Distribution of cephalopods from plankton surveys around the British Isles

Cephalopods (n = 515) were identified from a series of plankton and fine meshed midwater trawls, taken between 1977 and 1999, around the British Isles. The collections were not directed at cephalopods, but provide valuable information on the distribution of planktonic species and on the paralarvae of the benthic species. The most abundant species in neritic areas were the octopod Eledone cirrhosa and the sepiolids, Sepietta oweniana and Sepiola atlantica. Eledone cirrhosa were common in samples to the north and west of Scotland, particularly in early summer. The mantle lengths of E. cirrhosa were 4-8 mm, indicating a brief planktonic existence or, perhaps, net avoidance by larger specimens. In the shelf-break collections from the west of Scotland and Ireland the squids Brachioteuthis spp., Gonatus sp., Teuthowenia megalops and rynchoteuthions of the Ommastrephidae were abundant. Two types of rhynchoteuthion were found and were probably Todarodes sagittatus, Illex coindetii or Todaropsis eblanae. Despite the abundance of Loligo forbesi around the British Isles, it was rarely taken in plankton collections, probably indicating that it does not have a planktonic paralarva.