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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