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Globally, commercial fisheries have had a strong impact on elasmobranch populations directly through high catch rates and indirectly through bycatch. Consequently, the abundance of many species is declining to the extent that some are considered under threat of extinction. Regionally, this negative trend is also evident in the international waters of the southern Grand Banks (off the coast of Newfoundland, Canada), where the occurrence of the thorny skate (Amblyraja radiata) has declined by nearly 70% in recent decades. This study used Bayesian species distribution models to investigate the habitat preference and biomass trends of the thorny skate during a 14-year period (2003–2017), linking five environmental predictors (i.e., bathymetry, sea bottom temperature, seabed aspect, slope, and rugosity) and prey distribution with fishery-independent data. Our findings identify some of the sensitive habitats for this species and the ecological factors that may be driving its population dynamics in the area. We argue that knowledge about the factors influencing the distribution of this species and spatiotemporal effects could be exploited as potential mitigation measures for future fishery management strategies.

According to current systematics, the genus Halargyreus Günther, 1862 is composed of a single valid, widely distributed species, called H. johnsonii Günther, 1862, although DNA barcoding has previously suggested that specimens from New Zealand and Tasmania may belong to a different species. This research doubles the number of DNA barcodes of this species available in public repositories and expands the locations of the catches thereby allowing a better estimation of its intraspecific variability. A cladistic analysis of haplotype associations shows two independent clusters that could represent different species. These groupings overlap geographically in the North Atlantic Ocean, discarding the possibility of allopatry as previously proposed for the sequences from New Zealand and Tasmania. Similarly, none of the clusters could be assigned to H. johnsonii taking into account that the holotype comes precisely from the North Atlantic Ocean. Sequences from New Zealand and Tasmania are hierarchically linked to sequences from the North Atlantic, whereas other sequences from the South Seas, together with sequences from the North Atlantic and Pacific, form an independent group with no hierarchical link to the former. These preliminary results indicate not only the need to delve deeper into the systematics of the genus Halargyreus, but also suggest the existence of a complex of cryptic species of which an attempt should be made to clarify using the combined traditional and molecular taxonomies.

The new information reported in this paper is based on 11 specimens of the large-tuberculate octopus Graneledone macrotyla . These specimens were caught in bottom trawl surveys ATLANTIS 2009 and 2010 carried out on the Patagonian slope off the Argentinean Economic Exclusive Zone between 24 February and 1 April 2009 and from 9 March to 5 April 2010 respectively. A new diagnosis and a complete description of the species are provided. This is the first time that stylets, beaks and spermatophores are described. This is also the first time in which mature females have been studied and the female genitalia described. Like other eledonid octopods, G. macrotyla does not have spermathecae in the oviducal glands. The presence of fertilized eggs inside the ovary suggests that fertilization takes place within the ovary. The simultaneous occurrence of oocyte cohorts at different oogenic stages suggests that the species is a multiple spawner. G. macrotyla inhabits shallower waters on the Patagonian slope (475-921 m) than in the subantartic area (1647-2044 m). From a biogeographical point of view, our data show that G. macrotyla inhabits the plume of cold subantarctic waters, which is pushed far north into the southwestern Atlantic by the Falkland (Malvinas) Current.

8 pages, 3 figures, 5 tables, The stomach contents of three squids: 57 Doryteuthis gahi with mantle length (ML) ranging from 7.0 to 37.0. cm, 75 Illex argentinus (21.0-32.8. cm) and 116 Onykia ingens (19.9-39.3. cm) from commercial catches on the outer Patagonian shelf grounds during autumn (March and April 2012) were examined to describe their diet and compare their trophic spectrum. D. gahi preyed on 12 different items, I. argentinus on 20 and O. ingens on 29. Prey diversity increased with the sizes of the squids. Along growth, D. gahi shifted from crustaceans, mainly euphausiids to fish (Salilota australis) and squid (D. gahi and Histioteuthis sp.). Small to mid-sized I. argentinus and O. ingens consumed mostly two fish, two squid species D. gahi and Histioteuthis atlantica, two crustaceans Munida gregaria and Munida subrugosa and the Chaetognatha Sagitta elegans. All the three species show a high prey overlapping at similar sizes: Squid of smaller size (5-15. cm ML) fed mainly on crustaceans: D. gahi on euphausiids and squat lobsters (Munididae). Mid-sized squid fed mainly on fish, most frequently Gymnoscopelus sp. and S. australis, and larger I. argentinus and O. ingens fed mostly on squids, including cannibalism. The overlapping of the diet of similar sized squid was large suggesting all preys are abundant species in autumn in the water column in the Patagonian Shelf. © 2013 Elsevier B.V., Rigoberto Rosas Luis was supported by CONACyT (Con-sejo Nacional de Ciencia y Tecnología, México)

10 páginas, 7 figuras, 2 tablas, The new information reported in this paper is based on five maturing and mature females of the large-tuberculate octopus Graneledone macrotyla. These specimens were caught in bottom trawl surveys ATLANTIS 2009 (February 24 to April 1, 2009) and ATLANTIS 2010 (March 9 to April 5, 2010) carried out off the Argentinean Economic Exclusive Zone. Capture depth ranged from 475 to 921 m and sea bottom temperature between 2.8 and 3.1 °C. Development of the complex ovary, oviducts, and oviducal glands during gonadic maturation is described. The absence of spermathecae in the oviducal glands and the presence of fertilized eggs inside the ovary suggested that fertilization took place within the ovary. Histological techniques showed the presence of four types of oocytes. Maturing oocyte size–frequency distribution was polymodal. Fluorescence reaction showed that atresia occurred in both early and later oocyte maturation stages. Atresia affected 48–55 % of the initial number of oocytes. The maximum observed potential fecundity was estimated at 250–300 eggs. G. macrotyla showed a group-synchronous ovulation pattern, regulative atresia, and a batching spawning pattern with a few egg batches spawned intermittently over an extended period of spawning.

Ninety cephalopod specimens were collected in 71 of the 132 hauls (54%) during the bottom trawl survey ATLANTIS 2009 undertaken between 24 February and 1 April 2009. The surveyed area was the zone between parallels 44° and 48° South, east of the Argentinean Exclusive Economic Zone down to the 1500 m depth contour on the high seas of the Southwest Atlantic. The collection was composed of 16 species of squids and 5 of octopods. The best represented groups were Histioteuthidae (5 species) and Octopodidae (5). The most abundant species were Gonatus antarcticus (25.5%), Histioteuthis atlantica (11.1%), and Muusoctopus eureka (8.9%), which were also the most widely encountered. The geographic and/or bathymetric distribution ranges of 9 species are extended, and this is the first record of Galiteuthis glacialis outside circumpolar Antarctic waters. Our data show that several species, mainly of octopuses, penetrate the area studied as the plume of cold sub-Antarctic waters is pushed far into the Southwestern Atlantic by the Falkland (Malvinas) Current.