C S I R O P U B L I S H I N G

Volume 49, 1998© CSIRO 1998

A journal for the publication of original contributions in physical oceanography, marine chemistry, marine and estuarine biology and limnology

w w w. p u b l i s h . c s i ro . a u / j o u r n a l s / m f r

All enquiries and manuscripts should be directed to Marine and Freshwater ResearchCSIRO PUBLISHINGPO Box 1139 (150 Oxford St)Collingwood Telephone: 61 3 9662 7618Vic. 3066 Facsimile: 61 3 9662 7611Australia Email: ann.grant@publish.csiro.au

Published by CSIRO PUBLISHINGfor CSIRO and the

Australian Academy of Science

&MarineFreshwaterResearch

Introduction

The main sources of oils containing eicosapentaenoicacid [EPA, 20:5(n-3)] and docosahexaenoic acid [DHA,22:6(n-3)] globally have included pilchard, sardine,menhaden, cod, jack mackerel and tuna. In Australia themain sources are jack mackerel and tuna. Decreased catchesare threatening the long-term availability of various speciesas sources of oil. Consequently, it is desirable to identifynew sources of oils rich in EPA and DHA that are readilyavailable.

The southern Australian shark fishery has an annualproduction of about 5000 t and is worth >$A20 million tothe fishermen (or >$A50 million, retail value) (Campbell etal. 1992; Last and Stevens 1994). The fillets, in someregions of Australia referred to as ‘flake’, are marketed forhuman consumption and mainly are taken from gummysharks (Mustelus antarcticus Günther 1870) and schoolsharks (Galeorhinus galeus Linnaeus 1758). Dalatias licha(black shark) and other species such as Squalus acanthias(white-spotted spurdog ) also are occasionally used. Theproduction of fillets usually results in a large quantity of by-product, which currently has little commercial value. Use ofby-products has been successful in Australia for other sharkspecies (e.g. deep-sea dogfish as a source of purifiedsqualene and diacylglyceryl ethers) (P. Nichols et al. 1994,1997; Bakes and Nichols 1995).

The sharks in the fishery are generally between 0.8 and1.6 m in length and weigh between 2 and 25 kg (J. Stevens,personal communication). The by-product generated by this

fishery is in excess of 2000 t per year and includes skin,guts, head and liver, representing 45–50% of the total bodyweight. The liver of these sharks usually accounts for 10%of the total body weight and, on the basis of a 50% yield ofoil from the liver, the fishery would yield ~200–250 t of liveroil per year from the present catches.

The w-3 polyunsaturated fatty acids (PUFAs), EPA andDHA, are beneficial against various disorders (Kinsella1986, 1987). For example, they may reduce the incidence ofcoronary heart disease (McLennan et al. 1988; Connor1997); consumption of fish two or three times per weekappears to result in measurable benefits in this respect(Siscovick et al. 1995). Similarly, w-3 PUFAs may play arole in the treatment of inflammatory diseases such asarthritis (Cleland and James 1997) and in infant nutrition(Carson 1995; Heird et al. 1997). The biochemical effects offish-derived and plant lipids in cancer therapy also havebeen examined (e.g. Burns and Spector 1994; Horrobin1997), although further research is required; in cancertherapy, PUFAs are seen as an adjunct to chemotherapyrather than as a dietary supplement alone. w-3 PUFAs areused also in aquaculture feeds because these components areessential for survival, growth and development in manyspecies (Langdon and Waldock 1981; Kanazawa 1985; D. Nichols et al. 1996).

