Warming shelf seas drive the subtropicalization of European pelagic fish communities

Pelagic fishes are among the most ecologically and economically important fish species in European seas. In principle, these pelagic fishes have potential to demonstrate rapid abundance and distribution shifts in response to climatic variability due to their high adult motility, planktonic larval stages, and low dependence on benthic habitat for food or shelter during their life histories. Here, we provide evidence of substantial climate‐driven changes to the structure of pelagic fish communities in European shelf seas. We investigated the patterns of species‐level change using catch records from 57 870 fisheries‐independent survey trawls from across European continental shelf region between 1965 and 2012. We analysed changes in the distribution and rate of occurrence of the six most common species, and observed a strong subtropicalization of the North Sea and Baltic Sea assemblages. These areas have shifted away from cold‐water assemblages typically characterized by Atlantic herring and European sprat from the 1960s to 1980s, to warmer‐water assemblages including Atlantic mackerel, Atlantic horse mackerel, European pilchard and European anchovy from the 1990s onwards. We next investigated if warming sea temperatures have forced these changes using temporally comprehensive data from the North Sea region. Our models indicated the primary driver of change in these species has been sea surface temperatures in all cases. Together, these analyses highlight how individual species responses have combined to result in a dramatic subtropicalization of the pelagic fish assemblage of the European continental shelf.     

Seamounts: centres of endemism or species richness for ophiuroids?

Aim To test the hypotheses that seamounts exhibit high rates of endemism and/or species richness compared to surrounding areas of the continental slope and oceanic ridges. Location The south‐west Pacific Ocean from 19–57° S to 143–171° E. Methods Presence/absence museum data were compiled for seamount and non‐seamount areas at depths between 100 and 1500 m for the Ophiuroidea (brittle‐stars), an abundant and speciose group of benthic invertebrates. Large‐scale biogeographical gradients were examined through multivariate analyses at two spatial scales, at the scale of seamounts (< 1° of latitude/longitude) and regions (5–9°). The robustness of these patterns to spatially inconsistent sampling effort was tested using Monte Carlo‐style simulations. Levels of local endemism and species richness over numbers of samples were compared for seamount and non‐seamount areas using linear regressions. Non‐seamount populations were randomly generated from areas and depth ranges that reflected the typical sampling profile of seamounts. Results Seamount ophiuroid assemblages did not exhibit elevated levels of species richness or narrow‐range endemism compared with non‐seamount areas. Seamounts can exhibit high overall species richness for low numbers of samples, particularly on seamounts supporting a dense coral matrix, but this does not increase with additional sampling at the rates found in non‐seamount areas. There were relatively few identifiable seamount specialists. In general, seamount faunas reflected those found at similar depths in surrounding areas, including the continental slope. Seamount and non‐seamount faunas within the study area exhibited congruent latitudinal and bathymetric species turnover. Main conclusions Seamount faunas were variable for ophiuroid faunal composition, species richness and narrow‐range endemism, reflecting their environmental diversity and complex history. The continental slope was also variable, with some areas being particularly species rich. Broad geomorphological habitat categories such as ‘seamounts’ or ‘continental slope’ may be at the wrong scale to be useful for conservation planning.     

Cold‐water coral habitats on seamounts: do they have a specialist fauna?

