TEPCO announced (link in Japanese) on February 28, 2013 that a greenling caught inside the harbor of Fukushima I Nuclear Power Plant on February 17, 2013 was found with 510,000 becquerels/kg of radioactive cesium, highest ever tested in fish since the start of the nuclear accident.
Cesium-134: 180,000 becquerels/kg
Cesium-137: 330,000 becquerels/kg
In January 2013, a spotbelly rockfish inside the harbor was found with 254,000 becquerels/kg of cesium.
A Pacific cod, caught in the same location as the 510,000 Bq/kg greenling (near the harbor mouth), had only 130 becquerels/kg of radioactive cesium. Greenling is a bottom-dweller, while Pacific cod isn't.