DIFFERENTIATION OF FRESHWATER CHARACTERISTICS OF 



FATTY ACIDS IN MARINE SPECIMENS OF 



THE ATLANTIC STURGEON, ACIPENSER OXYRHYNCHUS 



R. G. AcKMAN, C. A. Eaton, and B. A. Linke' 



ABSTRACT 



Lipids and fatty acids of two marine-caught specimens of the Atlantic sturgeon, Acipenser 

 oxyrhynchus, which spawns and also feeds in freshwater, were examined. Specific fat contents, re- 

 spectively 47.2 and 25.0% in orange-colored dorsal tissue and 8.5% in both livers, were high but not 

 unexpected for sturgeons generally. In each fish a very consistent basic fatty acid composition of depot 

 fats showed that this fat in various parts of the body had a common function. Depot fat from the fatter 

 fish had high iodine values (ca. 190) while in the leaner fish values were lower (ca. 135) and more typical 

 of sturgeons generally. The fatty acid details of depot fats showed some characteristics of marine fats, 

 such as the presence of the unusual wl and tr)4 polyunsaturated fatty acids, the low figure for linoleic 

 acid and relatively high proportions of long chain polyunsaturated fatty acids, but were more typical of 

 freshwater fats in the virtual absence of eicosenoic and docosenoic acids. Broadly speaking, the fatty 

 acids of the Atlantic sturgeon seem to place it in a special class of fish with fats generally resembling 

 freshwater fish fats in composition, despite its marine origin. 



The Atlantic sturgeon, Acipenser oxyrhynchus 

 Mitchill, is widely distributed along the Atlantic 

 coast of North America and is to be distinguished 

 from A. sturio, the common sea sturgeon of 

 Europe (Scott and Grossman 1973). The Atlantic 

 sturgeon is an anadromous fish, spawning in 

 freshwater,- whereas some other sturgeon species, 

 such as the lake sturgeon, A. fulvescens, are re- 

 stricted to freshwater. The most recent and de- 

 tailed study of sturgeon lipids and fatty acids has 

 been based on an A. sturio specimen, apparently 

 of freshwater origin, as it showed a fatty acid 

 pattern which is characteristic of lipids in fresh- 

 water fish (Reichwald and Meizies 1973). 



The standard reference book on fatty acids 

 states that sturgeon fats are "of the freshwater 

 type" (Hilditch and Williams 1964) although this 

 view was based on a single analysis of a specimen 

 of A. sturio caught in the North Sea (Lovern 1932). 

 We wish to report that a study of two saltwater A. 

 oxyrhynchus shows that, during its marine period, 

 the Atlantic sturgeon deposits fat with some 

 composition details corresponding to marine fatty 

 acid characteristics. However the fat definitely 



'Environment Canada, Fisheries and Marine Service, Halifax 

 Laboratory, P.O. Box 429, Halifax, Nova Scotia B3J 2R3 Can. 



^Sturgeon were once so common that those blocked by the falls 

 in the Hudson river were taken in large quantities and marketed 

 in New York City as "Albany veal." They appear to be returning 

 to their former habitat in large numbers (R. Severo, New York 

 Times, 9 July 1975). 



lacks other details characteristic of fats of higher 

 marine organisms and thus reinforces the 

 published viewpoint based on the common sea 

 sturgeon of the Northeast Atlantic. 



MATERIALS AND METHODS 



Samples 



Two A. oxyrhynchus were acquired from fish 

 traps located in an area of the entrance to Halifax 

 Harbour known as Eastern Passage. Both were 

 male, that taken on 12 October 1968 (A) being 150 

 cm in length and that taken 30 August 1973 (B) 

 being 155 cm. Fish A was frozen whole at -40°C 

 until dissected in March 1969. Fish B was held 

 overnight in an aquarium and dissected immedi- 

 ately after sacrifice. In both cases sections were cut 

 transversely through the middle of the fish. In fish 

 A this was done while frozen and the cut section 

 included liver which was recovered for study, while 

 in fish B the liver was removed separately from the 

 fish. Both fish showed a soft fatty orange layer 

 between the dorsal skin and muscle, of one or more 

 centimeters in thickness, but thinning down the 

 flanks. Parts of this layer penetrated the muscle, 

 especially between myotomes, and streaks of 

 similar colored material appeared in the muscle. A 

 section through fish B was observed to have a 



Manuscript accepted January 1975. 

 FISHERY BULLETIN: VOL. 73, NO. 4, 1975. 



838 



