[pvaldes]

> the ones I have seen have been tiny

I may help here. As expected, the big ones are from adults in the cuttlefish fished commercially: Sepia officinalis in Europe. Around 1-2Kg or so.

But the tiny bones are (most probably) also from adult cuttlefishes. There are several species of cuttlefishes in Europe. Like Sepia elegans that is locally frequent in the Mediterranean or Atlantic but only grows 8 cm in mantle.

What you have seen is just a reflect of different phases on the ecosystem, the seasons, or the fishing techniques. After reproductive season or big storms a number of cuttlefish bones will strand all at the same time when the animals will die in mass.