Towards the end of a massive Wikipedia session (I started at the “Battle of Antietam”), I saw a rather colorful image of how mercury (methylmercury) goes from the land/air into the oceanic food chain. It made me want to re-read some online posts a year or so back where the OPs and comments were discussing that eating too much sushi (generalized as the raw fish kind), or even sushi at all, results in mercury poisoning. Further research even revealed an actor whose sushi habit got him in trouble with the toxic affliction causing him to being released from a theater project (though, the real reason is in dispute).
Thinking about this from personal experience and as a Japanese resident, I have to personally dispute a few of the concerns and precautions found online. Sashimi and sushi is not only a part of Japanese culture, but the “fastfood-ification” of sushi (kaitenzushi, tachizushi, etc) probably brings people into contact with raw fish more often than what is deemed safe in the west. If so, then why aren’t there public announcements at sushi bars warning you to stop being so Japanese and give sushi a rest?
Many sources will tell you to cut back on your sushi dining frequency, portions, or lay off of it altogether. They might be overreacting or simply going by the books according to fish caught in the west. They obviously didn’t watch the Japanese TV show that featured a comedy duo polish off more maguro (raw and cooked) than most people will eat in a lifetime and in such a short time that would surprise doctors and nutritionists alike. They’re both well and still making people laugh.