In January 1996, large numbers of cuttle bones of different sizes (from 30-40 mm to 200+ mm in length) were washed ashore on beaches throughout Northeast Scotland and as far North as Shetland. Cuttle bones are the internal skeleton of cuttlefish (Sepia spp.) and help to maintain the animal's buoyancy. Judging from the shape of the cuttlebones, these probably came from Sepia officinalis (see Fauna Iberica, vol. 1 Cephalopoda, by A. Guerra). The largest of the cuttlebones in the picture is 21 cm in length.
Cuttlefish are common in the English Channel, where they are fished by English and French boats, but are usually seen only in small numbers in Scottish waters. They are, however, recorded as showing periodic mass invasions of northern waters, probably related to the occurrence of particular (and unusual) oceanographic conditions.
Like almost all cephalopods, they are short-lived (up to 2 years) and die after breeding. They mature at a wide range of body sizes: Sepia officinalis can reach sexual maturity at a mantle length of 6-8 cm but some grow to 20 cm or more. The main breeding season is in the summer but there is also spawning in the winter. It is thus possible that the cuttle bones washed ashore are from a post-spawning die-off although, because they are buoyant, they could have been carried here from a long distance away.