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The fat and fatty acid compositions of 28 species of fish and invertebrates (n = 954) from the Scotian Shelf, Georges Bank, and the Gulf of St. Lawrence were determined. Discriminant analysis of the 16 most numerous species (n [Formula: see text] 18 each), using 17 major fatty acids, classified species with greater than 98% accuracy and grouped species into three general clusters (gadids, flatfish, and planktivores) with similar fatty acid compositions, and likely, similar diets. A number of species exhibited changes in fatty acid signatures with increasing size (multivariate analysis of variance), which corresponded with known dietary shifts reported from stomach contents analyses. Location effects were also observed among the three major geographical regions and were probably due to broad-scale variations in prey assemblages and phytoplankton composition in the northwestern Atlantic. Despite these effects, within-species variation was still substantially less than among-species variation. Thus, fatty acid signatures can be used to distinguish and characterize fish and invertebrate species in a given ecosystem, as well as to study finer-scale trophic interactions of these species. These data also have applications at higher trophic levels and will serve as a prey database for studying the diets of other fish and marine mammal predators using fatty acid signatures.

Twelve species of marine unicellular algae have been cultured under comparable conditions and the total fatty acids determined b1' gas liquid chromatography. Some specific fatty acid relationships paralleling taxonornic groupings were detected but generally individual fatty acids within various algal classes shorved large relative variations. The four Bacillariophyceae examined were notable for fatty acid cornpositions giving iodine values (150, rvhereas in eight other classes the iodine values were all approximately 200. It is suggested that 5,8,11,14,17-eicosapentaenoic acid, found to be a common algal longer-chain polyunsaturated fatty acid, is characteristically deposited in the lipids of filter-feeders ingesting unicellular algae.

A gas chromatographic (GC) method using a capillary column for analysis of encapsulated fish oils and ethyl esters was studied collaboratively in 21 laboratories. Each collaborator analyzed 6 soft-gelatin encapsulated samples; 5 were trlacylglycerol oils (one was a blind duplicate), and one was an ethyl ester concentrate of omega-3 (n-3) polyunsaturates. Constituent fatty acids of the oils were converted to methyl esters by base-catalyzed transesterlflcatlon of the oils; any free acids in the oils were esterlfied by subsequent reaction with BF3/CH3OH. The ethyl ester concentrate required no further derlvatlzation. Results were reported as area percentages of 24 analytes of nutritional or biochemical interest. In addition, weights (mg/g sample) of EPA (all-c/s-5,8,11,14,17-elcosapentaenolc acid or 20:5n-3) and DHA (all-c/s- 4,7,10,13,16,19-docosahexaenoic acid or 22:6n-3) were determined through the use of the internal standards, respectively, methyl tricosanoate (23:0) and ethyl 23:0, for the methyl and ethyl esters. The only instrumentation specifically required was a flexible fused silica capillary GC column coated with a bonded polyglycol such as Carbowax-20M, an oxygen scrubber Installed In the carrier gas supply line, and a flame Ionization detector (FID). Most of the collaborators experienced little difficulty In applying the method, and, of 2526 values reported, only 4.3% were identified as outlier values. The reproducibility relative standard deviations (RSDR) compared favorably in most instances with, or were substantially better than, those of 2 earlier collaborative studies of fish oils. Because the variances were homogeneous, standard deviations and relative standard deviations determined on the area percent analyses of the blind duplicate oils were pooled to give the following mean values: sr = 0.15, RSDr = 4.88%, sR = 0.41, and RSDR = 12.91%. Analytes that rarely occur at greater than 0.5% In marine oils (22:0,22:4n-6,22:5n-6,24:0, and 24:1) were not Included in these calculations. The method was adopted first action by AOAC International as an American Oil Chemists' Society (AOCS)-AOAC method.