Suitability of Using Duckweed as Feed and Treated Sewage as Water Source in Tilapia Aquaculture (original) (raw)
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Suitability of Uisng Duckweed as feed and treated sewage as water source in tilapia aquaculture
Feasibility of using both treated effluent and duckweed biomass from a pilot-scale UASB-duckweed ponds system treating domestic sewage was evaluated in rearing Nile tilapia (Oreochromis niloticus). The nutritional value of duckweed was compared with wheat bran, used as a local fish feed ingredient, by applying these as the only source of feed for tilapia juveniles weighing 20 grams initial mean body weight. Two sources of water were used for each feed trial, treated-sewage and freshwater. The experiment was conducted in parallel with a conventional settled sewage-fed fishpond stocked with tilapia. Results of growth performance demonstrated that, in case of freshwater ponds specific growth rate (SGR) of tilapia fed on fresh duckweed was significantly (p < 0.01) higher than the SGR in wheat bran fed pond. No significant difference (p > 0.05) was observed between the two feeding regimes in case of treated sewage-fed ponds. The SGR of tilapia reared in the treated sewage-wheat bran-fed pond (TWP) was significantly higher (p <0.01) than the SGR in the freshwater-wheat bran-fed pond (FWP). On the other hand, due to the early spawning in the treated sewage-duckweed-fed pond (TDP) SGR of tilapia in the latter was significantly lower (p <0.05) than the SGR in the freshwater-duckweed-fed pond (FDP). The results demonstrated that duckweed-fed ponds provide higher net fish yield (11.8 ton/ha/y in TDP and 9.6 ton/ha/y in FDP), than wheat bran-fed ponds (8.9 ton/ha/y in TWP and 6.4 ton/ha/y in FWP). The fish yields in the ponds fed with treated sewage were higher than those in the ponds fed with freshwater. Negative net yield was observed in the settled sewage-fed pond (SSP) at -0.16 ton/ha/y. The negative results obtained in this pond, were attributed to the high mortality of 60% in the adult fish and 38% in the fry during the autumn. The best result was obtained in the treated effluent-duckweed-fed fishpond, providing 11.8 ton/ha/y net yield, which shows the potential value of both treated sewage and duckweed in aquaculture of tilapia.
Use of Domestic effluent through duckweeds and red tilapia farming in integrated system
Pan-American Journal of …, 2010
The present study aimed to evaluate duckweeds for wastewater treatment and as an alternative dietary feed source for tilapia in a reuse pilot system. Duckweeds presented a satisfactory pollutants removal, mainly for chlorophyll "a" (99.9±2.7%), suspended s olids (67.2±13.6) and turbidity (90.3±20.0%), reaching adequate criteria for aquaculture (nitrite, nitrate and COD concentrations under acceptable levels). Duckweed average production registered could reach up to 38.17 t/ha/year (dry matter), with a crude protein and fiber content of 38.03% and 16.17%, respectively. Fish fed on commercial feed presented higher growth performance compared to fish fed on dried duckweed. Final weight, feed conversion rate and specific growth rate of tilapia fed on dried duckweed were 52.5g, 4.3 and 1.17%, respectively. For commercial feed, the values found were 85.7g, 2.6 and 2.24%. Microbiological analysis confirmed that fish reared in treated wastewater were free of pathogenic organisms. Therefore, production of duckweed in wastewater can be an alternative which contributes to the sustainability of sewage treatment plants, mitigating environmental impacts. Also, it can be an alternative dietary source for tilapia, reducing feeding expenses as a mixture of dried duckweed and commercial feed (1:1) could reduce its production costs.
Resource recovery from septic tank effluent using duckweed-based tilapia aquaculture
Environmental Technology, 2012
Two parallel duckweed ponds were deployed to utilize nutrients from the effluent of a septic tank treating domestic wastewater. The effluent and fresh biomass of duckweed pond were fed to two subsequent fish ponds stocked with Nile tilapia (Oreochromis niloticus). Fish ponds receiving freshwater and commercial feed were used as control. The results of specific growth rate and feed conversion ratio showed no significant difference between the control ponds and treatment ponds. On the other hand, the total and net fish yields were significantly higher in the control. Microbial analysis revealed contamination of gills, intestine and liver of fish in the treatment ponds. The activity of the immune response genes was up-regulated in the brain and liver of the treatment samples. A micronucleus assay revealed a similar percentage of micronuclei in the polychromatic erythrocytes of blood in the control and treatment samples, while the treatment samples a had higher incidence of micronuclei in the polychromatic erythrocytes of gills, compared with the control.
