[Nyororin]

Radiation itself moves poorly through water -this is why the spent fuel rods were submerged in water. So many meters of it virtually removes the risk.

There will doubtlessly be some fish that are contaminated... But I really don`t think that there needs to be much worry.

Why?
Because the fish from that direct area aren`t going to be safe to eat ANYWAY because of all the stuff that was washed into the sea by the tsunami. I`d be much much more concerned about almost definite chemical contamination than trace radiation. Both would effect the exact same area, but the radiation is an "if" - the chemicals are a definite.