PROC. N.S. INST. SCI (1986)
Volume 36, pp. 107-113
AN INITIAL INVESTIGATION OF LIPIDS AND FATTY ACIDS
OF NOVA SCOTIAN "SOFT" COD
R.G. ACKMAN, AND W.M .N. RATNAYAKE
Canadian Instit ute of Fisheries Techno logy
Technical University of Nova Scotia
Halifax, Nova Scotia
83) 2X4
T. O HSHI MA
Tokyo University of Fish eries
5-7, Kanan 4, M inato-ku
Tokyo 108, japan
P.]. KE
Fisheries and O ceans Canada
P.O. 550
Halifax, Nova scotia
83) 257
" Soh " cod Gadus morhua are a regular economic problem in fisheries on the Scotian Shelf. A
preliminary study has been conducted and a low fat content in viscera is the principal abnormality.
The lipid content, lipid class profil es, and fatty acids of the fillets from two "soh oily" cod were also
examined in this study and were relatively similar to those of one "control" fish as well as t o"normal"
Atlantic cod. It was however observed that t he fatty acid details of the soh oily cod were slightly
different from those in t he literature for " normal" Atlantic cod. The aquarium-held control fish
supplied by Fisheries and Oceans Canada also had a slightly different fatty acid composition. Lipids
could not be directly associated with the soh cod condition.
La presence de cabillaud " mo u " est un probleme economique frequent dans les peche ri es de Ia
plate-forme "Scotian". Une etude preliminaire a montre que l'abnormalite principale estle teneur en
lip ides bas des viscer es. Le ten eu r en lipides, le profile de classe de lipides, et des acides gras des fil ets
de de ux capabillauds " moux et gras" etaient examine dans cette etude et on ete relativement
simi laires a ceu x d'un poisson de controle aussi b ien qu'a ceux d' un cabillaud d' Atlantique " nor male". Cependant, o n a remarqueque les details desacidesgras de ces cabillauds etaientlegerement
d ifferentes de celles trouvees dans Ia litterature pour le cabi llaud d 'Atlantique " normale". La composition des acides gras du poisson fourni par Ia Departement de Peches et d 'Oceans du Canada et
maintenu en aquari um etait aussi legerement differente. La condition des cabillauds " moux et gras"
ne pouvait pas etre lies directe ment aux lipides.
Introduction
" Soft" cod is a seaso nal and localized problem in the Nova Scotian fishing industry
but o f unknown etiol ogy. In mid to late su mmer, and usuall y in specific areas, fo r
example the Emeral d Bank, cod Gadus morhua can be taken but are difficult to
handl e and/ or process because of the "soft" musculature. This condition is sometimes appare nt wh en the fish are caught, but it m ay also develop after a few days on
ice, and ca n occur in haddock and other species. Fisher men avoid known soft cod
areas and often have to go fu rth er afield to catch cod. It is th erefore an econo mi c
probl em of some significa nce.
Previo us investi gations by Fisheri es and O cea ns Ca nad a showed that no known
disease, pro tozoa n, o r baderial infection could be associated with th e soft cod
problem. The observati on that suc h fish were feeding heavily, ofte n on sand lau nce
108
ACKMAN, RA TNAYAKE, OSHIMA AND KE
Ammodytes american us, suggested a dietar y fad or. In an exam inat io n of sa nd launce
oil (Ackman and Eaton 1971) a non-saponifable content of 2.4% was noted, but the
mat erial was not defined. This was higher by a fad or of 2 to 4 than for herrin g o ils, and
agreed w ith a report of 3.56% of unsaponifiable material in North Sea sa nd launce
(Holmer 1967). Thi s suggested an investigation of lipids as a starting p oint for the soft
cod problem.
Occasional reports of soft cod or haddock having a dimethyl sul fid e odor (cf.
Ackman et al. 1967) also suggested a d ietary factor, but not necessarily lipi d -oriented.
Materials and Methods
Fish samples
Fillets, stomachs and all other viscera from seven cod sa mples were su pplied to the
Canad ian In st itute of Fisheries Techno logy o n 25th October, 1984 by Fisheri es and
O cea ns Canada, for anal yses for lipid content and lipid class an d fatty acid profiles.
Out of t hese seve n fis h, four were categorized by Fisheries and Oceans Ca nada as
" soft oily" cod. The other three were con trol fish, from stocks maintained in the
Fisheries and Ocea ns aquarium in Halifax. Fi sh described as d ressed had been gutted
prior to receipt and viscera were not available. The cod e names and t he descri ption of
the samples are give n i n Table I.