The literature available on the lipids and fatty acids of M.antarcticus and G. galeus is restricted to one study (Craig1978) that presents lipid composition data. We present thelipid content and composition and the fatty acid profiles of

Mar. Freshwater Res., 1998, 49, 763–767

10.1071/MF97241 1323-1650/98/070763

Oils rich in docosahexaenoic acid in livers of sharks from temperate Australian waters

Peter D. Nichols, Michael J. Bakes and Nicholas G. Elliott

CSIRO Division of Marine Research, GPO Box 1538, Hobart, Tas. 7001, Australia. email:Peter.Nichols@marine.csiro.au

Abstract. The livers from the two main commercially-targeted shark species in southern Australia(Mustelus antarcticus, gummy shark; Galeorhinus galeus, school shark), together with Squalusacanthias (white-spotted spurdog), were analysed for oil content and composition, and fatty acidcomposition. The yield of oil from the liver was 30-64% (wet weight) for M. antarcticus and 50-53%(wet weight) for G. galeus. Lipid classes were determined by thin-layer chromatography with flameionization detection, with the major lipid being triacylglycerol (³95%); other minor lipids were polarlipid, wax ester, sterol (mainly cholesterol) and free fatty acid. Long-chain w-3 polyunsaturated fattyacids accounted for between 33% and 39% of the total fatty acids in all three species, anddocosahexaenoic acid (DHA) concentrations were between 13% and 18%. The liver oils of M.antarcticus and G. galeus and other shark species may be an attractive source of w-3 fatty acids,specifically DHA, for direct use and/or for adding further value.

Extra keywords: Mustelus antarcticus, Galeorhinus galeus, Squalus acanthias, lipids, triacylglycerol,fatty acids, polyunsaturated fatty acids.

© CSIRO 1998

Peter D. Nichols et al.764

the liver oils from M. antarcticus and G. galeus, and fromSqualus acanthias.

Materials and methodsSample collection

Three specimens of M. antarcticus and three of G. galeus were collectedfor their livers. M. antarcticus specimens were from South Australian (No.288, total length (TL) 1020 mm, and No. 285, 1200 mm; January 1994) andNew South Wales (No. 165, TL 580 mm; June 1993) waters, were allfemale and were caught at ~90 m depth. For G. galeus, two specimens (No.127, TL 805 mm, and No. 128, 560 mm; June 1994) were from Tasmanianwaters and the other (No. 27, TL 960 mm; February 1994) from NewZealand, and all were female (reproductive status not known); their depthdata were not available. All shark specimens were obtained fromcommercial catches and were stored at –20°C while in transit and then at–80°C in the laboratory.

An oil processor in Tasmania supplied samples of liver oil from school,gummy and white-spotted spurdog sharks. These oils had been obtained bymechanical maceration of the livers followed by heating at 50–60°C thenseparation for 2–4 days and decantation of the oil.

Lipid extraction

Aliquots of liver (1–3 g) were homogenized in a pre-rinsed mortar andpestle and were quantitatively transferred to a separating funnel usingchloroform, methanol and water (ratio 1:2:0.8 v/v/v) (Bligh and Dyer1959). Samples were mixed and left to extract overnight. Phases wereseparated by addition of chloroform and water so that the final ratio ofsolvents was 1:1:0.9 v/v/v. Following isolation and concentration of thelower chloroform layer, samples were transferred to vials and the excesssolvent was removed under nitrogen prior to determining the oil content ofthe liver.

Lipid analyses

A subsample of the oil (obtained either by extraction or as the crudeproduct) was diluted and analysed for lipid classes in an Iatroscan MK VTLC-FID analyser (Iatron Laboratories, Japan). Two solvent systems wereused to identify lipids: hexane/diethyl ether/acetic acid (60:17:0.2 v/v/v)and hexane/diethyl ether (96:4) provided resolution between most commonlipid classes (Volkman and Nichols 1991) and reproducibility was ± 5%(unpublished data). Data were acquired with the aid of DAPA software(Kalamunda, Australia).