Aim The large biogenic structures formed by colonial cold‐water scleractinian corals provide valuable habitat for marine invertebrates on seamounts and the continental slope of all world oceans. These patchily distributed long‐lived structures are easily damaged by several human activities, particularly bottom trawling for fish, and are potentially vulnerable to ocean acidification caused by climate change. Consequently, an important conservation question is whether these structures support a specialized invertebrate fauna restricted to these habitats. Here we investigate the relationship between structures formed by the coral Solenosmilia variabilis and its associated ophiuroid (brittlestar) fauna, one of the dominant components of deep‐sea ecosystems. Location Seafloor habitat around Southern Australia, New Zealand, and the Macquarie Ridge from 35 to 53° S and 117° E–176° W, 500–1500 m depth. Methods Data were derived from samples collected by numerous scientific expeditions to the study region. Because these samples were collected using a variety of gear and effort, a two‐step approach was used. First, the largest consistently collected data set (73 ophiuroid species from 59 samples) was assembled for multivariate analysis. ANOSIM was used to test for differences in ophiuroid community composition between Solenosmilia and non‐Solenosmilia habitat on seamounts and the continental slope, and SIMPER was used to identify species that characterized Solenosmilia habitat. Second, these results were validated against all known data to ensure that these characteristic species had not been found in non‐Solenosmilia habitat elsewhere. Results The ophiuroid assemblages from Solenosmilia habitat were distinct from those found on other habitats on the continental slope and offshore seamounts across the study region. Although a suite of ophiuroid species characterized Solenosmilia habitat, most have also been collected from dead coral or other rubble, suggesting a physical rather than biological association between the coral matrix and its associated invertebrate fauna. Main conclusions Despite the lack of an exclusive ophiuroid–coral relationship, cold‐water scleractinian coral remains the principal habitat for a number of ophiuroid species across southern Australia and New Zealand. The slow growth rate of the coral and the low dispersal potential of some associated species suggest that recovery of damaged cold‐water coral assemblages will be a long‐term process.     

Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores,including one new genus and three new species

The Hippasterinae is a subfamily within the Goniasteridae, consisting of five genera and 26 species, which occur in cold‐water settings ranging from subtidal to abyssal depths. All known genera were included in a cladistic analysis resulting in two most parsimonious trees, supporting the Hippasterinae as monophyletic. Our review supports Sthenaster emmae gen. et sp. nov. as a new genus and species from the tropical Atlantic and two new Evoplosoma species, Evoplosoma claguei sp. nov. and Evoplosoma voratus sp. nov. from seamounts in the North Pacific. Hippasteria caribaea is reassigned to the genus Gilbertaster, which previously contained a single Pacific species. Our analysis supports Evoplosoma as a derived deep water lineage relative to its continental‐shelf, shallow water sister taxa. The genus Hippasteria contains approximately 15 widely distributed, but similar‐looking species, which occur in the northern and southern hemispheres. Except for Gilbertaster, at least one species in each genus has been observed or is inferred to prey on deep‐sea corals, suggesting that this lineage is important to the conservation of deep‐sea coral habitats. The Hippasterinae shares several morphological similarities with Circeaster and Calliaster, suggesting that they may be related. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 266–301.     

The potential impact of a krill fishery upon pelagic fish in the Prydz Bay area of Antarctica

Summary RMT hauls taken during FIBEX in the Prydz Bay region showed a relatively high incidence of fish compared with most previous reports from the Atlantic sector. Overall, fish comprised 3.8% by number and 8.1% by weight, and these figures rose to 26.8 and 46.1%, respectively in aimed hauls over the continental shelf. Even when only hauls with>50% E. superba are considered, fish accounted for almost 1% by weight of the catch overall, and more in aimed hauls or those taken over the continental shelf. Species composition differed markedly between the continental shelf and deep water zones. Over the shelf the fish catch comprised mainly Pleuragramma antarcticum and channichthyid juveniles, while over deep water it consisted mainly of myctophids and Notolepis coatsi. These data indicate that the potentially large krill fishery in this region could affect the populations of some shelf dwelling demersal species by increasing the mortality among their pelagic juvenile stages.     

Six microsatellite loci from the deep‐sea coral Corallium lauuense (Octocorallia: Coralliidae) from the islands and seamounts of the Hawaiian archipelago

Gorgonian octocorals are among the dominant deep‐sea benthic taxa of many seamounts. Seamount fauna are threatened by destructive fisheries practices, yet little is known about the physical and biological processes that maintain species on seamounts. Few informative molecular markers have been found in deep‐water corals or in gorgonian octocorals. Here we report the characterization of six highly polymorphic microsatellite loci for the deep‐sea precious coral Corallium lauuense from Hawaii using enriched genomic DNA libraries. These loci are being used to examine gene flow and stock structure among seamount and island populations to better understand dispersal and connectivity of seamount species.     

