Short communicationTotal lipid content and fatty acid composition were determined for wild and cultivated gilthead seabream and sea bass. Fatty acid analyses were carried out by gas chromatography-mass spectrometry. Respective total lipid content of flesh in cultivated gilthead seabream and sea bass were 1.7-5.0-times those of wild samples. Palmitic acid (C16:0) and oleic acid (C18:1n-9) were the major fatty acids respectively among the saturated fatty acids and monounsaturated fatty acids of each fish species. It is noteworthy that both linoleic acid (C18:2n-6) and arachidonic acid (C20:4n-6) were predominant in total n-6 polyunsaturated fatty acids in the respective cultivated and wild types. Eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) amounts were significantly higher in flesh of cultivated fish than in wild fish.

Petroleum hydrocarbons are important pollutants of sea and marine organisms. The origin of hydrocarbons are either biogenic (endogenic) which are synthetised by marine organisms or exogenic due to oil pollution accumulated by marine organisms. The hydrocarbons found in algae were biogenic (Clarck and Blumer 1967;Youngblood et al.1971; Rossi et al. 1978;Youngblood and Blumer 1973) or exogenic (George 1961;Farrington and Tripp 1977; Miranov et al. 1981;Knutzen and Sortland 1982;Peckol et al. 1990). Some characteristics used to distinguish the origin of hydrocarbons in the marine ecosystem were the ratios of pristane (Pr)/phytane (Ph), C 17/Pr, C18/Ph and CPI (Carbon Preferences Index) values (Clarck and Finley 1974;Gearing et al. 1976;Farrington and Tripp 1977) and also the existence of alkenes and aromatic compounds.In this work oil pollution was investigated on the surface and inside of algae MATERIALS AND METHODSThe algae were collected from the northern and southern ends of the Bosphorus. The sampling sites are shown in Fig. 1. The algae collected from April-Dec. 1995 were green; Ulva lactuca L, Enteromorpha linza J. Agard, brown; Cystoseira barbata J. Agard, red; Ceramium rubrum (Huds.) J. Agard, Pterocladia capillacea (Grev.)Thuret et Bornet.Determination of oil pollution on the surface of the algae: 100 g wet weight alga was rinsed a few second with 3x50 ml dichloromethane (DCM), then filtrated through a filter paper. The algal residue was separated (a) and filtrate was dryed over anhydrous sodium sulphate then distilled under vacuum. The residue was taken with hexane and the volume adjusted to 10 ml and analysed by UV spectrofluorometry (UVF) and GCMS.Determination of oil inside of algae: the algae residue as described above (a), was dried in the open air and milled, extracted with DCM in Soxhlet for 4 h. The extract was distilled under vacuum. The residue was saponified with 0.5 % KOH in methanol for 1 h, 50 ml distilled water added and transferred to a separatory funnel, shaken with 50 ml pentane. The organic phase was separated and dried over anhydrous sodium sulphate and distilled under vacuum. The residue was taken with hexane, adjusted to 10 ml and analysed by UVF and GC/MS.

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The total lipid content and fatty acid composition were determined in the flesh and skin of wild and cultured rainbow trout in Turkey. The effect of diet content was also investigated on cultured trout. Gas chromatography-mass spectrometry (GC-MS) was used for fatty acid analyses. Total lipid content of skin was higher than flesh in both types and when compared appreciably higher in cultured fish. The predominant fatty acid was palmitic acid (C16:0) in saturated fatty acids and oleic acid (C18:1n-9) in monounsaturated fatty acids. The amount of eicosapentaenoic acid was double in wild and docosahexaenoic acid (DHA) 1.5 times higher in cultured fish flesh. The n-3/n-6 ratio was higher in cultured fish than wild fish. The levels of palmitic, oleic, linoleic (C18:2n-6) and palmitoleic (C16:1n-7) acids were high in skin. The level of EPA was the same in skin of wild fish but 5.5 times higher in cultured fish, whereas the proportion of DHA in skin was lower for wild and 3.5 times higher in cultured fish. Wild fish had a high level of linoleic, arachidonic (C20:4n-6) and linolenic (C18:3n-3) acids. The total amount of n-3 and n-6 polyunsaturated fatty acids was higher in flesh of wild fish than cultured fish, contrary to skin of cultured fish. The data obtained demonstrated that fatty acid composition of cultured fish did not depend on that of feed.KEY WORDS: cultured fish, fatty acid composition, n-3 fatty acids, rainbow trout, wild fish.