FAME analyses

An aliquot of the total lipid extract was methylated under nitrogen byusing a solution of methanol, chloroform and hydrochloric acid (10:1:1v/v/v) and the fatty acid methyl esters (FAMEs) were extracted withhexane: chloroform (4:1 v/v). FAMEs were then concentrated undernitrogen and treated with N,O-bis-(trimethylsilyl) trifluoroacetamide toconvert free hydroxyl groups to their corresponding trimethyl silyl ethers.Samples were then blown to dryness under nitrogen and made up to aknown volume in chloroform containing methyl tricosanoate (internal-injection standard). FAMEs were analysed with a HP 5890A gaschromatograph fitted with a split/splitless injector and a HP 7673autosampler, a FID and a HP-1 cross-linked methyl silicone fused silicacapillary column (50 m ´ 0.32 mm i.d.). Hydrogen was the carrier gas. Theoven temperature was held at 50°C for 1 min before being raised to 150°Cby 30°C min–1, then to 250°C by 2°C min–1 and finally to 300°C by 5°Cmin–1. Peaks were quantified with DAPA chromatography software.Individual components were identified by comparing retention times andmass spectral data (Fisons MD-800 system configured as above) with dataobtained for authentic and laboratory standards.

Vitamin A and E analyses

Representative aliquots of the oils were sent to the AustralianGovernment Analytical Laboratories, South Australia, for vitamin assay.Standard analytical techniques were used for determination of vitamins Aand E (Brubacker et al. 1985; De Leenheer et al. 1985).

Results and discussion

Oil composition

The lipid content and composition of the liver oils fromthe gummy and school sharks (Table 1) was similar, withboth sharks containing 95–99% triacylglycerol. The oils alsocontained low concentrations of polar lipid (1–4%), waxester (trace to 2%) and sterol (identified by gaschromatography as cholesterol; trace to 1%). Commerciallyproduced oil for the two species was similar in composition(Table 1). Only trace levels (less than 0.2% of the total lipid)of free fatty acids were detected in two of the eight samplesanalysed (Table 1). It is common for fish-derived oilsproduced by industry to contain elevated concentrations of

Table 1. Lipid class composition and vitamin content of selected liver oils isolated from school sharks and gummy sharksF, female; WE, wax ester; TAG, triacylglycerol; FFA, free fatty acid; ST, sterol; PL, polar lipid. tr, < 1%; nd, not determined; –, not detected.

Commercial refers to the bulk oil produced by Tasmanian processors

Sample Sex/locality Percentage composition Oil recovery Retinol (A) a-tocopherol (E)WE TAG FFA ST PL from liver (%) (mg/100g of oil) (mg/100g of oil)

Gummy sharkGS165 F/NSW tr 95 tr 0 4 30 GS285 F/SA 2 97 – tr 1 64GS288 F/SA 0 96 – tr 3 47 Commercial nd/Tas. 3 97 – tr tr nd 6.9 18.0School sharkSch27 F/NZ tr 98 – tr 2 50 Sch127 F/Tas. tr 99 – tr 0 52Sch128 F/Tas. 2 96 tr tr 2 53 Commercial nd/Tas. 3 97 – tr tr nd 14.0 8.3

765

free fatty acid (up to 5% free fatty acid; Nichols, Bakes,Elliott, unpublished data). This is due in part to poor storage,handling and/or processing conditions.

Triacylglycerols generally are the preferred form forstorage and delivery of PUFAs in health and pharmaceuticalproducts because of their thermal and oxidative stability.The high concentrations of triacylglycerol in the liver oils ofthe species examined in this study is an attractive feature forthese oils that may allow rapid and efficient processingcompared with oils derived from other species. In contrast,other oils currently available in Australia (e.g. from salmonand tuna) may contain high concentrations of polar lipid,free fatty acid, cholesterol and other unwanted compounds(Nichols, unpublished).

Gummy shark livers showed the greatest variation in lipidcontent, with concentrations ranging between 30% and 64%lipid (wet mass basis). The lipid content of the school sharklivers was considerably less variable (50–53%). Thevariation in liver oil content observed for gummy shark maybe due to a range of factors including season, size, foodavailability and composition, and location.

