Cephalopoda
Collection

Methods of capture of planktonic life stages of cephalopods do not differ from those recommended for fish larvae and juveniles. It is best to tow nets at low ship speeds. Vertical plankton tows are not recommended because the low volumes of water usually filtered normally result in only very small numbers of larvae, and fail to capture even the juveniles of actively swimming cephalopods in sufficient quantities. For larvae, the Bongo net or its various analogues may be recommended. Juvenile stages of active nektonic squids, and almost all stages of semiplanktonic squids and pelagic planktonic octopuses, may be caught by various midwater trawls, such as the Isaacs-Kidd Midwater Trawl (IKMT) and similar nets. Fine-meshed nets (5 or 10 mm knot-to-knot) should be inserted either in the cod-end or, in some types of IKMT, along the whole length of the trawl. For subadult and adult pelagic cephalopods the best devices are large commercial pelagic otter-trawls (or pelagic versions of bottom otter-trawls) with a fine-meshed section at the cod-end. When using fine-meshed nets in a commercial trawl, permission from the local fish protection agency should be requested.

For better preservation and easier subsequent identifications, immediate sorting of the catch prior to fixation is recommended, although this is rarely possible when dealing with standard plankton catches.