Fishy figures at Fukushima

Wednesday, 22 August 2012

Sampling of aquatic animals near the Fukushima Daiichi site has revealed various levels of contamination - and focused attention on one outlying result.

Two small fish from one location gave extraordinary results

Tokyo Electric Power Company took 50 samples of a range of species off the coast of Fukushima prefecture within 20 kilometres of the wrecked nuclear power plant. Several of the samples returned concentrations of radioactive caesium-134 and -137 in excess of government regulations for food (100 becquerels per kilogram, bq/kg).

No fishing boats are allowed in the area where these samples were taken, within 5 kilometres of the coast, by virtue of the evacuation orders in force since 11 March last year. Commercial fishing is strictly monitored by government agencies.

Of the 24 samples above the limits for human consumption, 16 were between 100 and 250 bq/kg, with six above 300 bq/kg and two in the range 400-500 bq/kg. One sample result, however, showed fifty times this level of contamination at 25,800 bq/kg.

This outlying result related to two greenlings - small bottom-feeding fish measuring 5 cm in length - that were caught 1 kilometre offshore near the Ota River. The contamination results for these two small individuals were scaled up to give a result in bq/kg that could be compared to results from larger species.

Two other greenling catches from different places showed 213 and 223 bq/kg, which remains above the government's 100 bq/kg limit but within the range of the rest of the data.

Tepco presented all the figures on its website but offered no comment on the extraordinary result.

Researched and written
by World Nuclear News