Aspects of the Natural History of Pelagic Cephalopods of the Hawaiian Mesopelagic-Boundary Region

Abstract

Pelagic cephalopods of the mesopelagic-boundary region in Hawai'i have proven difficult to sample but seem to occupy a variety of habitats within this zone. Abralia trigonura Berry inhabits the zone only as adults; A. astrosticta Berry may inhabit the inner boundary zone, and Pterygioteuthis giardi Fischer appears to be a facultative inhabitant. Three other mesopelagic species, Liocranchia reinhardti (Steenstrup), Chiroteuthis imperator Chun, and Iridoteuthis iris (Berry), are probable inhabitants; the latter two are suspected to be nonvertical migrants. The mesopelagic-boundary region also contains a variety of other pelagic cephalopods. Some are transients, common species of the mesopelagic zone in offshore waters such as Abraliopsis spp., neritic species such as Euprymna scolopes Berry, and oceanic epipelagic species such as Tremoctopus violaceus Chiaie and Argonauta argo Linnaeus. Others are apparently permanent but either epipelagic (Onychoteuthis sp. C) or demersal (Nototodarus hawaiiensis [Berry] and Haliphron atlanticus Steenstrup). Submersible observations show that Nototodarus hawaiiensis commonly "sits" on the bottom and Haliphron atlanticus broods its young in the manner of some pelagic octopods.