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Trace metals in fish roe from the Mauritania coast
Volume18/Number9/September 1987 Nishimura, M. & Baker, E. W. (1986). Possible origin of n-alkanes with a remarkable even to odd predominance in recent marine sediments. Geochim. Cosmochim. Acta 50,229-305. Sleeter, T. D., Butler, J. E. & Barbash, J. E. (1978). Hydrocarbons in sediments of Bermuda region: Lagonal to Abyssal depth, in ACS
Series No. 185, American Chemical Society, Washington, D.C. We±re, D. H. & Ebhardt, G. (1968). Distribution of long chain n-paraffins and n-fatty acids in sediments from the Persian Gulf. Geochim. Cosmochim. Acta 32,465-466.
11025-326X/87 $3.00+0.00 © 1987 Pergamon Journals Ltd,
Marine Pollution Bulletin, Volume 18, No. 9, pp. 507-508, 1987. Pnnted in Great Britain.
Trace Metals in Fish Roe from the Mauritania Coast Trace metals (Cd, Pb, Hg, Cu, Fe, Mn, and Zn) were analysed in fish roe from the northern coast of Mauritania (Atlantic Ocean, 20*N, 16"W). Fish roe is important for the economy of this country since it is consumed locally and represents quite an important part of Mauritanian exports to European countries, especially France. No information is available concerning the trace metal concentrations of fish roe from this area. In Mauritania, fish roe is collected by fishermen from mullets, essentially Mugil cephalus (common grey mullet) living in the brackish waters of the coastal laguna of Arguin. This is 'hard' roe from the female consisting of maturing oocytes. After collection, fish roe is salted, dried, and pressed as a flat sausage. For long storage, it is wrapped in paraffin. Salted fish roe, wrapped in paraffin, was bought at the market in Nouakchott. Samples were put in plastic bags and kept at 40C until analysis. In the laboratory, the preparation of the samples was carried out under a laminar flow hood. Paraffin was peeled off the samples which were dried to a constant weight at 60°C and ground in a teflon mortar. For mercury determinations, samples (1-3 g dry wt) were digested for 3 h at 140°C with concentrated nitric acid (65% wt) in teflon-lined, high pressure decomposition vessels. The digested samples were cooled and transferred to 50 ml flasks and diluted to volume with deionized distilled water. Total mercury was determined by a Coleman Mercury Analyzer, MAS-50 according to the method described in Hatch & Ott (1968). For the other metals, digestion (1-3 g dry wt of samples) was carried out in teflon beakers with nitric acid (65% wt) for 3 h. The resulting solution was evaporated to dryness and redissolved in 0.1 N hydrochloric acid. Cadmium and lead determinations were carried out with a PAR 264 A voltammetric analyser connected to a PAR 303 static mercury drop electrode. Copper, iron, manganese, and zinc were determined directly on the digested solution by flame atomic absorption spectrophotometry (Philips, Pye Unicam SP9). The analytical procedure was checked using standard reference material (lobster hepato-pancreas) provided by the National Research Council of Canada. Results of the analyses are given in Table 1. Our results are in agreement with the certified values. Trace elements such as cadmium, lead, and mercury exhibit low concentrations in mullet fish roe (Table 2).
