The short answer is no. You would need to subject them to a spectrum analyzer to see exactly what elements are there.
The problem is that starting at the level of the microorganisms they are filter feeders so they are consuming and accumulating things like heavy metals. Those organisms are then eaten by the next level on the food chain with each higher predator accumulating higher and higher levels of contaminates.
Because of this it really doesn't matter much where the fish come from as their prey came up the ladder over the wider area. Not quite so true of shellfish since they are base filter feeders but as our oceans become more and more polluted this is only getting worse with time.
Last week there was a story online about a yacht racer who talked about the appalling degradation of the Pacific Ocean between today and the last time he had run the exact same course ten years ago. He said the ocean was practically dead, where ten years ago he could drop a line and be sure of catching his dinner every day on this trip he caught a total of 2 fish. The ocean was so filled with trash he couldn't run at night for fear of hitting something big enough to endanger his boat. He couldn't use the engine when the wind was down because he would foul the propeller in no time. Considering that he sailed completely across the Pacific this is a frightening story.
Before the Japanese tsunami there was a sea of buoyant trash the size of Texas trapped in the Pacific and an equal one in the Atlantic. Now added to this is all of the debris from Japan which is a massive amount.
Sadly we are killing the oceans of the world first by rampant overfishing and secondly by out of control pollution.
Our seafood is becoming more and more contaminated every day. It is unwise to consume large amounts of any seafood these days.