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Comparisons of the rates of growth, feeding habits and heavy metal levels of flounders from Barnstaple and Oldbury-on-Severn have shown that at all ages the fish from the North Devon coast are larger than those from the middle Severn estuary and that there are marked differences in diet. These differences in diet may contribute to the much higher zinc levels of the Barnstaple flounder samples.In the six other fish species which have been examined, there is a distinct correlation between the cadmium concentrations of the tissues and the proportion of crustaceans in the diet. Lead concentrations appear to follow a similar trend, but no relationship could be detected between diet and tissue zinc levels. 相似文献
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Tissues and organs of the flounder collected from the Severn at Oldbury, in the course of a year long survey, have been analysed for lead, cadmium and zinc. Differences have been noted in the level of zinc deposition in the various age groups of this teleost, particularly in autumn and summer. In an attempt to explain these results, the feeding habits of the flounder have been studied and heavy metal analyses conducted on some of its principal foodstuffs and related animals. 相似文献
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First year whitings, winter residents of the Severn Estuary, had highest levels of zinc in November 1975 but maximum concentrations of lead and cadmium in March 1976. These metal levels are linearly related to both the length and weight of the fish. It is suggested that zinc concentrations reach an upper threshold limit beyond which there is no further accumulation. This is quickly reached as fish move into polluted areas. 相似文献