This paper not to be cited without prior reference to the authors

International Council forthe Exploration of the Sea

C.M. 1984/E:30Marine Environmental QualityCommitteeRef.: Mariculture Committee

•

TRACE CONTAMINANTS IN CATFISH RAISED

UNDER INTENSIVE CULTURE CONDITIONS------------------------------------------------------------------------

by

V. Hilge1), E. Huschenbeth2) and U. Harms 3)

1) Bundesforschungsanstalt für FischereiInstitut für Küsten- und BinnenfischereiAußenstelle, Wulfsdorfer Weg2070 Ahrensburg

2) Bundesforschungsanstalt für FischereiInstitut für Küsten- und BinnenfischereiPalmaille 92000 Hamburg 50

3) Bundesforschungsanstalt für FischereiLabor für Radioökologie der GewässerWüstland 22000 Hamburg 55Federal Republic of Germany

ABSTRACT

The European catfish (Silurus glanis L.) and the American catfish (Ictaluruspunctatus Raf.) were reared from the fingerling stage to the age of 2 and 5 yearsrespectively under intensive culture conditions in warm water of 23° - 26°C.They were fed on commercial trout pellets or on a mixture of eel feed meal andtrout offals.

Fillet, kidney and liver of animals of both species were investigated for certainheavy metals and chlorinated hydrocarbons. The results obtained showed thatcontaminant levels were low, i.e. far below the limits of acceptability forhuman consumption.

•

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SOMMA1RE

Contaminants en trace dans le silure eleve sous des conditions de cultureintensive.

Le silure europeen (Silurus glanis L.) et le silure americain (1ctaluruspunctatus Raf.) furent eleves a partir du degre de fingerling jusqu1a l'agede 2 a 5 ans sous les conditions de culture intensive dans l'eau chaudede 23 - 260 C.

1ls furent affourages avec de la nourriture en pilules pour les truites

d'usage courant ou avec une combinaison du fourrage d'anguilles et des tripesde truites.

Le filet, les reins et le foie de toutes les deux especes furent analyses surdes metaux lourds et sur des carbures d'hydrogene chlorures.

Les resultats obtenus indiquerent que les niveaux de contamination furent

inferieurs~ p.e. de loin a moins des limites acceptables pour la consommationhumaine .

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1. INTRODUCTION

Reports on the accumulation of trace:contaminants in fish, especially fromthe fresh water, have increased during the last years, and occasionallythe prohibition of selling catches on the market has been necessary

(Huschenbeth~ 1977, Krüger ~~., 1982" Kruse ~l~., 1983). In contrast tofishes from natural water bodies, rather little'is known aboutanimals in'intensive aquaculture ~nits raised ön artificial diets. Due to the origin and

treatment of the dietary ingredients, the possibility cannot be excluded, that, .

tface contaminants enter the cultured fish via the foodstuffs (e.g. fish oil)and/or the culture water with the consequence of the production of contaminatedfish.

In this study ~wo fish species (European and American catfish), which were ~

kept for up to 5 years in a recirculation system were investigated for certaintrace contaminants. The common practice of fish farmers to use fishoffals asadditional food to their cultured fishes has been looked for aS,well.Among the numerous potentially ecotoxic substances (contaminants) that enter

'the environment, attention has been focussed especially on heavy metals and

chlorinated hydrocarbons that are persistent in the environment. These substanceshave the tendency to be bioaccumulated in aquatic organisms at the varioustrophic levels. In this regard organisms that serve as food for man and whichare subject to contamination by such substances, could become a potential hazard

to man.

Consequently, it was the aim of this study to get an idea on the concentrationof certain heavy metals, organochlorine pesticides and polychlorinated biPheny~

of those parts of cultured catfish that are used for human consumption. As boththe European and the American catfish have some prospects for intensive culturein our region, it was our intention to see if and how culture conditions,including the use of artificial diets, may influence the amount of those

contaminants in the fillet. Additional analyses were performed on liver andkidney, because the mode of accumulation and sites of storage might be differentamong the species.

