This tracks with the historic consumption of other species that are also hosts to zoonotic nematodes raw. It's worth noting that wild salmon do have a very high natural prevalence of Anasakid roundworms.. however these aren't microscopic by any means and a sushi chef could easily screen for them.
I think it probably was just about having a consistent, abundant and standardized product rather than highly seasonal and variable wild salmon. You might not be able to beat the right word salmon in the right part of the year if you are are real connoisseur but that isn't amenable to mass consumption. The fat distribution is different as well in a farm raised salmon even if the amount was the same, large visible deposits and it has a very noticable mouth feel and flavour.
Long story short I reckon farm raised salmon took off there for the same reason it has in chain restaurants (cooked) in the US.
I think it probably was just about having a consistent, abundant and standardized product rather than highly seasonal and variable wild salmon. You might not be able to beat the right word salmon in the right part of the year if you are are real connoisseur but that isn't amenable to mass consumption. The fat distribution is different as well in a farm raised salmon even if the amount was the same, large visible deposits and it has a very noticable mouth feel and flavour.
Long story short I reckon farm raised salmon took off there for the same reason it has in chain restaurants (cooked) in the US.