Compared with livers from deep-sea sharks, the yield ofoil from the liver of the temperate, mid-water speciesanalysed in this study is low (50% oil in livers from schooland gummy sharks compared with 80% oil in livers fromdeep-sea sharks). However, the proportion of the desiredcomponent (99% triacylglycerol v. 40–85% squalenerespectively) is much greater. Deep-sea sharks are largelycaught as a by-catch in Australia and the livers from thesedeep-sea species yield the isoprenoid hydrocarbon squalene,a high-boiling-point liquid used in lubricants, cosmetics andnutritional products. Triacylglycerols are mainly used as astable form of lipid to provide long-chain PUFAs to humansand/or in aquaculture feeds. Comparable yields of oilsuggest that it could be economically feasible to extract theoil from the gummy and school sharks. For example, a deep-sea shark liver contains 80% oil, with 40–85% (mean ~60%)of the oil being squalene; the liver would contain 48%squalene (mass basis). For the gummy and school sharks(liver contains approximately 50% oil), the triacylglycerol-containing liver oil would be also ~48% (mass basis)suggesting that it may be feasible to exploit these oils.

Vitamins

Vitamin A (retinol) was assayed at 6.9 and 14 mg per100g (of oil), and vitamin E (a-tocopherol) was assayed to be18 and 8.3 mg per 100 g (of oil) in gummy and school sharksrespectively (Table 1). Literature available on the vitamincontent and composition of these Australian species islimited. However, the vitamin concentrations recorded forgummy and school sharks are low compared with those inother species from which vitamins are obtained. Forexample, the white-spotted spurdog contained 25 mgvitamin E per 100 g of oil (Sunarya et al. 1996).

Fatty acid composition

The major fatty acids in liver oil of both gummy andschool sharks included 16:0, 22:6(n-3), 18:1(n-9)c and20:5(n-3), and minor components were 16:1(n-7)c, 20:4(n-6), 18:0 and 18:1(n-7)c (Tables 2 and 3). EPA accounted for6–14% of the total fatty acid in gummy sharks and 8–11% inschool sharks. DHA was present at higher concentrations inboth species (13–18% total fatty acid in gummy sharks and14–19% in school sharks). Within-species variation was lessapparent in the school sharks; gummy sharks showed, forexample, greater variation in the concentrations of EPA andDHA. Specimen GS165 contained higher concentrations ofEPA (14% v. 7% in the other specimens) and lowerconcentrations of DHA (13% v. 18% in the otherspecimens). This may be due to the difference ingeographical provenance and/or other factors, as notedabove for oil content.

White-spotted spurdog differed from gummy and schoolsharks in fatty acid composition of the liver oil. The oil fromthis species contained higher concentrations ofmonounsaturated fatty acids (50% of total fatty acids),comprising 18:1, 20:1 and 22:1, with 16:0 and DHA alsomajor components (Table 2). Concentration of total PUFAswas lower in the white-spotted spurdog than in the gummyand school sharks, with slightly lower concentrations of thetwo essential PUFAs observed (EPA 4%, DHA 11%; Tables2 and 3). This species currently supplements the flakemarket, and the quantities of liver available to processors offish by-product may not be as high as for gummy and schoolsharks. However, on the basis of the similar concentrationsof the two essential PUFAs, EPA and DHA, liver oil fromthe white-spotted spurdog may be blended with liver oilfrom gummy and school sharks for the preparation of healthproducts or feeds for PUFA enrichment.

Commercial considerations

The increased demand for oils rich in EPA and DHA hasled to an expansion of the biotechnology industry,particularly the mass culture of yeast, microalgae andbacteria. The microorganisms can be grown heterotro-phically to produce PUFA-containing oils; this feature isadvantageous when considering the long-term sustainabilityof some of the wild fisheries and palatability of fish oils.However, the cost of potential production of PUFA-containing oil from these various single-cell organisms isconsiderably higher than for the production of fish oils.Other issues with oils from single cells include potentialproduction of undesirable components including possibletoxic compounds and other unwanted lipid classes.

The present results suggest that the by-product generatedfrom existing Australian shark fisheries could be betterexploited with respect to potential sources of w-3 PUFA-containing oils. Fish oils currently used in Australia (e.g.MaxEPA) are largely imported and have an EPA:DHA ratio

PUFA-containing liver oils from Australian sharks

Peter D. Nichols et al.766

of approximately 1.5. In contrast the Australian oils, such asobserved in this study, show a ratio of EPA:DHA of less than1, typically ~0.6 or lower (Table 3, and unpublished data).Because of the potential neurodevelopmental benefits, theincreased interest in DHA-containing oils rather than oilswith EPA>DHA may see an increase in the potential forDHA-containing fish oils.