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2. MATERIAL AND METHODS

America~ catfi~h (Ictalurus punctatus Raf.) and European catfish (Silurusglanis L.) fingerlings of 5-10 9 were stocked in an experimental closed systemwith an activated sludge biofilter as treatment system of biodegradable matter.Water chemistry was checked"regularly for pH, ammonia,.nitrite, nitrate and

dissolved oxygen. The water temperature varied in the range of 23-26oC.Fresh culture water was added to avoid excess levels of nitrate being formedin the biofilter. The fishes were used for growth experiments. They were keptin 100 1, and at a bigger size in 800 - 1,600 1 plastik tanks at differentstocking densities. They were fed entirely on commercial trout pellets of adequatesize until an age of 5 (Ictalurus) and 2 years (Silurus) respectively.

Some specimens of 2-year old Silurus from an open system were obtained from aprivate fish farmer. These animals had been fed on a mixture of a commercialeel meal feed and trout offals to approx. equal parts from about 400 9 bodyweight on.

Samples of liver, kidney and muscle tissue were ana~ysed for the. heavy metals"mercury and cadmium, and for the polychlorinated hydrocarbons ~-chlordane,

r-chlor~ane,~-HCH, PCB, HCB, Dieldrin, Lindane, DDT, 000, and ODE.

Muscle tissue of the Silurus specimens fed on a mixture of eel meal and troutoffals ~as additionally analysed for methyl-mercury.

Sample preparation and analysis for organochlorine pesticides and PCB:Samples were homogenized and dehydrated by mixing the homogenate with anhydroussodium sulphate (Na?S04)' They were then subjected to solvent extraction in a2.: 1 mixture of n-nexane and acetone, for the extraction of lipids, organo­chlorine pesticides and PCBs.The extract was repeatedly cleansed through an alumina (Al?03) column, followedby fractionation through a silicia column. Compounds such as ~-HCH, Dieldrin,DDT and DDE were retained in the first fraction whilst DDE and PCBs wereretained in the second fraction. This method is described in detail by Holdenand Marsden (1969).Analysis of the final extracts for organochlorine pesticides and PCBs wascarried out by isothermal gas chromatography with a tritium electron cap­ture detector. The pesticides were evaluated by reference to correspondingstandard solutions, whilst the standard for PCBs was Aroclor 1254.

....-._----- -----------

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Sample preparation and analysis for heavy metals:For the determination of cadmium the orqanic material (fillet. liver and kidneytissue) was digested in HN03 under pressure in sealed vessels following themethod of Kotz et al.(1972). After acid digestion of the organic material. thetrace metal was~sOTated and preconcentrated by solvent extraction (Harms.1979) and fina lly determined by e lectrotherma1 (graphite furnace )atomicabsorption spectrometry.;-,.Analysis of total mercury was performed by a method describedbyHarms (1981).It employs pressure decomposition (see above) followed by cold-vapour atomicabsorption spectrometry. using nitrogen aeration. SnC1 2 reduction and pre­enrichment by amalgamation on a gold absorber.The analytical procedure for the chemical speciation of mercury includedselective reduction and subsequent cold-vapour atomic absorption spectrometryas well as gas chromatography after selective extraction of organicallyassociated mercury (methyl-mercury). For details of the method compare Harrns~2.!.. (1983. 1984).

•3. RESULTS AND DISCUSSION

Analyses were carried out on a total of 15 fish specimens. Data on contaminantlevels are summarized in Tables 1-4. The weight of the 2 years old European

catfish varied in the range of 600 - 1 280'9. and that of the 5 years old'. '

American catfish between 2 160 - 3 720 g. These animals have been grown ina recirculation system (Tables 1-3) .

. The weight of the European catfish raised in an open system on a mixture of eelmeal feed and trout offals ranges between 1 510 - 1 935 9 (Table' 4).

