Argonautidae

Abstract: Large pelagic predators were used as biological samplers to gain information on cephalopod diversity, abundance, distribution, and their role as prey in the Northwest Atlantic Ocean. Fish predators were caught by recreational anglers in offshore waters of New England (NE; 2007–2010), the Mid-Atlantic Bight (MAB; 2009–2010) and the South Atlantic Bight (SAB; 2010–2011). In total, 2362 cephalopods, including 22 species of squid and 4 octopods, were identified in the diets of 13 species of predatory fishes. Cephalopod body sizes were obtained for 1973 specimens through direct measurement of mantle lengths (ML) or estimated using lower rostral/hood lengths of lower beaks. Cephalopod diversity (number of species) was highest in predator diets from the SAB ( N =19), intermediate in NE ( N =18), and lowest in the MAB ( N =9); however, differences may reflect unequal sampling effort among regions. The most important cephalopods across predator diets by number and frequency of occurrence were from the families Ommastrephidae, Argonautidae, Loliginidae, and Histioteuthidae. Shortfin squid ( Illex illecebrosus ) and paper nautilus ( Argonauta sp.) were the most recurrent species identified across spatiotemporal scales; size distributions of these two species varied significantly among regions, and the largest individuals on average were found in the MAB. Results demonstrate that although pelagic predators consumed a broad range of cephalopod species, octopods and squids from the families Argonautidae and Ommastrephidae dominated the collective diets of numerous pelagic teleosts and elasmobranchs, and play a key role in offshore food-webs of the Northwest Atlantic Ocean. This study emphasizes the value of using predators as biological samplers to gain information on cephalopod biogeography, and as a potential approach to track ecosystem changes in this region due to environmental and anthropogenic stressors.

Abstract: Early life cephalopod stages were collected around tropical seamounts and oceanic islands off the north-eastern coast of Brazil. A total of 511 specimens was caught with oblique Bongo net hauls between 150 m depth and the surface during a joint Brazilian/German oceanographic expedition with the RV VICTOR HENSEN in January/February 1995. Mean density of cephalopods was low with 24 ind 1000 m−3. Fifteen families representing at least 21 genera, from which 11 species were identified. The findings revealed a typical tropical and oceanic cephalopod assemblage. The most abundant families were Enoploteuthidae (27.6%), Ommastrephidae (20.9%), Onychoteuthidae (11.2%), Cranchiidae (10.4%) and Octopodidae (9.2%). Less abundant families were Octopoteuthidae, Thysanoteuthidae, Cthenopterygidae, Lycoteuthidae, Mastigoteuthidae, Tremoctopodidae, Argonautidae, Chiroteuthidae and Bolitaenidae. Highest cephalopod densities occurred along the Fernando de Noronha Chain (34 ind 1000 m−3). Small-sized Enoploteuthidae and Onychoteuthidae dominated in that region. Around the North Brazilian Chain overall cephalopod density was 31 ind 1000 m−3 where again, Enoploteuthidae were most abundant, closely followed by Ommastrephidae. Cephalopod abundance was the lowest (13 ind 1000 m−3) around the St. Peter and St. Paul Archipelago. However, cephalopod diversity was highest in this region (17 genera) with Enoploteuthidae dominating, followed by Cranchiidae. Cephalopod mantle lengths (ML) ranged from 0.8 mm to 25 mm. The majority of specimens were small-sized with 65% below 3 mm ML, and 81% below 4 mm ML. All major genera and species are illustrated and their meso-scale distribution patterns are discussed. The results provide new information on the species composition and distribution patterns of early life cephalopods in tropical seas.

Abstract: The relationship between the increase of the sea surface temperature observed off the Galician coast and the appearance of a tropical poikilotherm species Argonauta argo in these coasts is discussed. This is the first record of Argonauta argo in the north-west Iberian Peninsula. A female of this species was captured alive near the surface at dusk on 22 December 2000 in the Ria de Aldan (42°15'N-08°48'W). The specimen, a mature female of 70 mm mantle length and 96 mm shell diameter, died 36 hours after introduction in the tank.

Abstract: A mass stranding of A. nodosa was registered along more than 250 km of the Uruguayan coast between January and April 2004. Such unusual event was associated with singular oceanographic and meteorological conditions that advected oceanic warm waters toward the shore, reaching inside the Rio de la Plata estuary. This is the first record of a mass stranding of argonautid cephalopods in the southwestern Atlantic Ocean.