system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes "Sushi Grade Fish" safe for consumption as apposed to normal raw fish?

I've recently gotten into cooking and making meals, and I quite like sushi, so it'd be nice to know what exactly distinguishes the two from each other. I'm not asking how do I get sushi grade fish, I will only eat raw it if I'm informed the fish is Sushi Grade. I'm more asking how the science, biology, chemistry, etc. behind it works, and how Sushi Grade fish is procured and produced in comparison to normal fish.
gpt
Sushi is made from salt water fish (ocean fish) vs fresh water fish (river or lake fish). Ocean fish naturally has less parasites and bacterial content so it's safer to eat raw. Fresh water fish needs to be cooked.

Fish like Tuna is fresh caught, bled immediately, and chilled to make it safe to eat. Tuna and other fish shipped to North America is packed in ice for the trip.

Many other fish like Salmon which are more prone to parasites are flash frozen to kill any parasites while retaining it's texture and taste when thawed.

The simple answer is that the fish isn't necessarily *raw* it's flash frozen to kill anything bad for you.