish pathogens were also isolated from the ponds. Water quality index (WQI) was calculated for five sampling sites to determine the level of pollution. It was observed that the water quality of the all the ponds reached to critical point of pollution. It is therefore, a high time to take initiatives to save the ponds that are involved in aquaculture from further pollution. The results revealed that the pond waters of five different sites were excessively polluted and unsuitable for fish culture.

Ecological Assessment of Fish Culture Water Bodies Around Dhaka City, Bangladesh

This study was conducted during the period November, 2014 - June, 2015 in two urban fish culture pond, at Kalshi and Namapara area of Dhaka city. These ponds are connected to Baunia canal. Water samples were collected seasonally for water quality and zooplankton analyses. Except DO all other measured water quality parameters (pH, TDS, TSS, total ammonia-N, total nitrite-N, total nitrate-N, total phosphate, total sulphate, alkalinity and hardness) were found higher in water. A total of 10 heavy metals (Zn, Fe, Pb, Cd, Al, As, Cu, Na, Mn and Cr) were measured for determining its concentrations in waters in two seasons. A total of 10 zooplankton species were recorded at Kalshi during the study period and on an average, the density of zooplankton in dry season and in wet season were estimated to be 1386 indiv./L and 244 indiv./L respectively. On the other hand, a total of 19 zooplankton species were identified from Namapara water body and on an average, the density of zooplankton in dry season and in wet season were estimated to be 1760 indiv/L and 343 indiv./L respectively. Bacteriological analysis included the total plate count (TPC), total coliform (TC) and total faecal coliform (TFC) counts in waters, both in wet and dry seasons. In general, water qualities of the studied fish culture water bodies are highly deviated from the permissible standard levels of Environment conservation rules, 1997 and unsuitable for fish culture from fish health point of view. The measured high levels of metals in waters are likely to bioaccumulate in fish body. High abundance of bacterial flora in fish culture waters is also likely to be associated with fish health and may cause enteric diseases. Therefore, fish culture in these urban water bodies is likely pose potential health risks for human through consuming these fishes. Bangladesh J. Zool. 49 (2): 267-276, 2021

Phytoremediation in Sandpit Lake: Aquaponic

Sandpit Lake in Sukabumi area is a suitable site for developing aquaculture. However due to rapid eutrophication only sustainable aquaculture should be applied. We evaluated the ability of lettuce in reducing nutrients from fish culture. This phytoremediation study was carried out using mesocosm, where lettuce as the phytoremediation agent were grown on vegetable floating raft (VFR) together with 25 fish which were grown underneath it and fed by fish feed. We built three sizes of VFR which were 20, 40 and 60% covered the mesocosm surface. The three sizes VFR were the treatment and the 0% covering served as control. Water quality sampling was carried out two times at day zero and day seven of the experiment. We collected temperature, oxygen, nitrogen, and phosphate data and analyzed them using ANOVA. Our result showed the nitrogen increased inside mesocosm meanwhile orthoposphat decreased. But the size of VFR did not give any effect to the water quality parameter change. However descriptively, we found that 40% of VFR was able to slowdown the nutrien TAN increasing and orthoposphat concentration found to be low. Moreover, it resulted in the highest lettuce survival. We recommend using 40% coverage in employing an aquaponic system in sandpit lake.