[fencepost]

Sushi-grade tuna and I suspect tuna steaks are much more likely to be from the larger tuna species. At the very high end you get the special cases where truly massive fish are sold at auction for absurd prices - the same fish that got to that size by eating a huge number of smaller fish and thus concentrating mercury. Canned "solid" albacore or "white" tuna has the same issue, though I wouldn't be surprised if it was still lower than fish sold for sushi or steaks.

Chunk "light" tuna on the other hand tends to come from smaller species and pretty much as a direct consequence has lower mercury levels.

Based on the numbers in https://en.wikipedia.org/wiki/Mercury_in_fish, canned light tuna and skipjack have 1/3 to 1/2 the mercury found in albacore and yellowfin tuna and 1/4 the levels found in bigeye. Notably, those 3 all run 2-10x the size of the smaller species used in "chunk light."