TABLE l
Comparison of metal concentration in Standard Reference material (lobster hepato-pancreas)withour data 0tg g-i dry wt). Metal Cd Pb Hg Cu Fe Mn Zn
Valuesgivenby NRC (Canada) 26.3 10.4 0.33 439 186 23.4 177
± + ± ± ± ± ±
2.1 2.0 0.06 22 ll 1.0 10
Our values 24.1 9.5 0.35 420 194 25.1 162
± 0.6 + 0.6 ± 0.06 ± 20 ±20 ± 0.8 ± 10
Meanvaluesof fivedeterminationsare given(± 1 standarddeviation). Among essential trace metals, zinc seems to be particularly concentrated in mullet fish roe, followed by iron, whereas copper and manganese exhibit relatively low concentrations. There is little data available concerning the levels of trace metals in fish roe (Table 3). The most extensive data were published by Julshamn et al. (1978) analysing cod roe from northern Norway. The authors reported that mature cod roe had the highest percentage of dry matter: 30.5% among the edible parts of this fish and the concentrations of metals they found compare favourably with our results (Tables 2, 3). According to the results of Julsham et al. (1978), essential trace elements are enriched in the cod eggs compared to the fish fillet (muscle) by a factor 14 for zinc, 6 for manganese, 4 for iron, and 2 for copper whereas toxic metals are slightly depleted in eggs with respect to the fish muscle. Amiard et al. (1980) reported that the eggs of the fish Syngnathus rostellatus contained less lead and especially less cadmium and more zinc and copper than the adults. Results reported here were compared to the data published by Windom et al. (1973) and Bebbington et al. (1977) on metal concentrations in muscle from the adult fish Mugil cephalus from North Atlantic and from Pacific, respectively. Zinc concentrations in the roe (Table 2) seem to be enriched ca. 10 times relative to the concentrations in the muscle (Table 3). Cadmium, copper, lead and mercury appear not to be especially concentrated in the mullet roe compared to the adult muscle (Table 3). No published data was available for iron and manganese concentrations in the fish Mugil cephalus. There was no significant difference in iron and manganese concentrations between mullet roe and a wide range of adult fish (Tables 2, 3). The enrichment factor of 10 found for zinc in mullet roe may be explained by the well-known physiological role of zinc in fertilization. Julshamn & Braekkan (1976) 507
Marine Pollution Bulletin TABLE 2
Concentrations of trace metals in mullet roe (rag g-~ dry wt). Sample Mullet roe n = 10
Cu
Fe
Mn
Zn
Cd
Hg
Pb
2.3 +0.5
21 ±4
2.1 ±0.5
142± 12
< 0.1
-< 0.07
< 0.5
TABLE 3
Concentrations of trace metals in cod roe and in the muscle of Mugil cephalus and of other fish species (tag g-~ dry wt). Sample
Cu
Fe
Mn
Zn
Cd
Hg
Pb
Cod roe
2.07
29.5
2.6
147
0.003
0.06
0.16
Muscle of Mugil cephalus
17 4.30
Muscle of fish
21 6.1-31.9
0.4-2.5
found that the zinc level in the ovary of the cod was higher than in any other organ of the fish. Moreover, juvenile cod roe was found to have 3 times more zinc than mature cod roe (Julshamn et al., 1978). Feeding habits may influence trace metal concentrations in fish and consequently fish roe. The common mullet is an herbivore which may be partially detritivorous (Bougis, 1976). Metal concentrations in mullet roe are lower than those reported for plankton and particles (H~irdstedt-Rom6o, 1980, 1982; Romdo, 1985) implying that there is no biomagnification along the food chain. Total mercury concentrations in mullet roe are far below the limit recommended by FAO/WHO of 0.5 ~g g-~ fresh weight (ca. 1.5 p.g Hg g-~ dry wt) for foodstuffs. The same holds true in respect of the other metals studied. The work demonstrates that the concentrations of seven elements in mullet roe do not have high levels except zinc which presents relatively high but acceptable quantities. In conclusion, the levels reported here may be taken as a convenient base line against which any future pollution trends might be measured, the area considered being for the moment free of large urban and industrialized centres along the coastline.
