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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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K. J. Sainsbury 《新西兰海洋与淡水研究杂志》2013,47(2):163-173
A population model is developed and used in conjunction with the results of a study of an unexploited population of paua (Haliotis iris Martyn) to examine the historical pattern of recruitment and yield per recruit. As H. iris cannot yet be aged, the population model uses size rather than age classes, but is structurally similar to the Leslie matrix model. Simulations suggest that the observed population size structure resulted from a short (about 5 year) period of high recruitment, preceded and followed by longer periods of low recruitment. Yield per recruit analysis shows that the present minimum legal size for the fishery (127 mm) provides close to the maximum yield per recruit for most stocks, although yield per recruit could be increased in some areas by a reduction in minimum legal size. 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