TOKYO (AP) — Radioactive cesium levels in most kinds of fish caught off the coast of Fukushima haven’t declined in the year following Japan’s nuclear disaster, a signal that the seafloor or leakage from the damaged reactors must be continuing to contaminate the waters — possibly threatening fisheries for decades, a researcher says.

Though the vast majority of fish tested off Japan’s northeast coast remain below recently tightened limits of cesium-134 and cesium-137 in food consumption, Japanese government data shows that 40 percent of bottom-dwelling fish such as cod, flounder and halibut are above the limit, Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution in Massachusetts, wrote in an article published Thursday in the journal Science.