I don' t think they ever changed something for me.
I think the good hint are sea VEGETABLES, not exactly animals (even if they are rich in zinc, they are also rich in heavy metals... as any animal meat accumulate heavy metals much more than plants due to bio accumulation).
These sea vegetables hold heavy metal binding properties, they are extremely rich in bio available iodine, and feel very grounding when eaten regularly, every day.
Even if they actually have heavy metals too (in less concentration than fish), I consume them regularly and I think this is one of the things that make me feel grounded, less anxious.
Anthony William recommends Atlantic sea vegetables. Any sea weed. He said that the biological function of sea weeds is to clean the oceans from heavy metals and other toxins. They hold these heavy metals and render them bio-INACTIVE for other sea lives.
Of the ones you mentions I only eat shrimp and sardines. But only small amounts of shrimps and not much of sardines either. But don't belive they should be a problem if not eaten in excess. If you know their origin - not from a dumping area etc - they should be fine.
Oysters may be toxicated by algae some sometimes in the season at some places so one have to check.