Ya dont let a resource go to waste if you want to put the time into it.
I know Alaska is the easy cheap fish fertilizer available, but many people dont know that it is not a whole fish product. It is a by-product of fish oil harvesting that oil that is being stripped out carries a ton of nutrients for plants just as it does for people. Neptunes Harvest is cold processed and they don't strip any oil off of it.
A couple years ago I seriously considered and investigated making fish fertilizer commercially, came up with a recipe, had it laboratory tested, but I decided not to take the big dive on the venture.
A consideration should also be made in concern to the amount of heavy metals growers are applying to their grow beds with heavy use of fish fertilizer. I've seen many voice concerns about micro plastics in different threads but this is the same or greater health consideration. A heavy metal report can be had by contacting the producers.