; Phone: 0039 02 50315759;Caviars are the salt-cured and preserved eggs of many sturgeon species that have been separated from the supporting connective tissue. The most famous and valuable caviars are produced from harvested sturgeons in the area of Caspian Sea, namely Beluga (Huso huso), Osetra (Acipenser gueldenstaedtii) and Sevruga caviar (Acipenser stellatus). Over the past few decades, owing to the strong demand for sturgeon caviar, the over-exploitation of natural stocks has led to a dramatic decreases of the supplies. To protect these endangered species, in 1997 the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) decided to limit trade of caviar by listing all sturgeon species on the Annex II of the convention.The lack of supply and the continuous demand for this product have increased the feasibility of caviar production from aquaculture. There are high quality and environmentally friendly alternatives available such as caviar produced from farmed white sturgeon (Acipenser transmontanus) in Italy, Siberian sturgeon (Acipenser baerii) in France and Germany, Adriatic sturgeon (Acipenser naccarii) in Italy and Spain. Among pure species, Acipenser stellatus, the beluga and the paddlefish (Polyodon spathula) are reared mainly in extensive or semi-intensive farming on a limited scale. The successful of producing caviar from farmed sturgeon has arisen several investigations aiming to produce the chemical characterization of the product. Biochemical assays together with sensory studies have been carried out with the purpose to determine whether compositional and sensory differences might be observed between caviar from farmed and wild sturgeon.The study was designed to characterize caviar from farmed white sturgeons (Acipenser transmontanus) subjected to different dietary treatments before eggs collection. Fifty caviar samples from fifty farmed sturgeons have been analyzed for proximate composition, fatty acid and volatile compounds.

In this study, the proximate and fatty acid compositions of the muscle tissue of 186 samples of fish belonging to fifteen species of freshwater fish harvested in subalpine lakes (bleak, shad, crucian carp, whitefish, common carp, pike, black bullhead, burbot, perch, Italian roach, roach, rudd, wels catfish, chub and tench) were investigated. Most of the fish demonstrated a lipid content in the fillet lower than 2.0 g 100 g(-1) wet weight (range 0.6-9.7). A strong relationship between feeding behavior and fatty acid composition of the muscle lipids was observed. Planktivorous fish showed the lowest amounts of n-3 fatty acids (p < 0.05), but the highest monounsaturated fatty acid (MUFA) contents, in particular 18:1n-9. Conversely, carnivorous fish showed the highest amounts of saturated fatty acids and n-3 fatty acids (p < 0.05), but the lowest MUFA contents. Omnivorous fish showed substantial proportions of n-3 fatty acids and the highest contents of n-6 fatty acids. Principal component analysis showed a distinct separation between fish species according to their feeding habits and demonstrated that the most contributing trophic markers were 18:1n-9, 18:3n-3, 22:6n-3 and 20:4n-6. The quantitative amounts n-3 polyunsaturated fatty acid in muscle tissues varied depending on the fish species, the lipid content and the feeding habits. Some species were very lean, and therefore would be poor choices for human consumption to meet dietary n-3 fatty acid requirements. Nevertheless, the more frequently consumed and appreciated fish, shad and whitefish, had EPA and DHA contents in the range 900-1,000 mg 100 g(-1) fresh fillet.

Fatty acid composition and stable isotope ratios of carbon (delta(13)C) and nitrogen (delta(15)N) were determined in muscle tissue of turbot (Psetta maxima). The multivariate analysis of the data was performed to evaluate their utility in discriminating wild and farmed fish. Wild (n=30) and farmed (n=30) turbot of different geographical origins (Denmark, The Netherlands, and Spain) were sampled from March 2006 to February 2007. The application of linear discriminant analysis (LDA) and soft independent modeling of class analogy (SIMCA) to analytical data demonstrated the combination of fatty acids and isotopic measurements to be a promising method to discriminate between wild and farmed fish and between wild fish of different geographical origin. In particular, IRMS (Isotope Ratio Mass Spectrometry) alone did not permit us to separate completely farmed from wild samples, resulting in some overlaps between Danish wild and Spanish farmed turbot. On the other hand, fatty acids alone differentiated between farmed and wild samples by 18:2n-6 but were not able to distinguish between the two groups of wild turbot. When applying LDA isotope ratios, 18:2n-6, 18:3n-3, and 20:4n-6 fatty acids were decisive to distinguish farmed from wild turbot of different geographical origin, while delta(15)N, 18:2n-6, and 20:1n-11 were chosen to classify wild samples from different fishing zones. In both cases, 18:2n-6 and delta(15)N were determinant for classification purposes. We would like to emphasize that IRMS produces rapid results and could be the most promising technique to distinguish wild fish of different origin. Similarly, fatty acid composition could be used to easily distinguish farmed from wild samples.

Monola oil, a high oleic acid canola cultivar, and canola oil were evaluated as replacers of fish oil at three levels of inclusion (60%, 75% and 90%) in rainbow trout diets. After a 27-week grow-out cycle, the diet-induced effects on growth, fatty acid metabolism and final eating quality were assessed. Overall, no effects were noted for growth, feed utilisation or fish biometry, and the fatty acid composition of fish fillets mirrored that of the diets. Dietary treatments affected fillet lipid oxidation (free malondialdehyde), pigmentation and flavour volatile compounds, but only minor effects on sensorial attributes were detected. Ultimately, both oils were demonstrated to possess, to differing extents, suitable qualities to adequately replace fish oil from the perspective of fish performance and final product quality. However, further research is required to alleviate on-going issues associated with the loss of health promoting attributes (n-3 long chain polyunsaturated fatty acids) of final farmed products.