The influence of culture conditions and water quality on channel catfish in a

similar recycling system was investigated by Klinger ~l~. (1983). They couldnot find signs of severe stress among the fish used for their experiments. •The culture conditions in our case were similar to those cited above. Therefore.we assume that stress had very probably no significant influence on theaccumulation rate of trace contaminants and their distribution pattern withinthe animals analysed.

Organopesticides in the fillets of catfish exhibited very low levels (Table 1).Similar results were reported by Rosenthal ~2.!.. (1981) for trout and tilapia.

We found somewhat higher amounts of PCB in the catfish. especially in the livers

(Table 2). The·few data are not sufficient to establish a correlation betweenPCB levels in fillet and liver or in relation to the body weight.

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Direct comparisonof the data is difficult because in neither case continuousanalyses of.·the subsequent lots of feed have been performed. But it shouldbe stated:that 2 years or even 5 years of feeding artificial diets did notresult in unacceptable high amounts of polychlorinated hydrocarbons ·in themuscle.·A possible explanation could be the low fat content of these animalsof lessthan2% of fresh matter in the muscle (Huschenbeth, 1973, ICES 1977 a,band c, ICES 1980 a and b).

·The inner organs of fish, and especially liver and kidney, are known to be

sitesof accumulation of various contaminants. Feeding these to other fish mightin turn result in increased levels of contaminants in those fish. Therefore the

fillets of some Silurus were analysed to see if there was anyaccumulationthat.could beattributed to this food. The figures (Table 4) however demonstrate

• even lower .levels than those from the animals from the recycling system.

Earlier investigations on trace metal levels in marine and fresh water biota

(Harms, 1975, Stoeppler et al., 1979 a and b, ICES 1980 a and b, Krüger, 1981)suggest that with respect tofishes -regardless of their origin - cadmiumgenerally occurs in insignificant concentrations (ng/g range) in muscle tissue,but has the tendency to accumulate in liver and kidney tissue. These findingswere also reconfirmed by the present study .

. Acc~rding ·to·the respective acquired cadmium levels in liver and kidney (Table 3)Silurus ·and' Ictalurus show certain differences which may be related to differencesin a species-specific accumulation rate of the metal. Generally, it can be saidthat the fish specimens analysed did not carry alarmingly high levels of cadmiumin their inner organs and that the data thus far recorded are generally similar

to thos reported for other species in areas classified as unpolluted.

Numerous studies on mercury in coastal, oceanic and fresh water fish specieshave also provided basic information on the levels of contamination (IAEA, 1972,ICES 1977 a,b and C,· ICES 1980 a and b, Förstner et ~., 1979). For most speciesthe II natural ll background level seems to be in the region of 0.05 (or less)to 0,2 mg/kg (wet weight).

On the basis of this knowledge it can be stated that mercury did not accumulatesubstantially in fillets or inner organs of the fishes under the experimentalconditions chosen (Table 3). Even when using offals as diet no unacceptable high

mercurycontents could be found (Table 4).

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An interesting aspect of the present study is that only about 50% of·the totalmercury in muscle tissue of European catfish raised on offals wasin'thc organicform (Table 4). This contrasts with other observations indicating thatorganically associated mercury (methylmercury) is usually the;predominantchemical form in muscle tissue of marine and fresh water fish (Westtiö, 1966,

WesWö ~~., 1967, Holden, 1973, Linko ~~., 1977, Hattula ~~.,1978,

Cappon ~~., 1981).

What may be unique to the animals under study is the efficiency of demethylation

and/or excretion process, so that the transport of methylmercury to muscle tissue- the normal sequence following administration by food - does not occur or is

eonsiderably reduced. It is still unelear whether such "protective process"(biotransformation of methylmercury into the less toxie inorganic form

followed by its rapid excretion) exists or ~hether other factors have to be ~

taken into consideration.