The present experiment aimed to investigate the effect of organic fertilization and artificial feed, beside the addition of some untraditional feedstuffs as well as Biogen® to artificial feed on reducing feeding costs in tilapia culture. Twelve earthen ponds with the same area were stocked by Nile tilapia and represented 6 treatments (2 replicates for each). In the first treatment (T1), ponds were fertilized by 25 kg/day poultry litter throughout the experimental period (6 months). The same organic fertilization was used in the second treatment (T2) for 3 months followed by artificial feed (25% crude protein) during the following period (3 months). For the third treatment (T3), organic fertilization was applied during the whole experimental period and the artificial feed (2% of fish biomass) was applied during the last three months only. For the other three treatments (T4, T5 and T6) organic fertilization was applied for 3 months followed by feeding on artificial feed (25%CP) beside blue green algae, Azolla or Biogen® at a rate of 10, 10 and 2 kg/ton, respectively. Results of the experiment could be summarized as follows:
Fisheries and Aquatic Sciences
Small-scale fish farmers in developing countries are faced with challenges owing to their limited information on aquaculture management. Nile tilapia farmers in Teso North Sub-County recorded lower yields than expected in 2009 despite having been provided with required inputs. Water quality was suspected to be the key factor responsible for the low yields. This study sought to assess the effects of earthen pond water physico-chemical parameters on the growth of Nile tilapia in six earthen fish ponds under semi-intensive culture system in Teso North Sub-County. The study was longitudinal in nature with pond water and fish being the units of analysis. Systematic sampling was used to select five ponds while a control pond was purposively selected based on its previously high harvest. Four ponds were fed by surface flow and two by underground water. Each pond was fertilized and stocked with 900 fry of averagely 1.4 g and 4.4 cm. Physico-chemical parameters were measured in-situ using a multi-parameter probe. Sixty fish samples were randomly obtained from each pond fortnightly for four months using a 10 mm mesh size and measured, weighed and returned into the pond. Mean range of physico-chemical parameters were: dissolved oxygen (DO) 4.86-10.53 mg/l, temperature 24-26°C, pH 6.1-8.3, conductivity 35-87 μS/cm and ammonia 0.01-0. 3 mg/l. Temperature (p = 0.012) and conductivity (p = 0.0001) levels varied significantly between ponds. Overall Specific Growth Rate ranged between 1.8% (0.1692 g/day) and 3.8% (1.9 g/day). Ammonia, DO and pH in the ponds were within the optimal levels for growth of tilapia, while temperature and conductivity were below optimal levels. As temperature and DO increased, growth rate of tilapia increased. However, increase in conductivity, pH and ammonia decreased fish growth rate. Temperature and DO ranging between 27 and 30°C and 5-23 mg/l, respectively, and SGR of 3.8%/day and above are recommended for higher productivity.
Dried duckweed and commercial feed promote adequate growth performance of tilapia fingerlings
Revista …, 2008
The present study evaluated Nile tilapia when fed on dried duckweed in combination with commercial feed, aiming at reducing production costs. Three diets, which consisted of commercial feed (40% crude protein), dried duckweed or a combination of commercial feed and dried duckweed were fed to triplicate groups of 20 tilapia (Oreochromis niloticus) fi ngerlings. Fish weighing 3.2 ± 0.94g were stocked in nine 1-m 3 net cages and fed twice a day for 50 days. The fi nal average weights of fi ngerlings fed commercial feed (21.67g) and 50% feed + 50% dried duckweed (19.53g) were not different (p<0.05). Likewise, the specifi c growth rate did not differ between fi sh receiving these dietary treatments. Weight gain decreased as water temperature decreased along the experimental period, increasing feed conversion mainly for fi ngerlings fed on dried duckweed only. Also, when fed alone dried duckweed promoted the lowest weight gain and specifi c growth rate. It was confi rmed that dried duckweed can replace 50% (1:1 dry weight) tilapia fi ngerling 40% crude protein feed for a period of at least 50 days, without reducing growth.
Aquaculture Research, 1994
Oxidation treatment of sugarmill waste using duckweed {Lemna sp.) as part of the system, to reduce effluent nutrient concentrations and biological oxygen demand (BOD), was evaluated during a 6 month milling season in Negros Oriental, Philippines. Mean ammonia concentration in effluent water was reduced from 0-87 to 0-31 mg/l NHrN and orthophosphate from 0 93 to 0-51 mg/l PiOj, while mean BOD was reduced from 611 to 143mg/t BOD5, after treatment. Seasonal mass fish kills in the adjoining bay no longer occurred during the 3 years following introduction of this treatment. The mean duckweed production (dry weigiit) was 8-8g/m^/day. Duckweed was harvested from a 1 9ha area of the system and transferred to an adjacent milkfish, Chanos chanos Forskal, farm. Its fertilization effect, in terms of lablab production {lablab is the biological complex of bluegreen algae, diatoms, bacteria and various animals which forms a mat at the bottom or floats in patches), was evaluated in the mitkfish ponds. This was compared with ponds fertilized with either inorganic fertilizers or cow manure, in the traditional way. Lablab growth was significantly increased using duckweed, with ash-free dry weight production averaging 32g/m-/day following fertilization with duckweed compared with 4g/m^/day using inorganic fertilizers. Milkfish net production averaged 320kg/ha/90-day crop in inorganically fertilized ponds. 545 kg/ha/90-day crop tor cow manure and 820kg/ha/90day crop in duckweed-fertilized ponds. The system is described and the benefits of this integrated waste treatment-fish production facility are discussed.
Aquaculture Research, 2006
The e¡ects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low-cost cage-cum-pond integrated system for production of Oreochromis niloticus (L.). Hand-sexed male ¢ngerlings averaging19 AE 0.39 and 32 AE 0.69 g were stocked in cages and open ponds at 150 ¢sh cage À1 and 2 ¢sh m À 2 respectively. Fish were cultured for 114 days in ¢ve triplicate treatments. Cages were installed into ponds and caged ¢sh were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day À1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged ¢sh, which were fed 6% BWD for the ¢rst 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open-pond ¢sh fed. Feeding rate and pond fertilization signi¢cantly (Po0.05) a¡ected ¢sh growth, pro¢tability and water quality among treatments. Fish growth, feed utilization, ¢sh yield, water quality and pro¢ts were signi¢cantly (Po0.05) better in T3 than the other treatments. It was concluded that ¢sh production and economic returns were optimized at 6% BWD in fertilized ponds.