Analyses
Th e lipi ds were ext raded with chloroform: methyl alcohol: wat er accordin g to the
Bligh and Dye r (1959) procedure. The recovered lipids were analysed for lipid class
compositi o n by the l atrosca n (Technical Marketing Ass.) tec hnique (Ac kman 1981).
Chromarods-S were developed i n hexane: d iethyl ether: formic acid 97:3: 1 (v/v/v).
Some selected total li pid samp les were tra n sesterified with boron trifluoride: methyl
alcohol (Morri so n and Smith 1964). The recovered fatt y acid meth yl esters were
examined b y Gas-liquid ch ro matography (G LC) on a Su pelcowax -10 (Supelco Canada Ltd. ) fused si li ca cap illary column, 50 m x 0.24 mm, as described b y Ackman (1986).
Table I Descri ption of the samples and their lipid percentages
% Lipid (w/ w )
Sa mpl e*
Fillet
Dressed S0-1
Round S0-2
Dressed S0-3
Round S0-4
Round C0-1
Round C0-2
Dressed C0-3
0.77
0.71
0.61
0.63
0.68
0.64
0.67
• SO ="soft, oily" fish
CO= control fish
•• including liver
- Not determined
Viscera• •
Stomach and
Contents
13.4
0.98
16.2
55.3
36.6
2.04
4.82
1.85
FATTY ACIDS OF SOFT COD
109
Results and Discussion
Th e lipid perce ntages, lipid co mpositions and t he fatty acid compositions of the
various cod sa mples are give n in Tables I, II and Ill respectively.
Th e latroscan flam e ion izatio n detector area responses for fillets (Table II ) were
heavi ly biased by the dominance of the phospholipids. Conversely, lipids of the
viscera and sto machs were dominated by trigl ycerid es. They ar e therefore reported
simply as area % since normal correction procedures (Parrish and Ack man 1985)
would have been very difficult to apply.
An un expected res ult was the very low lipid content of the viscera of two soft cod
(Tab le 1). It sho uld be noted that th e lipid content in t he viscera is va riable, depending
mainly on the nutritional and reproductive status of the fi sh. Th e viscera did not
includ e rip e or ripenin g gonads and therefore the li ver was quantitative ly th e most
important com po nent. The li ver is norm all y 30-50% fat and p lays an important role in
the " co nd iti o n" of the fish (Jangaard et. al. 1967a). As expected th e visceral lipids f ro m
the two contro l sa mples were mostly triglycerides, w hereas those of the soft oily cod
showed o nl y about 90% triglycerides, the rest being mostly phospholipids (Table II).
In a st udy of Nova Scotian cod li vers (O'Keefe, 1984) on ly 3 of 71 livers had less than
25% lipids.
The variations in the stomach lipid composit ions (Tab le II) are apparently d ue to
the different types of food in the stomachs. The lipid content in t he sto machs were
low an d va ried from 0.98 to 4.82%. Visua l examinati o n of the soft oily cod (S0-2 and
S0-4) showed some undigested clams and fish bones in their stomachs. The stomach
con te nts of the control f ish could not be identified by visual examinations. They are
normall y fed chopped herring, su pplemented wi th beef li ver.
Table II Lipid composition of the cod samples as determined by the lat rosca n TLC/ FID
Sa mple
Fillets
Dressed 50-1
Round 50-2
Dressed 50-3
Round 50-4
Round C0-1
Round C0-2
Dressed C0-3
latroscan Area % •
FFA t
TG
SE
FFA**
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
TR
C HL
Pl
1.4
5.4
4.3
TR
4.7
3.5
1.7
98.6
94.6
95.7
100
95.3
96.5
98.3
Viscera
Round
Round
Round
Round
50-2
S0-4
C0-1
C0-2
90.8
90.4
100
100
TR
TR
1.2
83.4
95.1
56.7
15.5
2.7
TR
4.1
9.2
9.6
TR
Stomach
Round
Round
Round
Ro und
S0-2
S0-4
C0-1
C0-2
1.7
TR
3.3
2.6
TR
TR
4.5
78.9
13.9
4.9
29.5
• The latrosca n TLC/ FID responses were not corrected to w / w%. TR, trace; SE, steroid este rs;
FFA, free fatty acids; TG, triglyceridecs; CHL, ch olesterol; Pl, phospholipid.
•• Primarily saturated acids (e.g. 16:0).
t Primaril y polyunsat urated acids (e.g. 22:6n3).
110
AC KMAN, RAT NAYA KE, O SH IMA A N D KE
Table Ill Fatt y acid composition of total lipids of selected cod samples in w/ w %.
