Agricultural Drainage Water as a Source of Water for Fish Farming in Egypt

Abstract

In Egypt, the reuse of agricultural drainage increases the country’s available water resources by 20%. The aim of this study was to assess the impact of agricultural drainage water on accumulation of heavy metals and pesticide residues of Nile tilapia (Oreochromis niloticus) reared in earthen ponds. Six earthen ponds (2 hectare for each) in two fish farms located at the same area (3 ponds for each farm). The first pond group irrigated by fresh irrigation water (IW) and the 2nd group (in another fish farm) supplied by agricultural drainage water (ADW). Each pond was stocked with 40000 fish (2.22±0.1 g) and fed on 25% CP diet at a daily rate of 3% of the total fish biomass. At the experiment end (7 months) results showed that, physico-chemical parameters for IW and ADW remained in the favorable range for Nile tilapia growth. ADW had higher density of phytoplankton and zooplankton in comparison to IW. Accumulation of heavy metals in liver and gills were higher than in muscles and ranked as liver>gills>muscles. Iron had the highest concentration values of metals content in liver, gills and muscles of fish reared in two water types and the sequence of metals was as follows: Fe&gtZn&gtCu&gtMn&gtPb. All pesticides residues under permeable limits in fish reared in the two types of water. Fish reared in agricultural drainage water showed the lowest significant (P<0.05) red blood cells (RBCs), haemoglobin (Hb), hematocrit and (Ht) total protein and the opposite trend was recorded for glucose and amino transferases, AST and ALT. ADW ponds produced the highest significant body weight, weight gain specific growth rate and fish yield compared to IW.