Fish Biodiversity of the Vitória-Trindade Seamount Chain,Southwestern Atlantic: An Updated Database

Despite a strong increase in research on seamounts and oceanic islands ecology and biogeography, many basic aspects of their biodiversity are still unknown. In the southwestern Atlantic, the Vitória-Trindade Seamount Chain (VTC) extends ca. 1,200 km offshore the Brazilian continental shelf, from the Vitória seamount to the oceanic islands of Trindade and Martin Vaz. For a long time, most of the biological information available regarded its islands. Our study presents and analyzes an extensive database on the VTC fish biodiversity, built on data compiled from literature and recent scientific expeditions that assessed both shallow to mesophotic environments. A total of 273 species were recorded, 211 of which occur on seamounts and 173 at the islands. New records for seamounts or islands include 191 reef fish species and 64 depth range extensions. The structure of fish assemblages was similar between islands and seamounts, not differing in species geographic distribution, trophic composition, or spawning strategies. Main differences were related to endemism, higher at the islands, and to the number of endangered species, higher at the seamounts. Since unregulated fishing activities are common in the region, and mining activities are expected to drastically increase in the near future (carbonates on seamount summits and metals on slopes), this unique biodiversity needs urgent attention and management.     

Spatial and temporal patterns of genetic variation in the widespread antitropical deep‐sea coral Paragorgia arborea

Numerous deep‐sea species have apparent widespread and discontinuous distributions. Many of these are important foundation species, structuring hard‐bottom benthic ecosystems. Theoretically, differences in the genetic composition of their populations vary geographically and with depth. Previous studies have examined the genetic diversity of some of these taxa in a regional context, suggesting that genetic differentiation does not occur at scales of discrete features such as seamounts or canyons, but at larger scales (e.g. ocean basins). However, to date, few studies have evaluated such diversity throughout the known distribution of a putative deep‐sea species. We utilized sequences from seven mitochondrial gene regions and nuclear genetic variants of the deep‐sea coral Paragorgia arborea in a phylogeographic context to examine the global patterns of genetic variation and their possible correlation with the spatial variables of geographic position and depth. We also examined the compatibility of this morphospecies with the genealogical‐phylospecies concept by examining specimens collected worldwide. We show that the morphospecies P. arborea can be defined as a genealogical‐phylospecies, in contrast to the hypothesis that P. arborea represents a cryptic species complex. Genetic variation is correlated with geographic location at the basin‐scale level, but not with depth. Additionally, we present a phylogeographic hypothesis in which P. arborea originates from the North Pacific, followed by colonization of the Southern Hemisphere prior to migration to the North Atlantic. This hypothesis is consistent with the latest ocean circulation model for the Miocene.     

Clones or clans: the genetic structure of a deep‐sea sponge,Aphrocallistes vastus,in unique sponge reefs of British Columbia,Canada

Understanding patterns of reproduction, dispersal and recruitment in deep‐sea communities is increasingly important with the need to manage resource extraction and conserve species diversity. Glass sponges are usually found in deep water (>1000 m) worldwide but form kilometre‐long reefs on the continental shelf of British Columbia and Alaska that are under threat from trawling and resource exploration. Due to their deep‐water habitat, larvae have not yet been found and the level of genetic connectivity between reefs and nonreef communities is unknown. The genetic structure of Aphrocallistes vastus, the primary reef‐building species in the Strait of Georgia (SoG) British Columbia, was studied using single nucleotide polymorphisms (SNPs). Pairwise comparisons of multilocus genotypes were used to assess whether sexual reproduction is common. Structure was examined 1) between individuals in reefs, 2) between reefs and 3) between sites in and outside the SoG. Sixty‐seven SNPs were genotyped in 91 samples from areas in and around the SoG, including four sponge reefs and nearby nonreef sites. The results show that sponge reefs are formed through sexual reproduction. Within a reef and across the SoG basin, the genetic distance between individuals does not vary with geographic distance (r = ?0.005 to 0.014), but populations within the SoG basin are genetically distinct from populations in Barkley Sound, on the west coast of Vancouver Island. Population structure was seen across all sample sites (global F_ST = 0.248), especially between SoG and non‐SoG locations (average pairwise F_ST = 0.251). Our results suggest that genetic mixing occurs across sponge reefs via larvae that disperse widely.     

