DUCKWEED AS A BIOLOGICAL FILTER IN TILAPIA FISH HATCHERIES AND ITS IMPACT ON TILAPIA REPRODUCTION
Ahmad A.A. Ali1; Yasser T.A. Moustafa2;
Soha M. Ahmed2 and Safwat A.A. Gomha3
1Fish physiology and hatchery Dept.; 2Limnology Dept.; 3Aquaculture Dept.
Central Lab. for Aquaculture Research (CLAR) Agricultural Research Centre (ARC), Egypt.
| Received 5 /1 /2020 |
Accepted 2 /2 /2020 |
ABSTRACT
Due to the decrease of freshwater in the current period, tilapia hatcheries depend on the agricultural drainage water. So this study was conducted on using duckweed as a biological filter in tilapia broodstock ponds. Nine concrete ponds were randomly assigned for 3 treatments; the 1st treatment as a control (without duckweed; 0 DW), the 2nd treatment received 200 g fresh weight of duckweed (200 DW)/pond stocked in a wooden frame, of 1m2 area (1 frame/pond), and the 3rd treatment received 400 g fresh weight of duckweed (400 DW)/pond stocked in two wooden frames, each of 1m2 area (2 frames/pond). All ponds were stocked with 68 Nile tilapia broodstock fish with an average weight of 225g/fish at a sexual rate of 3 females: 1 male. The experiment lasted for 15 days and replicated four reproduction cycles. Total ammonia, nitrite, nitrate, total nitrogen, particulate nitrogen, dissolved organic nitrogen and all fractions of phosphorus were measured in water ponds. Growth performance parameters of duckweed and fry production were also determined. The results showed that the 2nd (200 DW) and the 3rd (400 DW) treatments effectively improved the studied water quality parameters, increased fry production as access to by-product “duckweed” that may contribute in fish feeding and reduce the water consumption in tilapia hatcheries. Pearson correlation coefficients between the treatments and fry production proved significant positive relation. Interestingly, duckweed yielded an increase in fry production more than 13.5% compared to the control, as it doubled in biomass by 2.81% and 3.2% times, for 200 DW and 400 D, respectively, every 15 days.
Key words:
Oreochmois niloticus, duckweed, wastewater treatment, phytoremediation, Nile tilapia reproduction.