Facty•
Acid
14:0
lso 15:0
15:0
lso 16:0
Anteiso 16:0
16:0
17:0
lso 18:0
18: 0
19:0
20:0
Total sa tu rates
Fillet
50-2
Fi lle t
50-4
Fillet
C0-2
Viscera
50-2
2.6
2.9
6.0
0.7
0.6
0.7
29.2
0.3
0.2
3.8
0.2
32.0
0.2
0.1
3.9
0.2
24.1
0.3
0.2
2.6
0.1
<0.1
7.9
0.7
0.9
0.3
0.3
17.9
0.3
0.2
2.0
<0.1
21.6
0.8
0.3
5.4
0.2
0.1
Stomach
50-2
6.0
1.2
37.0
39.9
34.0
30.5
35.6
2.4
0.5
2.4
0.4
5.2
0.6
12.3
0.4
6.5
4.0
0.3
0.3
1.4
0.1
5.7
2.8
0.3
0.2
1.4
0.1
12.4
3.0
0.5
0.7
4.0
0.1
0.2
<0.1
0.6
1.0
0.1
0.1
0.3
12.6
5.1
0.4
1.3
5.9
0.5
0.1
0.5
0.5
0.1
0.2
5.8
0.4
0.3
8.3
3.2
0.3
3.2
2.6
0.3
0.1
0.3
0.3
0.1
0.2
15.7
14.0
27.9
42.8
27.2
0.1
1.1
0.1
0.2
0.7
0.1
0.4
2.0
0.1
0.7
1.3
0.2
0.1
0.1
0.1
0.2
0.5
1.1
0.9
0.2
0.8
0. 2
Total dienes
1.4
1.1
2.6
2.4
3.7
16:3n4
18:3n6
18:3n 4
18:3n3
0.3
0.1
0.1
0.3
0.1
0.1
0.1
0.2
0.2
0.1
0.1
0.3
0.4
0.1
0.2
0.7
0.2
0.2
0.2
16:1n7
16:1n5
18:1n11
18:1n9
18:1 n7
18: 1n5
20: 1n11
20:1n9
20:1n7
22:1n5
22: 1n11 + 13
22: 1 n9
22:1n7
24:1n9
Total monoenes
16:2n6
16:2n 4
18: 2n6
18: 2n4
20: 2NMID
20:2n6
The level of fill et li pids i n the prese nt st u dy fe ll w it h in th e ra nge o f va lues ex p ecte d
(0.5-0.7%) fo r Atl antic cod, Gadus morh ua (Ja n gaard et. a l. 1967a; Ad d iso n e t. a l. 1968).
There was no a ppa r ent d iffere n ce in th e fill e t lip id levels b e twee n th e con trol a nd t he
soft o il sa m ples or in re lat ion to visceral lipid.
The lip id class co mposit io n s for the fi llets (Ta b le II ) a re all ge n e r ally simila r, except
fo r one soft oily cod (S 0 -4) wh ic h showed eve n more p hosp h o li pid th a n in th e ot he r
samp les. Probably th is fi n d in g was cor re la ted w it h a low visce ra l lipid. Ph osp h o lipid
FATTY ACIDS OF SOFT COD
111
Table Ill continued
Fatty
Acid
20:3n6
20:3n3
Fillet
50-2
Fillet
50-4
Fillet
C0-2
Viscera
50-2
0.1
0.1
0.1
<0.1
<0.1
0.1
Total trienes
16:4n3
16:4n1
18:4n3
18:4n1
20:4n6
20:4n3
22:4n6
Total tetraenes
Stomach
50-2
0.1
0.1
0.1
0.4
0.1
1.7
0.3
0.3
0.1
1.4
0.3
2.5
2.1
0.2
0.2
0.4
0.1
2.5
0.3
0.4
0.5
0.5
1.5
0.2
0.4
0.4
0.2
0.2
0.6
0.1
2.2
0.3
0.2
4.0
3.1
3.6
2.5
12.1
0.6
0.4
1.6
18:5n3
20:5n3
21 :5n3
22:5n6
22:5n3
17.1
0.3
0.6
0.8
16.9
0.5
0.4
1.4
12.3
0.3
0.3
1.3
0.1
8.1
0.3
0.2
1.0
Total pentaenes
18.8
19.2
14.2
9.7
17.2
24.0
224.8
23.6
220.9
16.5
188.1
10.3
149.9
12.5
179.6
22:6n3
Calc. iodine value
• Fatty acid notation indicates: Number on left of colon is the number of carbon atoms in the
fatty acid chain ; on the right of the colon, the number of ethyle nic bonds; the number to the
right of " n" is the position of the ethylenic bond nearest to the terminal methyl grou p.