Local endemism and within‐island diversification of shrews illustrate the importance of speciation in building Sundaland mammal diversity

Island systems are important models for evolutionary biology because they provide convenient, discrete biogeographic units of study. Continental islands with a history of intermittent dry land connections confound the discrete definitions of islands and have led zoologists to predict (i) little differentiation of terrestrial organisms among continental shelf islands and (ii) extinction, rather than speciation, to be the main cause of differences in community composition among islands. However, few continental island systems have been subjected to well‐sampled phylogeographic studies, leaving these biogeographic assumptions of connectivity largely untested. We analysed nine unlinked loci from shrews of the genus Crocidura from seven mountains and two lowland localities on the Sundaic continental shelf islands of Sumatra and Java. Coalescent species delimitation strongly supported all currently recognized Crocidura species from Sumatra (six species) and Java (five species), as well as one undescribed species endemic to each island. We find that nearly all species of Crocidura in the region are endemic to a single island and several of these have their closest relative(s) on the same island. Intra‐island genetic divergence among allopatric, conspecific populations is often substantial, perhaps indicating species‐level diversity remains underestimated. One recent (Pleistocene) speciation event generated two morphologically distinct, syntopic species on Java, further highlighting the prevalence of within‐island diversification. Our results suggest that both between‐ and within‐island speciation processes generated local endemism in Sundaland, supplementing the traditional view that the region's fauna is relictual and primarily governed by extinction.     

Patterns of distribution for southern Australian marine echinoderms and decapods

Aim To relate patterns of distribution of marine echinoderms and decapods around southern Australia to major ecological and historical factors. Location Shallow‐water (0–100 m) marine waters off southern Australia, south of 30° S. Methods (1) Record the presence/absence of known echinoderm and decapod species in cells of c. 1° latitude and longitude, along the coast of southern mainland Australia and Tasmania. (2) Describe patterns in species composition, species richness and endemism through gradient analysis, ordination and cluster analysis. (3) Relate these patterns to distance and temperature gradients, the area of continental shelf, the average size of species range, and known historical factors. Results Species composition varied with both latitude and longitude. Species richness was relatively constant from east to west but graded with latitude from high in the warm‐temperate regions around Perth and Sydney to low in cool‐temperate southern Tasmania. Species richness was not related to the area of continental shelf or average species range size. Species turnover was not correlated with rates of temperature change. It was problematic to separate distance from temperature gradients, but there was evidence that the southern distribution limits of some species are related to minimum sea surface temperature. Within the taxonomic groups surveyed, evolutionary radiation has been largely limited to a few cosmopolitan species‐rich genera. Main conclusions There are historical as well as ecological hypotheses explaining the latitudinal gradient of marine species richness in southern Australia: (1) the continual invasion and speciation of species of tropical origin as Australia has split from Gondwana and drifted northward; (2) progressive extinction of some Gondwanan cool‐temperate species at the limits of their range; (3) low level of immigration of additional cool‐temperate species; and (4) some in situ endemic speciation.     