The investigations carried out in the present study provide certain basicinformations that will be useful for future work on fish rearing under intensiveculture conditions. We can say that the fishes from our experiments were notexceptionally highly contaminated with bioaccumulating heavy metals andchlorinated hydrocarbons and that the concentration levels observed were farbelow those recognized as or suspected of a hazard to human health. In the lightof these findings further activities in this field of aquaculture seem to bepromising.

•

Acknowledgement:

This investigation was in part financed by the Federal Ministry of Researchand Technology (MFE 0510 3).

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4. LITERATURE

Cappon, C.J. and C.J.Smith: Mercury and Sel~nium Content and Chemical Form in. 1981 ' Fish Muscle.

Arch. Environm. Contam. Toxicol. 10: 305~319

Förstner~ u.; G.T.~. Wittmann : Metal Pollution in the Aquatic Environment.1979 'Berlin, Heidelberg, New York: Springer-Verlag

Harms, U.1975

The levels of heavy metals (Mn, Fe, Co, Ni, Cu,Zn, Cd, Pb, Hg) in fish from onshore and offshorewaters of the German Bight.Z. Lebensmittelunters. u.-Forsch. 157:125-132

•Harms,:U.]979

Harms, U~

1981

.'Harms ~ U~ • B. Luckas; W..,1983

Analytical procedures for the determination ofcopper~ zinc, cadmium, lead and total mercury inorganic material. In: Guidelines for the BalticMonitoring Programme for the First Stage. Edited by theScientific Expert of the Interim Baltic MarineEnvironment Protection Commission (from 3.5.80Helsinki Commission), Helsinki, Finland. Annex I: 1-15Beiträge zur Spurenanalyse von Quecksilber imNanogramm/Gramm-Bereich.Z. Lebensmittelunters. u.-Forsch. 172:118-122

Lorenzen and A. Montag: Analytik und Vorkommenanorganischer u~d organischer Quecksilberverbin­dungen in Meeres- und Landtieren.Fresenius Z. Anal. Chem. 316:'600 -603

Atomspektrometrische Methoden zur differenziertenBestimmung von anorganisch und organisch gebundenemQuecksilber in biologischen Materialien.In: B. Welz (Ed.): Fortschritte in der atomspektro­metrischen Spurenanalytik, Verlag Chemie, Weinheim,421 - 429

. .,',

Hattula, M.L.; J. Sarkka;1978

I

Harms, U.and B. Luckas1984

J. Janatuinen; J. Paasivirta and A. Roos: Total mercuryand methylmercury contents in fish from LakePaijanne .Environ .. Pollut. 17: 19

Holden, A.V., Marsden, K. : Single-stage clean-up of animal tissue extracts for1969 organo-chlorine residue analyses.

J: Chromat. 44: 481

•

Holden, A.V.1973

Mercury in fish and shellfish. A review.J. Fd. Technol. 8: 1-25

Huschenbeth, E.1973

Zur Speicherung von chlorierten Kohlenwasserstoffenim Fisch.Arch. FischWiss. 24: 105-116

- 8 -

Huschenbeth, E.1977

lAEA,1972

lCES1977 a

lCES1977 b

lCES1977 c

lCES .1980 a

lCES1980 b

überwachung der Speicherung von chlorierten Kohlen-wasserstoffen im Fi 5ch. . :; .Arch. FischWiss. 28: 173-186

Vienna 1972 Mercury Contamination in Man and hisEnvironment.Technical Report Series No. 137

A baseline study ofthe level of contaminating substancesin living resources of the North Atlantic.lCES, Coöp. Res. Rep. 69

The lCES coordinated monitoring programmes 1975 and 1976.lCES, Coop. Res. Rep. 72

Studies of the pollution of the Baltic Sea.lCES, Coop. Res.' Rep. 63

Extension to the baseline study of contaminant levels.in living resources of the North Atlantic.lCES, Coop. Res. Rep. 95

The lCES coordinated monitoring programme 1977.lCES, Coop. Res. Rep. 98

Klinger, H.; H. Delventhal and V. Hilge : Water quality and stocking density1983 as stressors of channel catfish (lctalurus punctatus

