ACKMAN ET AL.: FATTY ACIDS IN ATLANTIC STURGEON 



marine sturgeon, migrating into freshwater to 

 spawn, live off fat reserves (Scott and Grossman 

 1973). 



The subject of freshwater versus marine fatty 

 acid composition for fish oils and fats has been 

 discussed by various authors (Ackman 1967; 

 Farkas 1971; Ikekawa et al. 1972; Reichwald and 

 Meizies 1973), but not always from the same 

 viewpoint. There is, however, clear agreement 

 that in the depot fats of the sturgeon, from either 

 the freshwater or marine milieu, 18:2<o6 (linoleic 

 acid) is a minor (^1-2%) component and 20:4a)6 

 (arachidonic acid) is also of limited significance. 

 The low level of 18:2 <i)6 is probably a "marine" fat 

 characteristic as most freshwater fish have fats 

 with 5% or more of this acid (Ackman 1967; Farkas 

 and Herodek 1967; Mangold 1973; Reichwald and 

 Meizies 1973). In some other animals such as the 

 turtles, freshwater species freely deposit 18:24*6 

 and marine forms do not (Ackman, Hooper, and 

 Frair 1971). Unfortunately, many reports on the 

 composition of freshwater fish fats are confused 

 by fatty acid depositions from rearing on artificial 

 diets exceptionally rich in 18:2<i)6 and the normal 

 species pattern may be masked by this factor 

 (Albrecht and Breitsprecher 1969). The higher 

 polyunsaturated acids in depot fats of all stur- 

 geons studied to date are dominated by the Cgoand 

 C22 polyunsaturated fatty acids of the "<i)3" 

 (linolenic) family, in all analyses. The figures for 

 total C2oand C22 polyunsaturated acids in Atlantic 

 sturgeon A correspond fairly closely to those for 

 the marine A. sturio examined by Lovern (1932). 

 The tissues sampled by various authors are not 

 always clearly comparable. The "pink calf-like" 

 tissue (3.3% fat) of the sturgeon examined by 

 Reichwald and Meizies (1973) occurs dorsally above 

 the abdominal cavity and is also the main caudal 

 tissue, with the "white lard-like" tissue (52.9% fat) 

 interposed in an arrowhead fashion when viewed 

 in longitudinal section (I. Reichwald, pers. com- 

 mun.). The location of a transverse section could 

 show quite different relative locations for either 

 tissue. From the fat contents, it appears that our 

 "orange" layer corresponds to the "white" layer of 

 an European sturgeon (Reichwald and Meizies 

 1973) and possibly to the ventral layer of a 

 Japanese sturgeon (Shimma and Shimma 1968), 

 and our "muscle" corresponds to the "pink" tissue 

 of the former. Among differences in fatty acids of 

 interest listed for different animals may be men- 

 tioned 20:5(1)3 = V2 22:6*83 for two animals kept in 

 captivity on a marine fish diet (Shimma and 



Shimma 1968, see Table 3) and the virtual absence 

 of 20:5a»3 in the fat of the "white" tissue described 

 by Reichwald and Meizies (1973), although in the 

 "pink" tissue 20:5ft)3 >22:6a)3 agrees with our data, 

 as also reported in less comprehensive studies of 

 European sturgeon (Mangold 1973; Meizies and 

 Reichwald 1973). The depot fats of the marine 

 sturgeon we have investigated had 22:6«3 at about 

 half the level of 20:5 0)3, and we interpret the 

 analysis of the marine A. sturio by Lovern (1932) 

 to agree with our data. It appears that at some 

 point in the animals' spawning migration the 

 proportions of these two fatty acids could reverse. 

 Interestingly enough, only one out of four fresh- 

 water fish oils (from maria or Lota lota) examined 

 earlier contained larger proportions of 22:6«*3 than 

 of 20:5a)3 (Ackman 1967). 



The spawning period for Canadian Atlantic 

 sturgeon is presumably in early summer. The two 

 male fish examined showed no gonad development 

 and, therefore, if mature presumably they had 

 spawned and returned to the ocean. Oleic acid 

 (218:1) at 44-49% and palmitic acid (16:0) at 21-23% 

 are indicated by Reichwald and Meizies (1973) and 

 other studies (see above) to be the major com- 

 ponents of freshwater sturgeon fats. The depot 

 fats of the two marine Atlantic sturgeon we have 

 investigated differ in that both 18:1 totals are 20- 

 30% (magnitude inversely related to iodine value) 

 and 16:0 is about 15%. The original marine A. 

 sturio had about 36% 18:1 and 16-19% 16:0, or in 

 other words, the fats examined by Lovern (1932) 

 displayed a composition for these two fatty acids 

 intermediate to two more recent studies. 



The very different iodine values for sturgeon A 

 and B are accounted for mainly by the differences 

 in percentages of 20:5«)3, 22:5w3, and 22:6»3 in lieu 

 of 18:1 and other monoethylenic acids, as total sa- 

 turated acids are in the same proportion of fat in 

 both fish and the proportions of most minor unsa- 

 turated acids are not important enough to matter. 

 The monoethylenic fatty acids of fish B (total 

 about 45%) probably are more normal as judged by 

 the various low iodine values in the literature for 

 sturgeon fat. The resolving power of open-tubular 

 gas-liquid chromatograph for methyl esters of 

 monoethylenic fatty acids extends our knowledge 

 of the fatty acid biochemistry of the two Atlantic 

 sturgeon in this study. Virtually no 18:lo)ll, which 

 could only come from 20:l«i>ll, was observed. This 

 indicates that the fish were depositing fat and not 

 catabolizing it. On the other hand, the percentage 

 of 20:1<d7 was about the same as that of 20:l<i)9 in 



843 