Skate assemblage on the eastern Patagonian Shelf and Slope: structure, diversity and abundance

The eastern Patagonian Shelf and continental slope of the south-west Atlantic Ocean support a high biodiversity and abundance of skates. In this study, meso-scale differences in the assemblages, spatial and seasonal distributions of skates are revealed among six habitat zones of the eastern Patagonian Shelf characterized by distinctive oceanographic conditions. Most skates belonged to temperate fauna, and their abundance was much greater in habitats occupied by temperate waters (north-western outer shelf) or mixed waters (northern slope) than in habitats occupied by sub-Antarctic waters (SASW) (south-eastern outer shelf and southern slope). Sub-Antarctic skates were not abundant on the shelf even in habitats occupied by SASW, occurring mainly in deep areas of the lower continental slope. The majority of temperate skates migrated seasonally, shifting northward in winter and spreading southward with warming waters in summer. Most temperate species had two peaks in female maturity (mainly spring and autumn) and spawned in the same habitats where they fed. It is hypothesized that the high biodiversity and abundance of skates on the Patagonian Shelf and Slope are due to the practical absence of their natural competitors, flatfishes, which occupy similar eco-niches elsewhere.     

Demersal fish assemblages on seamounts exploited by fishing in the Azores (NE Atlantic)

Seamount fish communities are susceptible to variations due to the oceanographic conditions and level of historical fishing effort. In the NE Atlantic, the Azores is considered an “oceanic seamount ecosystem area” because seamount concentration is high relative to other regions. Scientific information on seamounts in the Azores remains scarce and demersal fishery occurs mostly without any knowledge to endorse sustainable harvest strategies. To make available an important baseline information on dynamics of demersal fish populations inhabiting commercially exploited seamounts, the present study has as specific objectives to (a) describe the taxonomic composition of demersal fish assemblages on underwater mountains, (b) examine whether assemblages vary spatial and temporally, and (c) investigate what drives distributional patterns of species in terms of abundance and size composition. For this, three Azorean seamounts (Açores, Princesa Alice and Mar da Prata) exploited by bottom fishing were selected as case study areas. Data were obtained from scientific surveys and commercial fishery over the past c. 25 years. A total of 84 species from 45 families were identified. Sebastidae, Moridae, Sparidae and Centrophoridae were the most abundant families, mainly represented by Helicolenus dactylopterus, Mora moro, Pagellus bogaraveo and Deania profundorum, respectively. Fish assemblages were more distinguishable spatially than temporally. Depth was identified as the main factor responsible for these differences. The higher occurrence of shallow and intermediate (i.e., up to 600 m) habitats in Princesa Alice and Açores seems to favor the occurrence of a greater number of species and higher abundances in comparison to Mar da Prata. Phycis phycis, Pontinus kuhlii, H. dactylopterus, P. bogaraveo, Conger conger and M. moro were the species which primarily contributed to dissimilarities in assemblage structure among sample groups. Abundance indices and fish sizes showed a decreasing trend for many of these species, especially for those with sedentary behaviour inhabiting historically highly exploited seamount areas. These results highlighted the vulnerability of demersal fishes to the expansion of fishing effort in the offshore seamount areas. Spatial management of seamounts should be a priority being fish conservation balanced with strategies that support sustainable fisheries.     

Investigating the environmental drivers of deep‐seafloor biodiversity: A case study of peracarid crustacean assemblages in the Northwest Atlantic Ocean

The deep‐sea benthos covers over 90% of seafloor area and hosts a great diversity of species which contribute toward essential ecosystem services. Evidence suggests that deep‐seafloor assemblages are structured predominantly by their physical environment, yet knowledge of assemblage/environment relationships is limited. Here, we utilized a very large dataset of Northwest Atlantic Ocean continental slope peracarid crustacean assemblages as a case study to investigate the environmental drivers of deep‐seafloor macrofaunal biodiversity. We investigated biodiversity from a phylogenetic, functional, and taxonomic perspective, and found that a wide variety of environmental drivers, including food availability, physical disturbance (bottom trawling), current speed, sediment characteristics, topographic heterogeneity, and temperature (in order of relative importance), significantly influenced peracarid biodiversity. We also found deep‐water peracarid assemblages to vary seasonally and interannually. Contrary to prevailing theory on the drivers of deep‐seafloor diversity, we found high topographic heterogeneity (at the hundreds to thousands of meter scale) to negatively influence assemblage diversity, while broadscale sediment characteristics (i.e., percent sand content) were found to influence assemblages more than sediment particle‐size diversity. However, our results support other paradigms of deep‐seafloor biodiversity, including that assemblages may vary inter‐ and intra‐annually, and how assemblages respond to changes in current speed. We found that bottom trawling negatively affects the evenness and diversity of deep‐sea soft‐sediment peracarid assemblages, but that predicted changes in ocean temperature as a result of climate change may not strongly influence continental slope biodiversity over human timescales, although it may alter deep‐sea community biomass. Finally, we emphasize the value of analyzing multiple metrics of biodiversity and call for researchers to consider an expanded definition of biodiversity in future investigations of deep‐ocean life.     