Raf. ) .Aquaculture ~ : 263 - 272

Kotz, L.; Kaiser, G.; Tschöpel, P.; Tölg, G.: Aufschluß biologischer Matrices1972 für die Bestimmung sehr niedriger Spurenelementgehalte

bei begrenzter Einwaage mit Salpetersäure unter Druckin einem Teflongefäß.Z. Anal. Chem. 260: 207-209

Krüger, K.-E. Untersuchungen zum Quecksilber-, Blei- und Cadmiumgehalt1981 in verschiedenen Organen von Fischen aus den Fluß- •

mündungsgebieten der deutschen Nordseeküste.Fisch und Umwelt 10: 33-48

Krüger, K.-E. and R. Kruse: Der Quecksilber-, Blei- und Cadmiumgehalt in Aalen1982 aus der Elbe und ausgewählten Vergleichsgewässern.

Arch. f. Lebensm.hygiene 1l:123-128

Kruse, R.; K. Boek and M. Wolf: Der Gehalt an Organochlor-Pestiziden und1983 polychlorierten Biphenylen in Elbaalen.

Arch. f. Lebensm.hygiene~: 81-86

Linko, R.R. and K. Terko: Occurrence of methylmercury inpike and Baltic herring1977 fram the Turku Archipelaga.

Environ. Pollut.: 14: 327

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Rosentha1 t H.; P.-D. Hansen and H. Bergmann: Accumu1ation of trace contaminants1981 in fishes raised in recricu1ation systems.

ICES t C.M. 1981:F:16 t 10 pp.

•

Stoepp1er t M.;1979 a

Stoepp1er t M.;1979 b

Westöö t G.1966

Va1enta t P.; Nürnberg t H.W.: App1ication of independent methodsahd standard materials: An effective approach to re1iab1etrace and ultra trace ana1yses of metals and metalloidsin environmental and biological matrices .

. Z• Anal. Chem. 297: 22-34

Nürnberg t H.W.: Comparative studies on trace meta1 levels in marinebiota. 111. Typica1 levels and accumu1ation of toxic tracemetals in musc1e tissue and organs of marine organismsfrom different European Seas.Ecotoxico10gy and Environm. Safety 1: 335-351

Determination of methylmercury compounds in foodstuffs.I. Methy1mercury compounds in fish; identification anddetermination. .Acta Chem. Scand. 28: 2131

•

Westöö t G. and K. Noren: Mercury and methylmercury in fish.1967 Vär Foeda 10:138

Table 1: Polychlorinated hydrocarbons (mg/kg fresh matter) in the fillets of the European catfish,Silurus glanis,(No. 1-5} and the American catfish, Ictalurus punctatus, (No. 6-10) fed on trout pellets

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No. Body weight oC- HCH PCB HCB Dieldrin Lindane DDT 000 ODE L DDT(g)

1 1 280 <0.001 0.044 <0.001 0.007 0.002 0.004 0.008 0.003 0.015

2 1 140 <O. 001 0.051 <0.001 0.010 <0.001 0.003 <0.001 <0.001 .0.0033 600 0.001 0.050 0.001 0.015 0.003 0.005 0.011 0.005 0.0214 710 0.001 0.237 0.001 0.008 0.007 0.004 0.013 0.008 0.025

5 840 0.002 0.387 0.001 0.003 0.006 0.019 0.009 0.009 0.037---- -------------- -------------------- ---------- --------- ---------- --------- --------- ----------

i- ________

6 2 160 0.009 0.170 -- 0.029 0.008 0.030 0.029 0.023 0.082

7 3 720 0.003 0.184 -- 0.011 0.005 0.023 0.016 0.018 0.057

8 3 130 0.014 0.148 -- 0.007 0.004 0.014 0.020 0.011 0.045

9 2 860 0.008 0.148 -- 0.013 0.006 0.013 0.023 0.022 0.058

10 2 300 0.005 0.054 -- 0.008 0.004 0.011 0.012 0.012 0.035

------ ------- : Not determined

......o

Table 2: Polychlorinated hydrocarbons (mg/kg fresh matter) in the livers of the European catfish,Silurus glani~! (No. 1-5) and the American catfish, Ictalurus punctatus, (No. 6-10)

