THE IMPLICATIONS OF FISH AQUACULTURE ON THE QUALITY OF THE SEDIMENTS OF THE EARTHEN PONDS AT DELTA BREEDING STATION

Egyptian aquaculture has been started with the use of traditional extensive and semi-intensive techniques. rapid aquaculture development has occurred in recent years, after it had been identified as the best answer to reduce the increasing gap between supply and demand for fish. however, there is much concern about the increasing of the nutrient load and trace elements in sediment of earthen ponds due to the process of rearing fish of different sizes and ages. based on this statement, the present study was conducted to investigate the characteristics of the bottom sediments of the earthen ponds at the delta breeding station (dbs) and identifying problems raised from different activities especially that cause sediment pollution during rearing the fish, grass carp.results showed that the texture of the sediment in earthen pond was slightly similar. it ranged from sandy loam to loam. however, during rearing the grass carp in different sizes in the earthen ponds, the quality of the sediment has been widely changed after 3, 6 and 9 months from the stocking of fish. with increasing the period of stocking of fish in the earthen ponds, the values of ph have been statistically decreased, while the values of (ec), (hcoa-), (ca2+), (k+), (mg2+), (na+), (cl-), (no2), (noa), (nh4-h+), (po43+), (so42+) ions and the heavy metals (ba), (cd), (co), (cr), (cu), (fe), (mn), (ni), (pb), (v) and (zn) have been statistically increased. also the percentage of organic matter (o.m) increased. in addition, the sediments in earthen ponds which were stocked with the breeders of grass carp were characterized by having the higher values of anions, cations and heavy metals in the sediment more than the sediment of the earthen ponds which stocked with fingerlings of grass carp. this is mainly attributed to the feeding process.