Influence of estuarine and continental shelf water advection on the coastal movements of apron ray Discopyge tschudii in the Southwestern Atlantic

Evaluated was the seasonal and inter‐annual association between habitat variables and distribution pattern of the apron ray (Discopyge tschudii) and its relationship, with the main force on the environmental condition to understand the influence of estuarine and continental shelf processes in the coastal fishes of the Southwestern Atlantic Coastal System (34°–41°S). Two winter and five spring research surveys in the SACS were analyzed and the Perry and Smith methodology applied to determine the seasonal association of depth, temperature and salinity and the abundance of apron ray. The season with the highest inter‐annual spatial distribution variation was related to the main external force on environmental conditions (e.g. wind, atmospheric temperature, and Río de la Plata discharge and shelf water intrusion). Apron ray showed persistent habitat selection, with the water temperature (<16°C) and salinity (higher than 31.8) being environmental factors most influencing its spatial distribution. In the spring, the apron ray spatial distribution showed higher inter‐annual variation than in winter. The persistence of the spring habitat selection of D. tschudii suggests that its onshore‐offshore as well as north‐south movements are influenced by water mass movements forced by a combination of local conditions (wind) and regional‐scale weather patterns (e.g. strength of the Malvinas Current). This study provides evidence on the importance of considering environmental conditions on the spatial distribution of apron ray and improves the knowledge on interactions between estuarine and shelf water dynamics as determinants of the spatial distribution of a coastal fish species in the Southwest Atlantic Coastal System.     

Dynamics of black spot sea bream (Pagellus bogaraveo) mean length: evaluating the influence of life history parameters, recruitment, size selectivity and exploitation rates

Stochastic simulations were used to evaluate the influence of recruitment pattern (log‐normal, decreasing), size selectivity (normal, logistic model) and fishing mortality pattern (abrupt, continuous increase in fishing mortality) on the evolution of mean length and the dispersion of mean length for a relatively long‐lived deep‐water species, the black spot sea bream (Pagellus bogaraveo). An abrupt increase in fishing mortality resulted in mean size decreasing and stabilizing at a lower level while a steady increase in fishing mortality caused the continuous decrease in mean size that has been reported for many long‐lived species. Decrease in mean size was greatest for logistic model simulations and for cases where fish were susceptible to capture at a small size. Logistic selectivity, with decreasing recruitment and increasing fishing mortality over time, resulted in mean length and variability in mean length trends similar to that observed for the Strait of Gibraltar fishery. Furthermore, it was found with the declining recruitment that moderate increases in fishing mortality can result in significant decreases in mean length. Given the importance of mean size as an indicator of the state of a resource, these simulations are a useful alternative or complement to standard fisheries assessment methods, helping to provide information on exploitation patterns and rates that can be used for conservation and management.     

