The smaller fry get contaminated by the food they eat, the larger fry eat them and add to the amounts they already have, the larger ones eat them and so on until you have a large fish with VERY high levels of contaminants... Same happens with mercury. I thought I remembered learning that's why the Eagle and the Osprey were so affected.
Maybe I'm remembering incorrectly?
You have it right. The higher up on the food chain, the more bad stuff gets concentrated. Big trouble for apex predators. Heavy metals and many pesticides can't be excreted. If the food has this stuff, each critter in the food chain just concentrates it. By the time you get to an eagle, swordfish, or tuna, you can have problems.