The concentrations of DHA found in gummy, school andwhite-spotted spurdog shark liver oils are as high as some ofthe oils currently marketed as sources of this fatty acid(Table 3). Although the oil from the gummy and schoolsharks is discarded through the disposal of the livers, theopportunity exists to better exploit the by-product from theshark and other fisheries. Even if the current catch levels of

Table 2. Fatty acid composition (%) of gummy shark and school shark liver oils (both commercial and extracted) and commercialoil from white-spotted spurdog liver

Values are for a single analysis and have previously been found to be reproducible to ± 5%. tr, trace (< 0.1%); nd, not determined

Fatty acid Percentage compositionGummy shark School shark White-spotted

GS165 GS285 GS88 Comm. Sch27 Sch127 Sch128 Comm. spurdog

14:0 1.6 2.8 2.4 2.1 3.1 3.2 2.5 3.8 3.415:0 0.8 0.7 1.0 0.5 0.6 0.7 0.8 0.5 0.616:0 18.5 20.0 20.6 18.2 16.7 19.1 17.9 14.7 16.317:0 1.7 1.5 1.7 0.9 0.6 0.9 1.0 0.5 –18:0 8.0 8.4 7.9 4.9 5.5 5.7 6.1 3.9 3.220:0 0.3 tr 0.2 0.1 tr 0.2 0.2 0.1 trSum Saturates 31.0 33.6 33.9 26.7 26.6 29.8 28.4 23.5 23.5

i15:0 0.2 tr 0.2 0.1 0.2 0.2 0.2 0.2 0.2a15:0 – tr tr tr tr tr tr tr tri16:0 0.2 tr 0.2 0.1 0.2 0.2 0.3 0.1 –br 17:1 0.3 0.4 0.7 0.4 0.3 0.4 0.6 0.3 0.5i17:0 0.8 0.5 0.8 0.5 0.5 0.6 0.6 0.3 0.3a17:0 1.0 0.9 1.0 0.9 0.7 1.1 1.0 0.6 0.6Sum Branched 2.5 2.0 2.9 2.0 1.8 2.4 2.7 1.5 1.6

14:1 – – – 0.1 – tr – 0.1 –16:1(n–9)c 0.3 0.5 0.5 0.5 0.3 0.5 0.3 0.3 0.216:1(n–7)c 4.7 4.7 4.3 6.6 4.8 6.9 5.2 4.5 3.716:1 0.3 0.3 0.2 0.1 0.2 0.4 0.2 0.2 0.216:1 0.2 tr 0.2 – 0.2 0.2 0.2 – –18:1(n–9)c 12.1 13.9 12.4 17.0 17.2 18.1 12.1 18.9 20.818:1(n–7)c 6.6 5.3 6.1 3.9 5.4 5.1 5.2 3.5 4.318:1(n–5)c 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.3 0.320:1 3.1 3.5 2.4 5.0 4.5 2.7 3.0 6.8 14.022:1 tr 0.4 tr 1.1 1.0 0.5 0.9 2.0 6.222:1 tr 0.4 tr 0.7 0.8 0.3 0.9 1.6 4.6Sum MUFA 27.9 28.9 26.5 34.5 33.9 34.7 27.6 36.6 49.7