M. ROMEO
INSERM U 303, B.P 3, La Darse, 06230 Villefranche-sur-mer, France
508
References Julshamn etaL, 1978 Windom etal., 1973
0.20
0.15
3.55
Bebbington etal., 1977 Eislcr, 1981
This work was supported by the lnstitut National de la Same et de la Recherche M6dicale. INSERM U.303 Mer et SamE. I am indebted to M. Gnassia-Barelli for carrying out polarographic determinations of cadmium and lead. I thank C. and R. Caruba who provided the fish roe while they were in Nouakchott within the framework of an agreement between the Mauritanian government and the University of Nice. Amiard, J. C., Amiard-Triquet, C., MEtayer, C. & Marchand, J. (1980). Etude du transfert de Cd, Pb, Cu et Zn dans les chaines trophiques ndritiques et estuariennes. I. Etat dans l'estuaire interne de la Loire (France) au cours de FEtE 1978. War. Res. 14,665-673. Bebbington, G. N., Mackay, N. J., Chvojka. R., Williams, R. J., Dunn, A. & Auty, E. H. (1977). Heavy metals, selenium and arsenic in nine species of Australian commercial fish. Austral. J. Mar. Freshwater Res. 28,277-286. Bougis, P. (1976). In Oc~anographie biologique appliquOe. L'exploitation de la vie marine. (Masson, ed.), pp. 1-320. Bougis, Paris. Eisler, R. (1981). In Trace metal concentrations in marine organisms, pp. 493-623. Pergamon Press, New York. HSxdstedt-RomEo, M. (1980). Zinc, copper and cadmium in zooplankton from the N.W. Mediterranean. Mar. Pollut. Bull 11, 133138. Hhrdstedt-RomEo, M. (1982). Some aspects of the chemical composition of plankton from the North-Western Mediterranean Sea. Mar. Biol. 70,229-236. Hatch, W. R. & Ott, W. L. (1968). Determination of sub-microgram quantities of mercury by atomic absorption spectrophotometry. Anal. Chem. 40, 2085-2087. Julshamn, K. & Braekkan, O. R. (1976). The relation between the concentration of some main elements and the stages of maturation of ovaries in cod ( Gadus morrhua). Fisk. Dir. Skr Ser. Ernaering 1, 115. Julshamn, K., Haugsnes, J. & Eriksen, J. (1978). Major and minor element (mineral) levels in products and offal from the fishing industries. Fisk. Dir. Sk r. Ser. Ernaering 1, 137-144. RomEo, M. (1985). Contribution h la cormaissance des mEtaux traces (Cd, Cu, Hg, Pb, Zn) dans l'EcosystEme marin au niveau du plancton. Approches analytiques et expErimentales. "l'hase d'Etat. UniversitE de Nice. Windom, H., Stickney, R., Smith, R., White, D. & Taylor, F. (1973). Arsenic, cadmium, copper, mercury and zinc in some species of North Atlantic finfish. J. Fish. Res. Bd. Can. 30,275-279.
Series No. 185, American Chemical Society, Washington, D.C. We±re, D. H. & Ebhardt, G. (1968). Distribution of long chain n-paraffins and n-fatty acids in sediments from the Persian Gulf. Geochim. Cosmochim. Acta 32,465-466.
11025-326X/87 $3.00+0.00 © 1987 Pergamon Journals Ltd,
Marine Pollution Bulletin, Volume 18, No. 9, pp. 507-508, 1987. Pnnted in Great Britain.
Trace Metals in Fish Roe from the Mauritania Coast Trace metals (Cd, Pb, Hg, Cu, Fe, Mn, and Zn) were analysed in fish roe from the northern coast of Mauritania (Atlantic Ocean, 20*N, 16"W). Fish roe is important for the economy of this country since it is consumed locally and represents quite an important part of Mauritanian exports to European countries, especially France. No information is available concerning the trace metal concentrations of fish roe from this area. In Mauritania, fish roe is collected by fishermen from mullets, essentially Mugil cephalus (common grey mullet) living in the brackish waters of the coastal laguna of Arguin. This is 'hard' roe from the female consisting of maturing oocytes. After collection, fish roe is salted, dried, and pressed as a flat sausage. For long storage, it is wrapped in paraffin. Salted fish roe, wrapped in paraffin, was bought at the market in Nouakchott. Samples were put in plastic bags and kept at 40C until analysis. In the laboratory, the preparation of the samples was carried out under a laminar flow hood. Paraffin was peeled off the samples which were dried to a constant weight at 60°C and ground in a teflon mortar. For mercury determinations, samples (1-3 g dry wt) were digested for 3 h at 140°C with concentrated nitric acid (65% wt) in teflon-lined, high pressure decomposition vessels. The digested samples were cooled and transferred to 50 ml flasks and diluted to volume with deionized distilled water. Total mercury was determined by a Coleman Mercury Analyzer, MAS-50 according to the method described in Hatch & Ott (1968). For the other metals, digestion (1-3 g dry wt of samples) was carried out in teflon beakers with nitric acid (65% wt) for 3 h. The resulting solution was evaporated to dryness and redissolved in 0.1 N hydrochloric acid. Cadmium and lead determinations were carried out with a PAR 264 A voltammetric analyser connected to a PAR 303 static mercury drop electrode. Copper, iron, manganese, and zinc were determined directly on the digested solution by flame atomic absorption spectrophotometry (Philips, Pye Unicam SP9). The analytical procedure was checked using standard reference material (lobster hepato-pancreas) provided by the National Research Council of Canada. Results of the analyses are given in Table 1. Our results are in agreement with the certified values. Trace elements such as cadmium, lead, and mercury exhibit low concentrations in mullet fish roe (Table 2).
