If those bits were removed in homes they are almost always going to be wasted without municipal composting, and even that is still wasteful. If they are removed at scale (no pun intended) there is a much higher likelihood that they will be used as a byproduct in pet food or fertilizer or something.

I'm talking about the skins, heads and tails of fish that have no business being removed because they're edible and nutritious. I think you 're talking about the guts, that are almost always thrown out anyway.

Food waste starts with cultural norms that make some foods taboo, essentially. Like for example "offal" as the perfectly edible entrails of ruminants are derogatorily known.

In 1953 I seriously doubt there was so much concern about it, much less in an advertisment directed to consumers.

Note the oxymoron in that advert: "Fresh Frozen!".

That's not an oxymoron. It means they were frozen right away after being caught. A similar term today used especially for things like shrimp is "Individual Quick Frozen" or IQF. Shrimp are frozen on the boat that catches them.

Do you think anyone ever freezes food when it's already unfit for consumption? "Fresh frozen" is nothing more than marketing speak.

There is a pretty wide span of time between catch and "unfit for consumption."

This particular product may be totally lying about how fresh they froze their fish, but it's still not an oxymoron.