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This paper not to be cited without prior reference to the author
International Council forthe Exploration of the Sea
C.M.1974/E:21FisheriesImprovement Committee
Ref. Shellfish & Benthos Committee
Seasonal Variations in the Organo-ehlorine content of
Shrimps and Oysters
by
Fr<'.ncco L.JFre.nlclin
Fisheries Laboratory, Burnham on Crouch, Essex
INT RODUCT ION
Sinee 1966 the Burnham laboratory has condueted a programme of
monitoring of the levels oforgano-ehlorine insecticide in marine
fish and shellfish. During the period January 1970 to December 1973
the programme was extended "to cover polychlorinated biphenyls (PCBs)
and six metals. The main purpose of the programme was to identify
long-term trends in residue levels and to identify areas where higher
concentrations occurred. However, in order to make this co~parison,
variation due to other factors must be taken into consideration.
Factors which could influence the concentration found in an animal
may be biological (e.g. nge, reproductive eycle,. ete) or envir.on
mental (e.g. ternperature or rainfall).The influence of aeveral
factors has been examined and the results of some of the work have
already been reported, for exnmple seasonal changes in the pest
icide content of oysters (Portmann, 1969) and variations of heavy
metal levels in fish due to age (Portmann and Neall, 1973). Since
1970 work has be~~ earried out in order to assess the sensonal
variations in the pesticide and PCB content of pink and brown
shrimps (Pandalus montagui and Crangon crangon). In the light of
the results of this, the oyster data (Portmann, 1969) have been
further exanined and results of both pieees of work are considered
in this paper.
MErHODS
Shrimps: Samples of pink and brown shrimps were taken at fortnightly
intervals during 1970, 1971, 1972 und 1973 from theestuary of the
River CrouOh (south-east England). A b lked sanpIe of 50 whole
shrimps of between 40 and 60 mfl total length was homogenized und a
L
10g sub-sample then nixed with sodiüfl·sülphate. This was extraeted
with n-nexane nhd prepared for,analysis, using thc method developed'
by Holden und Marsden (1969). 50 nl of the hexane extraet were
evaporated to dryness and the weight of residue was used to deternine
the "fat" eori"tEmt o'f-'the' samiüe. Pestieide arid pcif analysis was by
gas-liquid ehromatography (GLC), using'two 6ft x +inch OD glass
eolumns eontuL~ing 80-100 ~esh Chronosorb W AW DMCS eoated with
(a) 4% DC 200 + 6% QFI and (b) ff/o re 200.The pestieides identified were a'and ~ EHC, dieldrin, pp'DDE,
pp'TDE und pp'DDT; the PCB standard used was Aroc~lor 1254 to whieh
the GLC peaks in the shrinps bore a close rese .blanee.
Oysters: S~mples of European flat oysters (Ostre· edulis)were taken
at fortnightly intervals during 1967, 1968 und early 1969 fron the
estuaries of the River Croueh und its tributary the River Roaeh. The
tissue fron five oysters was bulked und honogenized und two 8g sub
sampIes were then mixed with sodiun sulphate. Pestieide analysis
was carried out in duplicate on each sub-sample, using the clenn-up
technique of de Faubert Maunder et al. {1964) followed by gas-liquid
chronatography. The GLC eolunns were 4 ft x t inch OD glass filled
with (a) 2.5% SE 301 + 0.25% Epik0te 1001 on ChrODosorb G, (b) 2%. .
Oronite Polybutene 128 + 0.2% Epikote 1001 on Gas Chron Q.:. Y'
Each sampIe was unalysed for a und. BHC, heptachlor epoxide,
aldrin, dieldrin, endrin, pp'DDE, pp'TDE and pp'PDT. Of these aldrin
and heptachlor epoxide were not recorded as being present, and endrin
oecurred in only a few sampIes fron the River Roaeh und then only at
very low concentrations.