TABLE l
Comparison of metal concentration in Standard Reference material (lobster hepato-pancreas)withour data 0tg g-i dry wt). Metal Cd Pb Hg Cu Fe Mn Zn
Valuesgivenby NRC (Canada) 26.3 10.4 0.33 439 186 23.4 177
± + ± ± ± ± ±
2.1 2.0 0.06 22 ll 1.0 10
Our values 24.1 9.5 0.35 420 194 25.1 162
± 0.6 + 0.6 ± 0.06 ± 20 ±20 ± 0.8 ± 10
Meanvaluesof fivedeterminationsare given(± 1 standarddeviation). Among essential trace metals, zinc seems to be particularly concentrated in mullet fish roe, followed by iron, whereas copper and manganese exhibit relatively low concentrations. There is little data available concerning the levels of trace metals in fish roe (Table 3). The most extensive data were published by Julshamn et al. (1978) analysing cod roe from northern Norway. The authors reported that mature cod roe had the highest percentage of dry matter: 30.5% among the edible parts of this fish and the concentrations of metals they found compare favourably with our results (Tables 2, 3). According to the results of Julsham et al. (1978), essential trace elements are enriched in the cod eggs compared to the fish fillet (muscle) by a factor 14 for zinc, 6 for manganese, 4 for iron, and 2 for copper whereas toxic metals are slightly depleted in eggs with respect to the fish muscle. Amiard et al. (1980) reported that the eggs of the fish Syngnathus rostellatus contained less lead and especially less cadmium and more zinc and copper than the adults. Results reported here were compared to the data published by Windom et al. (1973) and Bebbington et al. (1977) on metal concentrations in muscle from the adult fish Mugil cephalus from North Atlantic and from Pacific, respectively. Zinc concentrations in the roe (Table 2) seem to be enriched ca. 10 times relative to the concentrations in the muscle (Table 3). Cadmium, copper, lead and mercury appear not to be especially concentrated in the mullet roe compared to the adult muscle (Table 3). No published data was available for iron and manganese concentrations in the fish Mugil cephalus. There was no significant difference in iron and manganese concentrations between mullet roe and a wide range of adult fish (Tables 2, 3). The enrichment factor of 10 found for zinc in mullet roe may be explained by the well-known physiological role of zinc in fertilization. Julshamn & Braekkan (1976) 507
Marine Pollution Bulletin TABLE 2
Concentrations of trace metals in mullet roe (rag g-~ dry wt). Sample Mullet roe n = 10
Cu
Fe
Mn
Zn
Cd
Hg
Pb
2.3 +0.5
21 ±4
2.1 ±0.5
142± 12
< 0.1
-< 0.07
< 0.5
TABLE 3
Concentrations of trace metals in cod roe and in the muscle of Mugil cephalus and of other fish species (tag g-~ dry wt). Sample
Cu
Fe
Mn
Zn
Cd
Hg
Pb
Cod roe
2.07
29.5
2.6
147
0.003
0.06
0.16
Muscle of Mugil cephalus
17 4.30
Muscle of fish
21 6.1-31.9
0.4-2.5
found that the zinc level in the ovary of the cod was higher than in any other organ of the fish. Moreover, juvenile cod roe was found to have 3 times more zinc than mature cod roe (Julshamn et al., 1978). Feeding habits may influence trace metal concentrations in fish and consequently fish roe. The common mullet is an herbivore which may be partially detritivorous (Bougis, 1976). Metal concentrations in mullet roe are lower than those reported for plankton and particles (H~irdstedt-Rom6o, 1980, 1982; Romdo, 1985) implying that there is no biomagnification along the food chain. Total mercury concentrations in mullet roe are far below the limit recommended by FAO/WHO of 0.5 ~g g-~ fresh weight (ca. 1.5 p.g Hg g-~ dry wt) for foodstuffs. The same holds true in respect of the other metals studied. The work demonstrates that the concentrations of seven elements in mullet roe do not have high levels except zinc which presents relatively high but acceptable quantities. In conclusion, the levels reported here may be taken as a convenient base line against which any future pollution trends might be measured, the area considered being for the moment free of large urban and industrialized centres along the coastline.
