They were making feed for hatchlings in NZ, the mercury levels in NZ fishmeal were considered to be too high.  Protein content was too low from NZ fishmeal from waste.  IIRC the company making it was Salmon Services.

The amount of mercury in the diet is reduced now that salmon diet is using mainly vegetable protein, so higher levels in the base fishmeal can probably be got away with.

There have been concerns about mercury in NZ fishmeal used for pig food.

Natural astaxanthin is used in some finished food products - it's expensive.  Wild salmon is seldom the deep colour of farmed salmon.