RESULTS
The results of'the pink.shrinpsurvey are ShDwn in Fig. 1. For
much of the tine the fat und organo-ehlorine coneentrations follow a
similar pattern throughout the year, und both reach a peak during
July. However, atypieal peaks of fat content occurring in the autunn
are not always reflected in the organo-chlorine content. A similar
inerease in fat eontent during the summer has been noted in pink
shrimps fron the ~ash (Warren, 1972) and is thought to be due to a
conbination of factors, including egg-Iaying and noulting. It is weIl
knovrn that organo-ehlorine compounds concentrate in fatty tissue, and
2
,"
the rise in pestieide and PCB in shrinps is alnost eertainly linked
direetly to the inerease in fat levels.
A siniler relationship between fat and organo-ehlorine eontent
was noted in brown shrinps but the levels were nuch lowor and did not
show any regular seasonal variation (Fig. 2). No seasonal peak is
evident in fat eoneentration, probably beeause brown shrimps spawn
all the year round. The yearly range and Denn of fat and organo
ehlorine eonpounds in both pink and brown shrimps are h01fll in
Table 1. The lower coneentrations found in br01tn shrinps Day weIl
be linked to the lower f~t eontent.
Fig 3 sunnarizes the oyster data, ~nd hore peaks of organo
ehlorines often oeeur in June/July and Novenber/Deeenber, although
they are not ns striking as those found in the case of pink shrimps.
Unfortunately, no fat deterninations were carried out on the oyster
sanpIes, but an attenpt has been nade to link the peaks to biologieal
ehanges whieh could affect the pesticide eoncentration. Butler (1966)found that DUeh of the DDT in oysters was stored in the gonad, which
has a high fat content. Spawning in the east eoast Ostrea edulis
occurs in June/July (Orton, 1933), and it See s that 'the SUDner
peak of orgcillo-chlorines could weIl be associated with eg and
sper production and that the subsequent drop could be due to
spawning. The winter peak is aare difficult to explain. Walne (1970)studied seasonal changes in the condition 01 Ostrea cdulis fron the
River Roach. He found that the dry neat eondition index reaches a
peak during Septenber, 'but this does not e lain the winter peak
for pestieide vUlich oeeurs in Novenber/DeceDber. It is possible
that fat resources nay be built up in the late autunn after spawning,
and that these are utilized during the winter nonths when food
organisns are absent.
CONCLUSJQNS
Fron this study the sonsonnl variations in organo-chlorine levels
found in ~ink shrinps and oysters ap,ear to be attributed solely to
natur~l faotors. Pesticide spraying of c~op lands djacent to the
estu ry does not exrlcin the seasonnl variation, because nost of the
pesticides i1entified are no longer in use in thc U.K. and, noreover,PC)3
the/eoneerltrntion seeDS to follow the sCl.De trends as the pestieides.
3
In addition, if seasonal variations were due to crop spraying, then
increases in concentration would occur at the same tine and to the
sane extent in each s ecies.
Levels of all or ano-chlorine substances found in both shrinps
and oysters were generally low and no trend in nenn levels could be
detected over the period 1970-1973. The results of these investi
gations and of the previous work on netal levels in fish (Portnann
and Nealr", 1973), all denonstrate seasonal changes related to
biological factors; the results thus. enphasize the need to consider
natural factors when investigations are nade to deternine short
and long-tern trends of accunulation.
REFERENCES
BUTLER, P.A., 1966. The probIen of pesticides in estuaries. Spec.,PubI. Au. Fish. Soc., No.3, 110-115.
DE FAUBERT HAUNDER, M.J., EGAN, H., GODLY, E.I'!., HJ\.I'.1MOND, E.Vl.,ROBURN, J. and THOMSON, .I., 1964. Clean-up of anioal fatsand dairy rroducts for the analysis of chlorinatedpesticide residues. Analyst, Lond., 89 (1056), 168-174.
HOLDm~, A.V. and ~ffiRSDEN, K., 1969. Single-stage clean-up of aninaltissue extrncts for organochlorine residue analysis.J. Chronat., 44, 481-492.
