Fish assemblages inhabiting a complex of south Tyrrhenian seamounts and banks were characterized using a remotely operated vehicle (ROV). Fish distribution was assessed through surveying 15 ROV transects. Video segments of each transect were split into two bathymetric ranges, above and below 200 m depth. In total 28 fish taxa belonging to 22 families were recorded. The number of species observed at the Marettimo Banks and the Aceste Seamount was higher compared with the Tiberio and Scuso Seamounts. The number of species recorded in the shallow part (<200 m depth) of the Marettimo Banks and the Aceste Seamount was higher than in the deeper zone (>200 m). Assemblages were numerically dominated by Anthias anthias, Callanthias ruber and Helicolenus dactylopterus. The occurrence of some elasmobranchs of conservation concern, such as Squatina aculeata, Hexanchus griseus, Squalus blainville and Galeus melastomus, was noteworthy. Differences in fish assemblage composition were observed between the Aceste Seamount and the other sites and especially between the two bathymetric ranges. The fish distribution pattern showed significant relationships with bottom slope and some substrate types. A large occurrence of lost fishing gear characterized the sites closest to the coast (the Marettimo Banks and the Scuso Seamount), providing, along with scanty observations of commercially important fishes, evidence of heavy fishing activities. The adoption of conservation and management actions in the investigated seamounts and banks, such as their inclusion in the Natura 2000 network, would be very helpful to protect some threatened elasmobranchs and restore valuable deep-sea habitats.

Oceanic islands and seamounts are considered biodiversity hotspots. Here, we present a taxonomy and community analyses of hyperiid amphipods collected near oceanic islands and over seamounts of the Juan Fernández Archipelago and Desventuradas Archipelago in the South-east Pacific. Both archipelagos are separated by about 800 km over the meridional gradient, suggesting the existence of different hyperiid communities because of apparent geographic isolation and distinctive oceanographic characteristics between regions. To test this hypothesis, zooplankton samples were collected from 19 stations during the CIMAR 22 ‘Oceanic Island’ cruise in October–November 2016. In total, 56 species of hyperiids were found, of which Phrosina semilunata, Lestrigonus schizogeneios, Hyperietta stephenseni, Hyperioides longipes, Phronimella elongata and Primno latreillei were the most abundant and recurrent species. The species richness (S), Shannon–Wiener diversity (H’) and dominance (D) of both the archipelagos were not significantly different. Additionally, except for a small group of rare species, the species composition was similar in both areas. Most species showed greater abundances than those observed in the coastal upwelling zone off Chile, whereas shared species between regions suggested the presence of a single biogeographic unit comprising the coastal transition zone and oceanic area off Chile within which both archipelagos are included. Correlation analysis indicated that salinity was the best predictor for the community structure, which provides evidence that the contributions of previously described water masses of the South-east Pacific may influence the spatial distribution and composition of the hyperiid community.

The aim of the present investigation is a thorough inventory of the Harpacticoida (Copepoda) of the Portuguese islands Madeira and Porto Santo to provide a basis for comparisons of the harpacticoid faunas of successive elevations of the so called ‘Madeira Hot Spot Track’. Quantitative samples from 10 sampling locations at the coastlines of both islands were analysed (eight from Madeira and two from Porto Santo) and revealed a total of 27 families of Harpacticoida. Nine of the families were determined on species level comprising 43 species of which 31 were new to science. Comparisons of the family and species assemblages at the different Madeiran sampling locations indicate strong habitat heterogeneity as well as differences of the southern from all remaining locations. The sampling locations at the north and east coast are predominately characterized by interstitial taxa, those of the south coast by more robust burrowing or epibenthic taxa. Furthermore the two easternmost sampling locations of Madeira show clear similarity in terms of their harpacticoid assemblages with the sampling locations of Porto Santo. Eighty-eight per cent of the determined species of Porto Santo occur at the coast of Madeira as well (predominately at the easternmost sampling locations) indicating dispersal of Harpacticoida between both islands.

Spatial distribution patterns of microzooplankton (0.055–0.3 mm) biomass and abundance were studied in relation to the hydrographic situation and the local flow field in the waters off Ampère and Senghor, two shallow seamounts in the subtropical and tropical NE Atlantic, in comparison with unaffected open ocean reference sites. Ampère was sampled during November/December 2010 and Senghor during December 2011 and February 2013. The study includes taxonomic composition, abundance of meroplanktonic larvae and an estimation of the respiratory carbon demand. Biomass (dry weight) standing stocks of microzooplankton in the upper 100 m ranged between 30–120 mg m−2 over Ampère and 140–260 mg m−2 over Senghor Seamount, corresponding to 33 and 24% of the total zooplankton (0.055–20 mm). Highest total abundance was always found in the upper 50 m with numbers of 1070–5060 Ind m−3 at Ampère and 5050–20,000 Ind m−3 at Senghor with microzooplankton contributing 70–95%. Zooplankton accumulated mainly at the thermocline coincident with the deep fluorescence maximum and was ascertained by food supply rather than by oxygen limitation. The microzooplankton contribution to the total respiratory carbon demand was ~50% in the subtropical waters off Ampère and ~30% at Senghor, reflecting the important role of microzooplankton in the waters of the NE Atlantic subtropical gyre. Clear evidence of local seamount effects resulting in enhanced microzooplankton biomass compared with the unaffected reference sites were not detected. However, we confirmed Senghor as a hotspot for meroplanktonic larvae, suggesting a retention potential that results in significantly enhanced larval abundance in the seamount waters as compared with the open ocean.