was th e major lipid compo n e nt in all the fi llet sa mples, and sterol was t he o nly other
quantitatively important lipid co mponent. Tri glycerid e was found in small a mo unts in
al l samples and was found to be accompanied by a n equal amount of diacyl glyceryl
ethers (Ratnayake et al. , 1986), hit herto not reported for cod flesh lipids. It is concluded that there was possib ly mo re lipid in the fillet from t he soft oi ly cod tha n the
controls, but the small n u mber of samples precluded a definitive com parison.
The fatty acid profiles of five cod li pid samples are given in Table Ill. The fatty acid
com positions of the fillets from the two soft oily cod samples (S0-2 and S0-4) were
basically similar to those published by Jangaard et. al. 1967b and by Addison et. a l.
1968, in studies on t h e flesh lipids of Atlantic cod, but were different in impo rtan t
detai ls. Palmitic acid (16:0) at 29.2 and 32.0% was much higher than literatu re values
(ca. 20%). Conversely octadecenoic acids (18:1) at 10.8 and 8.8% respedively were less
t ha n previous totals of 12-13%. Of the two major polyunsaturated acids, 20:5n 3 at
about 17% was almost exadly the same as in previous reports, whereas 22:6n3 at
about 24% was less than previous reports of 30-33% from the two independent
studies.
Unexpectedly the fatty acid composition of the lipids from the contro l fish differed
fro m previous reports and was also different from the two soft oily cod. Accordi n g to
the Addison et. al. (1968) resu lts, the major fatty acids of male cod flesh are 16:0, 18:1,
20:5n3 and 22:6n3 w ith weig ht percentages of 19.6, 13.8, 17.0 and 29.8 respedively.
From the Table Ill res ults, it is clear that t he percentages of the above four major fatty
acids from the lipids of the contro l cod are distindly different. Especially, the contro l
112
ACKMAN, RATNAYAKE, OSH IMA AND KE
cod flesh lipi d showed relati vely low proportions o f 20: 5n3 and 22:6n3 and correspo ndingly was e nriched with monoethylenic fatt y acids. Unfo rtunately a sample of
only one fish is always suspect (Takahashi et. al. 1985) and a more th oro ugh in vestigati o n is indi cated. It should be noted that Jangaard et. al. (1967b) averaged 12seasonal
samp les and Addiso n et. al. pub lished averages from four fish of each sex. Wh ether
aquarium-held cod are reliable co mparison sa mpl es for lipid and fatty acid studies is
an open question.
The fatty acid co m positi o n of the viscera of S0-2 was similar to th at of normal
At lantic cod li vers (Jangaard et. al. 1967b; Addison et. al. 1968) with 16:0, 16:1, 18:1,
20:1, 22:1, 20:5n3, and 22:6n3 as major fatty acids. A novel fatty acid, 20:2 t>. 5, t>. 13 was
tentativel y identifi ed from the stomach of a soft o ily cod (S0- 2). This and other
non-m ethylene-interrupted fatty acids are mino r fatty acids among those of Atlantic
moll uscs and ot her invertebrates (Paradis and Ackman 1977). In this conn ection
Limacina helicina, a mollusc, is a known facto r in t he food web transfer of d i m ethyl-2carboxyethy/ sulfonium chloride and its breakd own prod uct, dimeth ylsulfide, to
economicall y val uable fish suc h as cod (Ackma n et. al. 1967; Bo tta et. al. 1985) or
mackerel (Ackman et. al. 1972). The acrylic acid accompanying the dimethylsulfide
could lead to protein breakdown post-mortem but th is li ne of investigation was not
pursued. Protease activity (Ando et. al., 1986) see ms more probable. These enzymes
are known to produce a "jellied" cond iti on in American plaice Hippoglossoides
plat essoides (Te mpl eman and Andrews 1956), o r in other species (Ko nagaya 1984).
Th ese preli minary results suggest th at alt hough the lipid content in fillets of "soft
cod" is similar to that r eported in th e literature for normal fish, the visceral lipid is
ab norma ll y low. There also appears to be abnormalities in the fatty aci d co mposition
of fillets of "soft cod", but substantiation of these inferences requires detailed studies
on lar ge samples of contro l fish and of "soft cod".
Acknowledgements
This work was supported in part by th e Development Branch o f Fisheries and
O cea ns Canada.
