> it looks like the salmon needs to be above 63C for 15 seconds to kill the bacteria

I guess if you like overcooked salmon.

Food safe temperatures aren't a hard line. Bacteria die off at much lower temperatures than 65ºC (from around 54ºC). What does change with temperature is the rate at which bacteria die. The usual safety goal is to get a 6.5 log10 reduction in bacteria.

The reason that 65ºC is usually chosen as a safe temperature is because once you reach that temperature the time to reach that reduction is very short (about 1.5minutes), at 70ºC it's instantaneous.

At lower temperatures, you have to keep the food at that temperature for a longer amount of time (there are reference charts to be found online[1]). For this to be safe you have to be able to measure and/or control the temperature reliably. This is obviously more difficult to do than just cooking to a specific temperature. In many commercial applications it's just easier to cook to a high enough temperature to not have to worry about it.

There are also other ways to kill the bacteria. I usually cure salmon overnight in the fridge (2:1 ratio brown sugar and salt) before smoking it to 54ºC. The temperature doesn't kill the bacteria but the curing does.

[1] https://www.fsis.usda.gov/sites/default/files/media_file/202...

Yeah it's tricky isn't it, I guess if you're cooking with a new kitchen tool, in this case a dishwasher, I think it's reasonable to say it may take little while to figure out that exact combo of safe and perfectly cooked. I think my recommendation to you would be when you're cooking in the dishwasher err on the side of safety. The maybe experiment from there, perhaps a lemon dishwasher tablet would add a zing.

Thanks for the detailed answer; it's important to understand temperature vs time. I presume you sometimes sous vide fish?