Assemblages of sea stars (Echinodermata: Asteroidea) and brittle stars (Echinodermata: Ophiuroidea) in the Weddell Sea (Antarctica) and off Northeast Greenland (Arctic): a comparison of diversity and abundance

Composition and distribution of asteroid and ophiuroid assemblages were investigated by means of Agassiz trawl catches at 34 stations in 220- to 1,200-m depth in the Weddell Sea and at 17 stations in 90- and 830-m depth off Northeast Greenland. A total of 86 species (48 sea stars, 38 brittle stars) were identified in the Weddell Sea whereas off Northeast Greenland a total of 26 species (16 sea stars, 10 brittle stars) were recorded. In both study areas, brittle stars were numerically more important than sea stars, and abundances generally decreased with water depths. Multivariate analyses revealed a conspicuous depth zonation of sea and brittle stars off Greenland. Very high abundances of Ophiocten sericeum and Ophiura robusta characterized the assemblages on shallow shelf banks whereas in greater depths Ophiopleura borealis, Ophioscolex glacialis and Ophiacantha bidentata became dominant, albeit at significantly lower densities. Mass occurrences of brittle stars, such as those recorded on Greenlandic shelf banks, have not been discovered in the Weddell Sea, where distinct assemblages were discriminated in deep shelf trenches as well as on the eastern and southern shelf. Ophioplocus incipiens, Ophiurolepis martensi and Ophiurolepis brevirima were the most prominent species on the eastern shelf. Ophiacantha antarctica, Ophiurolepis gelida and Ophionotus victoriae on the southern shelf, and Ophiosparte gigas as well as the asteriod Hymenaster sp., in the shelf trenches. Overall, the Weddell Sea housed conspicuously more asterozoan species than the waters off Greenland. Higher species diversity was also evident at both a regional and local scale, especially for the eastern Weddell Sea shelf. However, because many species from the Weddell Sea are closely related, the Weddell Sea assemblages were not significantly different from the Greenland ones in terms of taxonomic diversity and distinctness. Received: 29 April 1996/Accepted: 10 June 1996     

Home on the range: spatial ecology of loggerhead turtles in Atlantic waters of the USA

Aim Although satellite tracking has yielded much information regarding the migrations and habitat use of threatened marine species, relatively little has been published about the environmental niche for loggerhead sea turtles Caretta caretta in north‐west Atlantic waters. Location North Carolina, South Carolina and Georgia, USA. Methods We tracked 68 adult female turtles between 1998 and 2008, one of the largest sample sizes to date, for 372.2 ± 210.4 days (mean ± SD). Results We identified two strategies: (1) ‘seasonal’ migrations between summer and winter coastal areas (n = 47), although some turtles made oceanic excursions (n = 4) and (2) occupation of more southerly ‘year‐round’ ranges (n = 18). Seasonal turtles occupied summer home ranges of 645.1 km² (median, n = 42; using α‐hulls) predominantly north of 35 ° latitude and winter home ranges of 339.0 km² (n = 24) in a relatively small area on the narrow shelf off North Carolina. We tracked some of these turtles through successive summer (n = 8) and winter (n = 3) seasons, showing inter‐annual home range repeatability to within 14.5 km of summer areas and 10.3 km of winter areas. For year‐round turtles, home ranges were 1889.9 km². Turtles should be tracked for at least 80 days to reliably estimate the home range size in seasonal habitats. The equivalent minimum duration for ‘year‐round’ turtles is more complex to derive. We define an environmental envelope of the distribution of North American loggerhead turtles: warm waters (between 18.2 and 29.2 °C) on the coastal shelf (in depths of 3.0–89.0 m). Main conclusions Our findings show that adult female loggerhead turtles show predictable, repeatable home range behaviour and do not generally leave waters of the USA, nor the continental shelf (< 200m depth). These data offer insights for future marine management, particularly if they were combined with those from the other management units in the USA.     

Application of otolith mass and shape for discriminating scabbardfishes Aphanopus spp. in the north‐eastern Atlantic Ocean

The otolith was used to investigate the variability between Aphanopus carbo and Aphanopus intermedius inhabiting the north‐eastern Atlantic Ocean. The results indicate a high degree of morphological affinity between species and areas; a noticeable metabolic change in the otolith shape was noted in the specimens of A. carbo, which may be related to migrations of individuals from shallow water (closer to the continental coast) to deeper water (archipelagos of Madeira and the Canary Islands). The results suggest a single population for both species in the north‐eastern Atlantic Ocean, although not conclusively.