People repeat this thing about satiation but it's not really true. In fact, the most highly satiating food is potatoes. Fish is quite high up there, but other "protein" foods like meat, eggs and cheese are nowhere near the top. Oats and many fruits like apples are higher.
The really stupid thing about fad diets like keto is you either just start craving carbs because food is miserable without them, or you develop an eating disorder. The only thing anyone should do is eat normal, delicious, home-cooked food made from mostly plants.
I got curious about this and found a lot of people in older threads saying that farming sardines can't be done. Apparently small schooling fish are typically very difficult to farm because they're pretty fragile and easily stressed.
Whether that's a technical barrier imposed by the biology of sardines being unsuited for how we do fish farming today, or more of a barrier of "it will never make financial sense to do this because so many in each batch would die" I don't know.
People will believe anything.