Your recipe calls for "Sushi Quality" fish, what the heck is that? I'm sous viding the fish, not eating it raw so what does sushi have to do with it?
Many sous vide fish recipes specify using "high quality" or "sushi quality" fish. While it's always good to use higher quality ingredients, it is important from a safety standpoint for lower-temperature fish recipes (anything cooked below 130°F to 140°F (54.4°C to 60.0°C).
Without going into too many details, many different pathogens can be present in different fish, based on the type of fish, how and where it was caught, and how and where it was stored. Certain fish are designed to be eaten raw as sushi or sashimi, or cooked to only low temperatures, while other fish are assumed they will be cooked to higher temperatures.
When planning to cook fish to a low temperature, whether this is using sous vide or traditional methods, you want to pick fish that you would feel safe eating raw. The low temperatures used in the cooking process will not kill all the pathogens that might be present, so it's important to use fish that are already safe to eat.
This is similar to picking beef to use for hamburgers, or especially beef tartare. Because the inside of hamburgers usually doesn't become fully cooked (unless cooking to well-done) you need to use higher quality, "cleaner" beef than if you were just grilling or searing it, knowing that the high temperatures would kill any pathogens.
This safety issue regarding low-temperature fish has really become more widespread through the use of sous vide, but it has always been present whenever fish has been cooked to rare or medium rare. Many people were not aware of the potential hazards of not fully cooking their fish, especially if the fish isn't high quality.
I hope this helps out. Thanks and happy cooking!
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