M. ROMEO
INSERM U 303, B.P 3, La Darse, 06230 Villefranche-sur-mer, France
508
References Julshamn etaL, 1978 Windom etal., 1973
0.20
0.15
3.55
Bebbington etal., 1977 Eislcr, 1981
This work was supported by the lnstitut National de la Same et de la Recherche M6dicale. INSERM U.303 Mer et SamE. I am indebted to M. Gnassia-Barelli for carrying out polarographic determinations of cadmium and lead. I thank C. and R. Caruba who provided the fish roe while they were in Nouakchott within the framework of an agreement between the Mauritanian government and the University of Nice. Amiard, J. C., Amiard-Triquet, C., MEtayer, C. & Marchand, J. (1980). Etude du transfert de Cd, Pb, Cu et Zn dans les chaines trophiques ndritiques et estuariennes. I. Etat dans l'estuaire interne de la Loire (France) au cours de FEtE 1978. War. Res. 14,665-673. Bebbington, G. N., Mackay, N. J., Chvojka. R., Williams, R. J., Dunn, A. & Auty, E. H. (1977). Heavy metals, selenium and arsenic in nine species of Australian commercial fish. Austral. J. Mar. Freshwater Res. 28,277-286. Bougis, P. (1976). In Oc~anographie biologique appliquOe. L'exploitation de la vie marine. (Masson, ed.), pp. 1-320. Bougis, Paris. Eisler, R. (1981). In Trace metal concentrations in marine organisms, pp. 493-623. Pergamon Press, New York. HSxdstedt-RomEo, M. (1980). Zinc, copper and cadmium in zooplankton from the N.W. Mediterranean. Mar. Pollut. Bull 11, 133138. Hhrdstedt-RomEo, M. (1982). Some aspects of the chemical composition of plankton from the North-Western Mediterranean Sea. Mar. Biol. 70,229-236. Hatch, W. R. & Ott, W. L. (1968). Determination of sub-microgram quantities of mercury by atomic absorption spectrophotometry. Anal. Chem. 40, 2085-2087. Julshamn, K. & Braekkan, O. R. (1976). The relation between the concentration of some main elements and the stages of maturation of ovaries in cod ( Gadus morrhua). Fisk. Dir. Skr Ser. Ernaering 1, 115. Julshamn, K., Haugsnes, J. & Eriksen, J. (1978). Major and minor element (mineral) levels in products and offal from the fishing industries. Fisk. Dir. Sk r. Ser. Ernaering 1, 137-144. RomEo, M. (1985). Contribution h la cormaissance des mEtaux traces (Cd, Cu, Hg, Pb, Zn) dans l'EcosystEme marin au niveau du plancton. Approches analytiques et expErimentales. "l'hase d'Etat. UniversitE de Nice. Windom, H., Stickney, R., Smith, R., White, D. & Taylor, F. (1973). Arsenic, cadmium, copper, mercury and zinc in some species of North Atlantic finfish. J. Fish. Res. Bd. Can. 30,275-279.