-----iNo. 'Body weight c(~HCH PCB HCB Dieldrin Lindane DDT 000 ODE ~ DDT

• (g)

1 1 280 0.012 0.200 <0.001 0.123 0.090 0.015 0.043 0.017 0.075

2 1 140 0.004 0.100 <0.001 0.028 0.030 0.011 0.011 0.001 0.023

3 600 0.008 0.150 <0.001 0.090, 0.058 0.010 0.005 0.003 0.018

4 710 0.010 0.638 <0.001 0.120 0.040 0.043 0.055 0.023 0.121

5 840 0.008 0.104 <0.001 0.069 0.020 0.005 <0.001 0.003 0.008---- -------------f---------- --------- ---------f---------- --------- ---------f--------- f---------- -------6 2 160 0.023 0.105 <0.001 0.334 0.036 0.003 0.001 0.019 0.023

7 3 720 0.013 0.175 0.001 0.174 0.033 0.001 <0.001 0.012 0.013

8 3 130 0.061 0.153 0.001 0.261 0.026 0.006 0.049 0.031 0.086

9 2 860 0.012 0.107 <0.001 0.104 0.037 0.003 0.017 0.004 0.024

10 2 300 0.022 0.415 0.002 0.310 0.048 0.005 0.050 0.048 0.103

......

......

Tab~e 3: Heavy metals (mgjkg fresh matter) in fillet, liver and kidney of the European catfish,Silurus glanis, (No. 1-5) and the American catfish, Ictalurus punctatus, (No. 6~10)fed on traut pellets

No. Fi llet Liver ~!9~~~____________________----------------------- ----------------------. Hg Cd Hg Cd Hg Cd

I

1 0.024 0.001 0.022 0.28 0.022 2.1

2 0.021 0.001 0.029 0.36 0.013 2.8

3 0.022 0.002 0.016 0.20 0.012 2.2

4 0.037 0.002 0.016 0.18 0.011 1.8

5 0.024 0.001 0.020 0.46 0.014 3.2----- -----------~--------------------------~------------------------- .. - -~-----~-.-~----0.003 0.19

I0.061 0.031 0.276 0.027 I

II

0.14I

0.056 0.024 0.447 0.024 0.002 III

0.034 0.002 0.13I

0.069 0.024 0.418 III

0.001 0.17I

0.083 0.020 0.509 0.025 III

0.21I

0.050 . 0.031 0.4210 0.025 0.002 IIII

-- ---- ------------------------------------

Table 4: Polychlorinated hydrocarbons and heavy metals (all in mg/kg fresh matter) from the filletsof the European catfish, Silurus glanis, (No. 11-15) fed on a mixture of eel meal feedand trout offals

- - +)No. Body weight (~-Chlor- y-Chlor- .c-HCH PCB HCB Oieldrine Lindane fODT Cd Total Hg Methyl-

(g) dane dane Hg %

11 1 510 <0.001 <0.001 0.004 <0.010 <0.001 0.007 0.004 0.001 0.002 0.026 43

12 1 840 0.011 <0.001 0.006 <0.010 <'0.001 0.011 0.004 0.008 0.001 0.031 47

13 1 615 0.005 <0.001 0.004 <0.010 <0.001 0.003 0.003 0.006 0.001 0.048 52

14 1 665 0.005 <0.001 0.003 <0.010 <0.001 0.005 0.003 0.006 0.003 0.029 50

15 1 935 0.004 <0.001 0.004 0.029 <0.001 0.004 0.003 0.004 0.001 . 0.051 57

+) Methylmercury in %of total Hg

......w