Abstract
Contamination of freshwater fishes with 137Cs remains as a serious problem in Japan, nearly 10 years after the Fukushima nuclear power plant accident, but there is limited information on the distribution of 137Cs contamination in fish bodies. The 137Cs distribution can be used for the estimation of internal radiation exposure through the consumption of fish and for the dose estimation of fish themselves. In this study, the 137Cs distribution in the bodies of 8 freshwater fish species was investigated as percentages of total body burden for fish inhabiting Lake Inba. Fish samples were caught in stake nets placed close to the shore approximately once a month. After the measurement of body length and fresh weight, the radioactivities of 137Cs in muscle, internal organs, spawn, milt and bone were assayed using high-purity germanium detectors. Analysis of all fish samples showed that the 137Cs distribution was highest in muscle (54 ± 12%), followed by internal organs (7.8 ± 4.6%), spawn (7.4 ± 5.4%), milt (3.2 ± 2.1%) and bone (1.2 ± 0.58%). Among fish species, the highest proportion of 137Cs in muscle was detected in largemouth bass (71 ± 1 3%), followed by snakehead (69 ± 14%), channel catfish (63 ± 17%), common carp (62 ± 14%), barbel steed (58 ± 6.5%), silver carp (57 ± 7.7%), bluegill (53 ± 4.7%), and crucian carp (50 ± 10%). These results suggested that the 137Cs in muscle was likely to be high in piscivorous fishes compared to omnivorous fishes, especially crucian carp. The proportion of 137Cs in muscle of crucian carp was not explained either by body length or fresh weight. However, a positive correlation was found between the proportion of 137Cs in muscle and the condition factor which was an indicator of nutritional status calculated from a length–weight relationship. This correlation implied that more 137Cs accumulated in muscle tissue of a fish species with high nutritional status. This is the first study to show that condition factor is more important than body length and wet weight in explaining the high proportion of 137Cs in muscle tissues, at least for crucian carp.
Highlights
Contamination of freshwater fishes with 137Cs remains as a serious problem in Japan, nearly 10 years after the Fukushima nuclear power plant accident, but there is limited information on the distribution of 137Cs contamination in fish bodies
Quantity of food intake is probably an important factor affecting the proportion of 137Cs in muscle at least for crucian carp in Lake Inba. This is the first study to document that nutritional status of fish is an important factor affecting the proportion of 137Cs in muscle tissue in addition to differences in fish species and trophic level
The 137Cs distribution within freshwater fish bodies were investigated in Lake Inba
Summary
Contamination of freshwater fishes with 137Cs remains as a serious problem in Japan, nearly 10 years after the Fukushima nuclear power plant accident, but there is limited information on the distribution of 137Cs contamination in fish bodies. This correlation implied that more 137Cs accumulated in muscle tissue of a fish species with high nutritional status This is the first study to show that condition factor is more important than body length and wet weight in explaining the high proportion of 137Cs in muscle tissues, at least for crucian carp. Fish is one of the sources of dietary protein, and the importance of inland water fisheries has globally increased[6] This raises concerns about internal exposure of humans through consumption of contaminated freshwater fish. Fish muscle tissue is selected for the measurement of radiocesium activity concentrations because of its consumption by the people[7], but a homogeneous distribution of radiocesium within a fish body is unlikely. Data on distribution of radiocesium in various tissues and organs will provide valuable information regarding dose estimation of freshwater fish species
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