References
Ackman, R.G. 1981. Flame ionization detection applied to thin-layer chromatography
o n coated quartz rods. In Methods in Enzymology (ed ).M. Lowenstein). Academic Press, New York, pp. 205-252.
Ackman, R. G. 1986. WCOT (capilla ry) gas-liquid chromatography. In Analysis of Fats
and O ils (eds. R.). Hamilto n and J.B. Ru ssell). Elsevier Applied Science Publishers,
Lo ndon, pp. 137-206.
Ackman, R.G. and Eaton, C.A. 1971. Investigation of the fatt y acid composition of oils
and lipids from th e sa nd laun ce Ammodytes american us from Nova Scotia waters.
}. Fish. Res. Board Can. 28:601 -606.
Ackman, R.G., Hingley, J. and May, A.W. 1967. Dimet hyl-bet a-propiothetin and
dimethyl sulfide in Labrador cod . }. Fish. Res. Board Ca n. 24:457-461.
Ackman, R.G., Hingley, J. and MacKay, K.T. 1972. Dimethyl sulfide as an odor
compone nt in Nova Scotia fall mackerel.}. Fish. Res. Board Can. 29:1085-1088.
An do, S., Hatano, M. and Zama, K. 1986. Prot ein degradation and protease activity of
chum sa lmon (O ncorhynchus keta ) muscle d uring spawning migration. Fish
Ph ysio logy and Biochemistr y, 1:17-26.
Addison, R. F., Ackman, R.G. and Hingley, J. 1968. Dist ributio n of fatty acids in cod
fles h lipids. }. Fish. Res. Board Can. 25:2083-2090.
FATTY ACIDS OF SOFT COD
113
Blig h, E.G. and Dyer, W.J. 1959. A rapid method of total lipid extradion and purifi cation. Can.}. Biochem. Physiol. 37:911-917.
Bo tta, J.R., Byrne, E.A. and Squires, B.E. 1985. Utilization of Atlantic Cod (Gadus
morhua) Judged to Have "Blackberry" Odor. Ca n. Tech. Rep. of Fish Aq. Sci. No.
1383, 11 pa ges.
Holme r, G. 1967. Studies over Danske Fiskoliers Sammensaetning. Fiskeriministeriets
Forsogslaboratori urn og Afd. for Biokemi og Ernaering. D.T.H. Kobenhaven, 150 p.
Jangaard, P. M., Brockerhoff, H., Burghe r, R. D. and Hoyle, R.J. 1967a. Seasonal
changes in general condition and lipid content of cod from inshore waters.}. Fish.
Res. Board Can. 24:607-612
Jangaard, P. M., Ac kman, R.G. and Sipos, J. C. 1967b. Seasonal cha nges in fatty acid
co mposition of cod liver, flesh, roe, and milt lipids. }. Fish. Res. Board Can.
24:613-627.
Ko nagaya, S. 1984. Studies on jelli ed meat of fish, with special reference to t hat of
yellowfin tuna. Bu ll. Tokai Reg. Fish. Lab. No. 114 (Abstrad in English of 5 pages).
Morrison, W. R. and Smith, L.M. 1964. Preparation of fatty acid methyl esters and
dimethyl aceta Is from lipids with boron fl uoride-methanol.}. Lipid Res. 5:600-608.
O' Keefe, S.F. 1984. Vitamin A, D and E in Nova Scotia Cod Liver Oi ls. M.Sc. Thesis,
Technical University of Nova Scotia.
Parad is, M. and Ackman, R.G. 1977. Potential for employing the distribution of
anomolous non-methylene-interrupted dienoic fatty acids in several marine
in vertebrates as part of food web studies. Lipids 12:170-176.
Parrish, C.C. and Ackman, R.G. 1985. Calibration of the latroscan Chromarod syste m
for marine lipid class analyses. Lipids 20:521-530.
Ratnayake, W. M. N., Ti mmins, A., Ohshima, T. and Ackman, R.G. 1986. Mass spectra
of fatty acid derivatives of isopropylidenes of novel glyceryl ethers of cod muscle
and of phe noli c acetates obtained with the Finnigan MAT ion trap detector. Lipids
21 :518-524.
Takahashi, K., lc hioka, K., Hatano, M. and lama, K. 1985. Seasonal variation of sardine
(Sardinops melanosticta) muscle lipids and other components. Bull. Fac. Fish.,
Hokkaido Univ. 36:248-257.
Templeman, W. and Andrews, G. L. 1956. Jellied condition in the American plaice
Hippolossoides platessoides (Fabrici us).]. Fish. Res. Board Can. 13:147-182.