EFFECT OF ARTHEN POND AREA ON WATER QUALITY, PLANKTON COMMUNITIES’ STRUCTURE AND NILE TILAPIA (OREOCHROMIS NILOTICUS) YIELD
Safwat A. A. Gomha
Central Lab. for Aquaculture Research, Agriculture Research Centre, Egypt
|Received 6/ 1/ 2014||
Accepted 18/ 2/ 2014
The present investigation was carried out for a 210-day period in an attempt to demonstrate the effects of different area (6000; (T1), 7000; (T2) and 8000 (T3) m2) of earthen fish pond (1.5-2 m water column) on water quality, plankton communities’ structure and Nile tilapia (Oreochromis niloticus) yield. These areas with two replicates each formed this experiment. The ponds were stocked at a rate of 4.26 ± 0.20 fries (male Nile tilapia (O. niloticus) with an initial body weight of 1.07±0.61 g/fish)/m2. Both water quality parameters and plankton communities’ structure were measured monthly. Resulted revealed that all measured water quality parameters were not affected significantly (P> 0.05) by the area of the earthen ponds. Also, their values were between the acceptable ranges. There were no significant difference (P>0.05) among treatments for all groups of both phytoplankton and zooplankton communities (except cladocerans group). The blue green algae and rotifers were the dominant groups for both phytoplankton and zooplankton, respectively. In general, it can be concluded that the increase of the earthen pond area, resulted in increased the green algae community percentage and the decrease of the blue green algae community percentage. T1 (6000 m2) had the highest general mean harvest of fish (2.50 ton fish/faddan) followed by that of T3 (8000 m2) (2.35 ton fish/faddan) and finally by that of T2 (7000 m2) (2.26 ton fish/faddan). The same trend was observed with T1 for final body weight (150 g/fish), daily weight gain (0.71 g/day), specific growth rate (2.39) and feed conversion ratio (1.78 kg/feed: kg/fish), where there was no significant differences (P>0.05) for all of their parameters among treatments. From the previous results, it is clear that the earthen pond area did not affect on all measured water quality parameters, majority plankton communities’ structures and Nile tilapia O. niloticus harvest for the unit of the production area (1faddan).