C16 PUFA tr – tr 0.2 0.4 tr tr 0.5 0.218:2(n–6) 1.4 1.2 1.8 0.9 1.7 1.4 1.3 1.6 1.418:3(n–3) tr tr 0.3 0.3 0.4 0.4 0.2 0.2 0.418:4(n–3) 0.4 0.3 0.7 0.5 1.5 0.3 0.6 1.7 –18:3(n–6) tr tr tr – tr tr tr – 1.020:2(n–6) 1.3 0.9 1.0 – 0.4 0.4 0.4 – 0.320:3(n–6) 0.2 tr 0.2 – tr 0.2 0.3 – 0.120:4(n–3) 0.5 0.4 0.5 0.6 1.3 0.5 0.6 1.5 2.220:4(n–6) 4.0 4.6 3.4 3.3 1.3 4.0 3.3 – 0.420:5(n–3) 13.9 6.1 8.0 7.4 10.0 8.2 11.4 10.1 3.922:4(n–3) 0.3 0.3 0.3 0.4 0.3 0.3 0.4 0.3 –22:4(n–6) 0.9 1.3 0.9 0.9 0.3 1.0 1.0 0.3 0.422:5(n–3) 2.3 2.4 1.9 2.3 3.1 2.5 2.8 2.9 2.722:6(n–3) 13.2 17.7 17.7 16.5 16.8 13.6 18.8 16.5 11.3Sum PUFA 38.7 35.5 36.8 33.3 37.6 33.1 41.2 35.6 24.3Total 100.0 100.0 100.0 96.5 100.0 100.0 100.0 97.2 99.1Cholesterol (mg g–1) 0.3 0.1 0.3 nd 0.1 0.1 0.1 nd nd

767

gummy and school sharks are not sustained, the fishery islikely to continue in some form in southern Australia. Byenhancing conversion of the by-product material into value-added products, it may be possible to help maximizeeconomic yields to the fishery.

Acknowledgment

The authors acknowledge the contribution of JohnStevens and Terry Walker for biological and marketinformation, and Stephanie Davenport, Patti Virtue, PeterRothlisberg and three anonymous MFR referees forcomments on the manuscript. Fisheries Research andDevelopment Corporation (FRDC 94/115) funded this studyand the interest from Australian industry (Beku and Scales)is also acknowledged.

ReferencesBakes, M. J., and Nichols, P. D. (1995). Lipid, fatty acid and squalene

composition of liver oil from six species of deep sea sharks collected insouthern Australian waters. Comparative Biochemistry and Physiology110B, 267–75.

Bligh, E. G., and Dyer, W. J. (1959). A rapid method of total lipidextraction and purification. Canadian Journal of Biochemistry andPhysiology 37, 911–17.

Brubacker, G., Muller-Mulot, W., and Southgate, D. A. T. (1985).‘Methods for the Determination of Vitamins in Food.’ (Elsevier AppliedScience: London.)

Burns, C. P., and Spector, A. A. (1994). Biochemical effects of lipids oncancer therapy. Journal of Nutrition and Biochemistry 5, 114–23.

Campbell, D., Battaglene, T., and Pascoe, S. (1992). Management optionsfor the southern shark fishery. Australian Fisheries 51(2), 7–10.

Carson, S. E. (1995). The role of PUFA in infant nutrition. INFORM 6,940–6.

Cleland, L. G., and James, M. J. (1997). Rheumatoid arthritis and thebalance of dietary N-6 and N-3 essential fatty acids. British Journal ofRheumatology 36, 513–14.

Connor, W. E. (1997). The beneficial effects of omega-3 fatty acids:cardiovascular disease and neurodevelopment. Current Opinion inLipidology 8, 1–3.

Craig, J. C. A. (1978). The lipids of six species of shark. Journal of theMarine Biological Association of the United Kingdom 58, 913–21.

De Leenheer, A. P., Lambert, W. E., and De Ruyter, M. G. M. (1985).‘Modern Chromatographic Analysis of the Vitamins.’ (Marcel Dekker:New York.)

Heird, W. C., Prager, T. C., and Anderson, R. E. (1997).Docosahexaenoic acid and the development and function of the infantretina. Current Opinion in Lipidology 8, 12–16.

Horrobin, D. F. (1997). The medical uses of vegetable oils. In‘Proceedings, Pacific Oils 2000’. (Ed. C. J. O’Connor.) pp. 39–43.(Uniprint: Auckand, NZ.)