ORT ON , J.H., '1933. Observations and experinents on sex-change inthe European oyster (O.edulis). Part 111 On the fate of theunspnwned ova. J. [')ar~ biol. Ass. U.K., 12 (1), 1-5.
PORTMAlnq, J.E., 1969. Further dnta on the occurrence of pesticidesin oysters. ICES CM 1969/E:8 (nineo).
PORT~mNN, J.E. and NEALL, P., 1973 The relntionship between ngeof fish and the levels of accunulatcd substances. lCESCM 1973/E:12 (nineo).
WALNE, P.R., 1970. The s ~sonal variation of Deut and glycogen contentof seven populations of oysters Ostrea edulis L. and a reviewof the literature. Fishery lnvest., Lond. Sero 2, 26 (3), 35pp.
1'lARREN, P. .I., 1972. Oil storage and shrinp density in Pandalusnontagui: are these factors which influence landings in acoomercial fishery? ICES CM 1972/K:18 (mimeo).
4
,
Table 1 Yearly range and mean values (in p2rentheses) for organo-chlorine pesticide, PCB and fat inpink and brown shrimps from the River Crouch (all except fat in parts/l 09 on n wet weight basis).
\'pp~DDE pp~TDE pp~DDT %fat
Year Q: BHC EHC dieldrin PCB
Pink Shrimps
1970 <1.0 - 7.0 <1.0 - 4.0 <1.0 - 29.0 <1 .0 - 13.0 <1.0 - 19.0 <1 .0 - 9.0 <50.0 - 200.0 <0.2 - 2.4«3.0) «2.0) «5.0) «3.0) «4.0) «5.0) «82.0) «0.9)1971 <1.0 - 6.0 <1 .0 - 7.0 4.0 - 22.0 2.0 15.0 <2.0 - 6.0 89.0 - 300.0 <0.2 .. 3.0«2.0) «2.0) (12.0) (7.0) «3.0) (200.0) «1 . 1)1972 <1 .0 - 3.0 1.0 - 3.0 <1.0 - 7.0 5.0 - 20.0 <1.0 - 9.0 <'I .0 - 4.0 64.0 - 280.0 0.2 - 2.4«2.0) (2.0) «5.0) (12,0) «5.0) «2.0) (170,0) ( 1. 1)1973 <1 .0 - 3.0 1.0- 6.0 <1.0 - 9.0 5.0 - 22.0 <1.0 - 9.0 <2.0 - 6.0 74.0 - 240.0 <0.2 - 2.4«2.0) (2.0) «5.0) (11.0) «4.0) «3.0 ) (160.0) «1 . 2)
Bro\1fn Shrimps
1970 <1 .0 - 4.0 <1.0 - 6.0 <1.0 - 3.0 <1.0 - 4.0 <1.0 - 5.0 <1 .0 - 7.0 <1 .0 - 110.0 <0.2 - 1.7«1 . 0) «2.0) «1 . 0) «1 . 0) «2.0) «2.0) «36.0) «0.4)1971 <1.0 - 3.0 <1.0 - 4.0 <1.0 - 5.0 <2.0 .. 3.0 <2.0 - 4.0 <24.0 - 44.0 <0.2 - 0.6«1 . 0) «2.0) «2.0) «2.0) «3.0) «31 .0) «0.4)1972 <1.0-3.0 <1.0 - 4.0 <1.0-3.0 <1.0 - 7.0 <1.0 - 6.0 <1.0 - 4.0 <17.0 - 48.0 <0.2 - 1.0«1.0) «2.0) «1 . 0) «3.0) «2.0) «2.0) «29.0) «0.5)1973 <1.0 - 2.0 <1.0 - 3.0 <1.0 - 4.0 <1.0 - 5.0 <1.0 - 3.0 <1.0 - 3.0 <15.0 - 43.0 <0.2 - 1.2(1. 0) «2.0) «1 . 0) «3.0) «2.0) «2.0) «21.0) «0.7)
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