Fish Bones become available after the third cooking research perk is unlocked. Consuming all any kind of fish besides shrimps will yield fish bones.
One sardine will yield 1 fish bone.
One tuna will yield 5 fish bones.
One swordfish will yield 10 fish bones.
One shark will yield 25 fish bones.
One whale will yield 100 fish bones.
Ten Fish Bones can be converted into one Bonemeal.