Contamination of the Egyptian Mediterranean Coast has become a subject of a great deal of research in recent years. The continuing and increasing release of a great number of industrial, agricultural, commercial and domestic waste effluents and emissions as well as hazardous substances have affected the characteristics of water [1] - [7] , sediments [8] - [15] , and fish which is most commonly chosen because of the implications it carries for human consumption and health risk [16] [17] [18] [19] [20] . Major concern has been directed to persistent organic pollutants (POPs) as they are highly resistant to degradation by biological photolytic and/or chemical means [21] [22] [23] . These compounds were found widespread in the environmental media, humans and wildlife, and globally distributed including remote areas where they have never been used [24] . POPs are used to refer to organic compounds whose presence in the environment in very small amounts can cause significant harm to ecological systems and/or humans [25] . This study was aimed to compare the concentration levels of POPs in tissues of Sparus auratus as the most economical marine fish species in the eastern and western sectors of the Egyptian Mediterranean Sea.

Biota samples, Sparus auratus species, were collected fresh from 12 stations by fishermen working in the Eastern and western sectors of the Egyptian Mediterranean Sea during 2010 (Figure 1), no more than 2 h after catching and then kept frozen in the laboratory. Biological specimens were dissected and their tissues were kept frozen until extraction. Fish tissue (10 g of wet wt. of flesh) as placed in a blender, and 30 g of anhydrous sodium sulphate was added. Samples were blended at high speed until the mixture was well homogenized (2 - 3 min). The mixture was then transferred to a pre-cleaned extraction thimble and the dehydrated tissue was extracted with 200 ml (1:1) of n-hexane-dichloromethane for 8 h in a Soxhlet apparatus cycling 5 - 6 times h⁻¹. Anhydrous sodium sulphate (30 g) was extracted in the same fashion as the sample and used as the blank. The extracted solvents were concentrated with a rotary evaporator and concentrated with a pure nitrogen gas stream down to a volume of 2 ml [26] [27] . Clean-up and fractionation were performed by passing the extract through a silica/alumina column. Elution was performed using 70 ml of hexane for PCBs congeners (F1), followed by elution with a 50 ml mixture containing 70% hexane and 30% dichloromethane for pesticide fraction (F2). Finally, eluted samples

were concentrated under a gentle stream of purified nitrogen to about 0.2 ml, prior to injection into GC/ECD for analysis. All samples were analyzed by a Hewlett Packard 5890 series II GC gas chromatograph equipped with a ⁶³Ni electron capture detector. The instrument was operated in split less mode (3 µL split less injection) with the injection port maintained at 290˚C and the detector maintained at 300˚C. A fused- silica capillary column; Thermo TR-35 MS (30 m, 0.25 mm, 0.25 μm) with 35% phenyl polysilphenylenesiloxane was used for the quantification. The temperature was programmed from 90˚C - 140˚C with rate of 5˚C min⁻¹, then held at 140˚C for 1 min, and from 140˚C - 250˚C with rate of 3˚C min⁻¹ and was held at 250˚C for 1 min, and from 250˚C - 300˚C with rate of 20˚C min⁻¹ and was held at 300˚C for 1 min. The injector and detector temperatures were set at 280˚C and 310˚C, respectively. Three μL volume of each sample was injected in the split less mode and the purge time was 1 min. To control the analytical reliability and assure recovery efficiency and accuracy of the results, four analyses were conducted on organochlorine compounds reference material SRM-2974 a freeze-dried muscle tissue (Mytilus edulis) provided by EIMP-IAEA. The laboratory results showed that recovery efficiency ranged from 90% to 105% with coefficients of variation of 8% - 15% for all organochlorine compounds. The limit of detection in the present study was estimated to be 0.014 ng・g^?1 for PCB and 0.014 ng・g^?1 for pesticides based on the minimum quantity of sample required for a discernible peak appeared on the chromatogram.

Muscles of fish showed the presence of a wide variety of organochlorines including α, β and γ-HCH, dieldrin, aldrin, endrin, DDT and their metabolites as well as PCBs (Table 1 and Table 2). The mean composition of OCPs in Sparus auratus was 17.96%, 6.46%, 75.54% for HCHs, TCs and DDTs, respectively. DDTs composition was much higher than HCHs and TCs, which might be attributed to the more bio-accumulative ability of DDTs (Table 1). Low concentrations of HCHs, which were recorded in fish tissues of the present study, reflect their lower potential for bioaccumulation than other pesticides. Furthermore, higher vapour pressures of HCHs facilitate relatively rapid atmospheric dissipation in the tropics, leaving fewer residues in soil and water [28] . The most striking difference in HCHs composition of the investigated Sparus auratus (approximately 18.30% of α-HCH, 70.48% of β-HCH and 11.23% of γ-HCH) is the high level of β-HCH was the predominant isomer of HCHs which can exist in the environment for several years because they are stable, resistant to microbial degradation, and have a long half-life with a low solubility and vapour pressure [29] . Although, aldrin is readily converted to dieldrin in many environmental compartments, the mean composition of Aldrin, Dieldrin and Endrin in Sparus auratus of the present study was 13.87%, 19.08% and 67.05%, respectively. This indicates that there is a weathered source of Aldrin with sufficient oxygen available for the oxidation process to its epoxide form; Dieldrin. Endrin is highly