STOUT: ORGANOCHLORINE RESIDUES IN FISHES 



Table 2.— iDDT and PCB in fishes from the northwest Atlantic Ocean and Gulf of 

 Mexico, nq = not queintifiable; nd = none detected. 



'Number of composites, each consisting of 10 fish. 



major component (—65%) accompanied by about 

 25% of the parent compound and 10% p,p'-TDE. 

 Although the composite picture for red snapper 

 looked markedly different (Table 3), in fact the 

 DDT residues in that species actually fell into two 

 categories. In the first group, p,p -TDE and p,p '- 

 DDT were not quantifiable, and the maximum 

 content of p,p -DDE was 0.029 ppm. In the second 

 group, five samples containing >0.029 ppm p,p'- 

 DDE, both p,p'-TDE and p,p -DDT were quanti- 

 fiable. In those five samples, the proportions of the 

 three components were the same as in the mack- 

 erel. Finfish from the Atlantic coast of Canada 

 (Sims et al. 1977) contained proportionately much 

 lessp,p -DDE (45% ) and morep,p -DDT (40% ) and 

 p,p '-TDE (15%). The increase in the proportion of 

 p,p -DDE in the present samples may reflect deg- 

 radation of the parent compound in the environ- 

 ment before it accumulated in the fishes. Samples 

 for the Canadian study were collected in 1971 and 

 1972, soon after usage of DDT had been drastically 

 curtailed (around 1970) as the result of increasing 

 insect resistance, problems with indirect con- 

 tamination of foodstuffs, and concern about effects 

 of DDT on nontarget species. Several years 

 elapsed before the samples for the present study 

 were collected, mainly in 1975. In the interval, 

 DDT was degrading aerobically to DDE and 

 anaerobically in the marine environment to TDE. 

 Alternatively, DDT may metabolize more rapidly 

 to DDE in the more temperate climate of the re- 

 gion studied and somewhat less rapidly to TDE. 



Table 3. — Mean proportions of 5^DDT present as p,p '-DDE, p,p '- 

 TDE, and p,p -DDT in fishes from the northwest Atlantic Ocean 

 and Gulf of Mexico. 



'Five samples which contained >0.029 ppm DDE. 



The concentration of PCB, when present, was 

 higher than that of IDDT in all samples but one. 

 The mean ratio of PCB to SDDT was 1.8 for gag, 

 2.2 for king and Spanish mackerel, and 2.6 for six 

 sets of red snapper. In the two other samples of red 

 snapper with quantifiable levels of PCB, the 

 PCB/SDDT ratios were 22.7 and 24.3. The con- 

 centrations of SDDT were below 0.01 ppm in both 

 cases. The one sample of red snapper in which the 

 PCB/IDDT ratio was below 1 contained a rela- 

 tively large amount of SDDT, 0.096 ppm, the sec- 

 ond highest IDDT value in the 18 samples of red 

 snapper. In contrast, the PCB concentration was 

 low both in absolute amount, <0.06 ppm, and in 

 rank, 14th out of 18 samples. 



The chlorinated-hydrocarbon content of the 

 specimens in this study was, in general terms, 

 directly related to the lipid content. The groupers, 

 which contained <1% lipid, contained the least 

 iDDT and PCB. King and Spanish mackerel had 

 the highest lipid contents, 3.5 and 4.6%, respec- 

 tively, and the highest levels of both IDDT and 

 PCB. In three of the six species, the correlation 

 between lipid and IDDT was significant, i.e., 

 P<0.05. Similarly, in three of the four species for 

 which PCB were quantifiable the correlation be- 

 tween lipid and PCB was significant. Possible rela- 

 tionships between size and chlorinated hydrocar- 

 bon content were also examined. Although length, 

 weight, iDDT, and PCB were all studied, in no 

 case was a significant correlation found in any of 

 the six species (Table 4). In two of the six species, 

 the correlations between length and lipid and also 

 between weight and lipid were significant. In both 

 species, red snapper and king mackerel, the P 

 values for lipid versus chlorinated hydrocarbon, 

 were below 0.01. Giam et al. (1974) noted a rela- 

 tionship between size and concentration of pollu- 

 tants in groupers from the Gulf of Mexico, but only 

 in the area with the highest contamination, i.e. , up 

 to 0.1 ppm. 



SDDT and PCB levels within single species 

 were compared at the various sites. Fish from the 



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