Kanazawa, A. (1985). Nutrition of penaeid prawns and shrimps. In‘Proceedings of the 1st International Conference on Culture of PenaeidPrawns/Shrimps’. (Eds Y. Taki et al.) pp. 123–30. (South-East AsianFisheries Development Centre: IIoilo.)

Kinsella, J. E. (1986). Food components with potential therapeuticbenefits: the n-3 polyunsaturated fatty acids of fish oils. FoodTechnology (Feb.), 89–97

Kinsella, J. E. (1987). ‘Seafoods and Fish Oils in Human Health andDisease.’ (Marcel Dekker: New York.) 317 pp.

Langdon, C. J., and Waldock, M. J. (1981). The effect of algal andartificial diets on the growth and fatty acid composition of Crassostreagigas spat. Journal of the Marine Biological Association of the UnitedKingdom 61, 431–48.

Last, P. R., and Stevens, J. D. (1994). ‘Sharks and Rays of Australia.’(CSIRO: Melbourne.) 513 pp.

McLennan, P. L., Abeywardena, M. Y., and Charnock, J. S. (1988).Dietary fish oil prevents ventricular fibrillation following coronaryartery occlusion and reperfusion. American Heart Journal 116, 709–17.

Nichols, D. S., Hart, P., Nichols, P. D., and McMeekin, T. A. (1996).Enrichment of the rotifer Brachionus plicatilis fed on Antarcticbacterium containing polyunsaturated fatty acids. Aquaculture 147,115–25.

Nichols, P. D., Nichols, D. S., and Bakes, M. J. (1994). Recentdevelopments in marine oil products in Australia. INFORM 5, 254–61.

Nichols, P., Bakes, M., Mooney, B., Elliott, N., and Strauss, C. (1997).Developments with marine oil products in Australia. In ‘Proceedings,Pacific Oils 2000’. (Ed. C. J. O’Connor.) pp. 111–14. (Uniprint:Auckand, NZ.)

Siscovick, D. S., Raghunathan, T. E., King, I., Weinmann, S., Wicklund,K. G., Albright, J., Bovbjerg, V., Arbogast, P., Smith, H., Kushi, L., Cobb, L. A., Copass, M. K., Psaty, B. M., Lemaitre, R., Retzlaff,B., Childs, M., and Knopp, R. H. (1995). Dietary intake and cellmembrane levels of long-chain n-3 polyunsaturated fatty acids and therisk of primary cardiac arrest. Journal of the American MedicalAssociation 274, 1363–7.

Sunarya, M., Hole, M., and Taylor, K. D. A. (1996). Methods ofextraction composition and stability of vitamin A and other componentsin dogfish (Squalus acanthias) liver oil. Food Chemistry 55, 215–20.

Volkman, J. K., and Nichols, P. D. (1991). Applications of thin layerchromatography-flame ionisation detection to the analysis of lipids andpollutants in marine and environmental samples. Journal of PlanarChromatography 4, 19–26.

Manuscript received 27 October 1997; revised and accepted 6 March 1998

PUFA-containing liver oils from Australian sharks

Table 3. Proportion of major polyunsaturated fatty acids (PUFAs),sum of major PUFAs (% of total fatty acids) and component ratios for

shark liver oils and commercial capsule oilAA, arachidonic acid; EPA, eicosapentaenoic acid; DPA, docosapent-aenoic acid; DHA, docosahexaenoic acid. AA present at <1% in MaxEPA,

included with EPA

Fatty acid Percentage compositionGummy School White-spotted MaxEPA

shark shark spurdog

20:4(n–6) AA 4.0 2.9 0.4 – 20:5(n–3) EPA 9.3 9.9 3.9 17.922:5(n–3) DPA 2.2 2.8 2.7 2.222:6(n–3) DHA 16.2 16.4 11.3 10.9

Sum of PUFAs 37.0 37.3 24.3 41.2ratio of EPA:DHA 0.57 0.60 0.35 1.64ratio of w3:w6 4.2 8.9 7.9 7.5

http://www.publish.csiro.au/journals/mfr