CONDUCTANCE OF SOME HEAVY METALS AS AFFECTED WITH THE APPLICATION OF RICE STRAW IN EARTHEN FISH PONDS
Naglaa I. M. Shalaby1 and Neima A. Ali2
1Limnology Dept. 2Fish Ecology and Biology Dept. Central Laboratory for Aquaculture Research, Agriculture Research Center, Giza, Egypt.
| Received 6/ 1/ 2019 |
Accepted 10/ 2/ 2019 |
Abstract
The present work was conducted over a fish culture season during the period from May to December/ 2017 to investigate the effect of rice straw, which applied in earthen fish ponds to enhance periphyton production and phytoplankton biodiversity; on some heavy metals values in pond water as well as their bio accumulation in some organs of O. niloticus. Six earthen ponds (1000 m2 surface area with 1 m water depth) belongs to the World Fish, were divided into two groups, each with three replicates; the 1st group was a control (C) while the 2nd (T) received 45 kg dry rice straw/pond. All ponds cultured with mono six Nile tilapia fry (0.1 g) in the rate of 3 fry/ m3. All ponds were fertilized with dry chicken manure with the rate of 15 kg/pond/week. Water samples were collected monthly from the water source (S) as well as from ponds of the two groups (C and T). Fish from all ponds were harvested and dissected to obtain muscles and gills. Some heavy metals (Fe, Zn, Cu, Cd and Pb) were detected in water and fish organs samples. Obtained results revealed that the values of all investigated metals in the examined water (except lead which was un detectable) were significantly (P<0.05) lower in C and T groups than in the source water. Despite that results showed that the residues of investigated metals significantly (P<0.05) increased in the organs of O. niloticus adults raised in the ponds that received rice straw, but all these residues were lower than the maximum permissible limits mentioned by international organizations (FAO/WHO, 1989; WHO, 1995) subsequently the use of rice straw didn’t affect the manner of heavy metals accumulation in different organs of O. niloticus.