Six new species of Hexactinellida are described from hard bottom communities of shelf, canyon and seamounts of the west coast of North America: Washington, British Columbia and Gulf of Alaska. They were collected by a variety of methods, trawl, manned submersible, and robot submersible, and hence vary greatly in condition. The six species comprise additions to five different families of the subclass Hexasterophora, Farreidae (Farrea omniclavata sp. nov. and F. truncata sp. nov.), Euretidae (Chonelasma oreia sp. nov.), Euplectellidae (Amphidiscella lecus sp. nov.), Leucopsacidae (Oopsacas olympicus sp. nov.) and Rossellidae (Acanthascus malacus sp. nov.). These additions represent an increase of 29% to the known species of Hexactinellida in this area. A completely unique form of defended tabulate stalk is described for A. lecus. The species Chauoplectella spinifera is transferred to Oopsacas.

The study focuses on the question, how a seamount in the oligotrophic eastern Mediterranean affects the zooplankton community, as compared to the open water. Zooplankton samples were taken with 333 µm nets at two sites, the Rhodes Basin and the Anaximenes Mountain, in December 2006. The samples were sieved into size fractions, and the composition, biomass, abundance and stable isotope signatures were analysed. In general, biomass and abundance of zooplankton were low, reflecting the oligotrophic character of the eastern Mediterranean, but zooplankton standing stocks were higher at the Rhodes Basin than at the Anaximenes Mountain. Stable isotope signatures showed, at a generally low level, enrichment in zooplankton taxa along the food chain within the different pelagic zones and from the surface to the deep-sea, but no significant differences between Rhodes Basin and the seamount were evident in the food web structure. The zooplankton community in the Anaximenes Mountain region in the northern Levantine Basin seems not to be influenced by a local seamount effect, despite the difference in standing stocks between the seamount and the Rhodes Basin. This seems to be driven by larger-scale upwelling and downwelling structures of cyclones and anticyclones, dominating the circulation in the area.

This work focuses on the species associations of the Baronie Seamount (north-eastern Sardinia, Italy), according to variations in depth and time of day. The aim was to highlight the potential vertical movements of the species and to compare these results to existing data from a submarine canyon. Twenty-two samples were taken at different depths and times along two trawl lines over the seamount. A total of 94 species were caught; among these, 48 bony fish, 9 cartilaginous fish, 13 molluscs and 24 crustaceans were selected for analysis. Cluster analysis showed 3 groups in which both depth and time of day play an important role in grouping. Nine species showed some daily and nocturnal movement, probably linked to trophic requirements. The daily movements according to size and sex of the shrimps Aristaeomorpha foliacea and Aristeus antennatus were also studied. For these two populations, the analysis showed an uneven distribution and the diel cycle appears to involve only the females. These species seem to adapt their life cycle to the geomorphology of the sea bottom. The diurnal movements from the base of the seamount to the edge of the continental shelf increase the range of the species distribution. In fact, the seamount, due to its geomorphological conformation, offers these species the opportunity to very quickly span a considerable range of depths. These movements are known to occur in the continental shelf and slope, but in the seamount they are broadened and can be studied more easily.

Yellowfin and bigeye tunas (Thunnus albacores and Thunnus obesus) were tagged and released between August 1995 and December 1997 at Cross Seamount and NOAA weather buoys about 200 Nmi south of Honolulu. The release and recapture data were stratified into five sites, and a bulk transfer model was used to estimate natural mortality, fishing mortality and transfer rates between the five sites. Bigeye are much more persistent at Cross seamount and less vulnerable to the fishery than yellowfin. Fishing accounts for about 5 % of the total mortality of both bigeye and yellowfin at Cross Seamount. Yellowfin are a major component of catches at inshore FADs in Hawaii. The rate of immigration from Cross Seamount to the inshore FADs is very low for both species. The fishing mortality at Cross seamount is substantial but is not adversely impacting the populations either at Cross or the inshore FADs.

In Hawaii, a variety of small- and medium-scale pelagic fisheries target fishing effort on a network of coastal moored FADs, natural inshore tuna aggregation points, offshore seamounts and offshore weather monitoring buoys. Large-scale longline vessels also operate in the Hawaii exclusive economic zone (EEZ) and beyond. These circumstances provide an ideal setting for tag-and-release experiments designed to elucidate the movement patterns, residence times, exchange rates and vulnerability of bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) within the Hawaiian EEZ. Preliminary recapture data indicate that FADs, island reef ledges and seamounts exert an overwhelming influence on the catchability of tuna. Recapture rates from these locations vastly outweigh tag returns from open water areas. As of August 31, 1999, a total of l5387 bigeye and, yellowfin tuna ranging in size from 29 to 133 cm fork length (FL) and from 26 to143 cm FL respectively (mean 59.8 ± 14.1 cm; 58.4 ± 17.3 cm) have been tagged and released throughout the Hawaii EEZ. Recapture rates for both species have been similar with an overall recapture rate of l0.3 %. The location of tag releases reflects the importance of associative behavior and schooling to the vulnerability of tuna; seamounts and FADs accounted for 72.4 % and 23.5 % of all tag releases. Within the main Hawaiian Island group (excluding the offshore seamounts and buoys), 83.1 % of all recaptures have been made on anchored FADs and 11.9 % of recaptures have come from ledges or tuna aggregation areas close to the islands where bigeye and yellowfin tuna become vulnerable to hook and line gear. As these studies continue, additional and longer-term recaptures will provide increasingly detailed information on the movement patterns and vulnerability of bigeye and yellowfin tuna as they grow, move and recruit to different fisheries.