Boiling a 3kg pike using a pot results in 1kg of boiled pike in the pot.
Boiling 3x 3kg pikes using a pot also results in 1kg of boiled pike in the pot.
There is no way to boil a pike without losing most of it (my character was tired of roast pike and did not have a any vegetables for pike soup so wanted to try boiled pike using the new birch bark pot).
I would expect my character to use only as much as can fit in the pot or to abort trying to boil the pike(s) since they are too big for the pot, rather than the food simply disappearing.
Probably not new but I noticed in the beta trying out the new birch bark pot.