The slipper limpet Crepidula fornicata ranks among the main invasive species on French coasts and is known to cause ecological impacts on food web structure and nutrient cycling. This study investigated the effect of C. fornicata on different components of benthic megafauna diversity (species composition, α-, β- and γ-diversity). In Arcachon Bay (France), C. fornicata was present in 58% of the 221 sampling stations. Crepidula fornicata was particularly abundant in four of the main benthic megafauna assemblages, suggesting a non-random distribution of its population. The mean number of megafauna species per station (α-diversity) was 11 with C. fornicata vs six without. Conversely, community similarity among stations (β-diversity) was higher when C. fornicata biomass increased. Opposing α- and β-diversity trends in the presence of C. fornicata explained the similarity of the global number of species (γ-diversity) between both situations (with and without C. fornicata). These results highlighted how this exotic engineer species acted on different types of diversity: the presence of C. fornicata increased the number of species per sample (α-diversity) but homogenized the benthic community (decreasing β-diversity) in comparison with stations where C. fornicata was absent. Crepidula fornicata stock in Arcachon Bay was also monitored and compared with 1999. The spread of C. fornicata between 1999 and 2011 has been limited with a 318 t stock which was not statistically different than the previous estimate performed in 1999. However, the mean length of C. fornicata collected in 2011 was significantly smaller, mainly due to a higher proportion of small individuals.

Benthic habitat composition is a key factor that structures assemblages of coral reef fishes. However, natural and anthropogenic induced disturbances impact this relationship. This study investigates the link between benthic habitat composition and fish functional groups in four countries in the Western Indian Ocean (WIO). Benthic composition of 32 sites was quantified visually from percentage cover of hard and soft corals, rubble, turf, fleshy and crustose coralline algae. At each site, abundance of 12 coral-associated fish functional groups in 50 × 5 m transects was determined. Cluster analysis characterized reefs based on benthic cover and revealed five habitat types (A, B, C, D and E) typified by decreasing cover of hard corals, increasing cover of turf and/or fleshy algae and differences in benthic diversity. Habitat type A was present in all four countries. Other habitats types showed geographic affiliations: notably Comoros sites clustered in either habitats B or E, northern Madagascar had B, C and D type habitats, whereas sites in central Tanzania and northern Mozambique had habitats D and E. Fish functional groups showed significant linkages with some habitat types. The abundances of corallivores, invertivores, detritivores and grazers were higher in habitat B, whereas planktivores and small excavators showed lower abundances in the same habitat. These linkages between benthic habitat types and fish functional groups are important in informing priority reefs that require conservation and management planning.

Historical strandings and sightings (1989–2016) of Tursiops truncatus at 25oS in the south-western Atlantic Ocean (Paraná, Brazil) were assessed to (1) investigate temporal fluctuations; and (2) quantify biological, ecological and health parameters of regional populations. In total, 57 T. truncatus carcasses in mostly advanced stages of decomposition (~80% of all specimens) were recorded. Standardized temporal strandings (per observational effort) varied considerably and with no clear annual relationship beyond a peak in 2007, but there were consistently more strandings in winter/spring (74%) than summer/autumn (26%). While there was uncertainty over age estimation (i.e. not available for the population), individuals classified as juveniles/subadults were more frequent (80%) than calves (14%) and adults (6%). Of 28 carcasses assessed, 27 showed a positive linear relationship between TL and condyle-basal length, while one specimen had a clear southern skull morphotype. Suggestive lesions of Crassicauda sp. were recorded in 77% of assessed skulls and four types of tooth pathologies were observed. Nine individuals were more closely investigated for gross and histopathological alterations and had clear evidence of fishery interactions and various health issues associated with disease and oedema accompanied by alveolar fibrosis. While the regional frequency of T. truncatus strandings was lower than other more vulnerable cetaceans, the absolute numbers (e.g. 15 individuals in 2016) and some uncertainty concerning regional taxonomy are noteworthy, and justify ongoing spatio-temporal monitoring. Further, given the evidence of disease in some specimens, future work should not only encompass rigorous taxonomic assessments, but also health to comprehensively evaluate regional stocks. Small cetacean species are sentinels and their condition could inform ongoing environmental assessments.

Marine benthic populations are dependent on early life-history stages surviving multiple population bottlenecks. Failure at one or several of these bottlenecks can alter species’ patterns of distribution and abundance. The barnacle Semibalanus balanoides is found along temperate and sub-arctic shorelines of the Atlantic and Pacific Oceans. Over the past century the southern range limits of S. balanoides have shifted hundreds of kilometres poleward on both coasts of the Atlantic. Here we tested if temperature limits fertilization and used these data, along with those from previous studies, to create mechanistic biogeographic models to understand which potential population bottlenecks in the early life-history of S. balanoides influence its distribution and abundance. In the western Atlantic survival of new recruits is probably more important in setting the southern range limit than the effects of temperature on early life-history stages because fertilization, brooding and the probability of larval release matching phytoplankton availability were all predicted to be high near the historical range edge. Phytoplankton mismatch may partially explain the ephemeral nature of S. balanoides in some parts of the English Channel. Further south along the coast of France predicted brooding success was reduced in a pattern consistent with historical range shifts in this region. Within Galicia, Spain fertilization was predicted to be low near the southern limit, and likely plays an important role in setting this range edge. Mismatches between phytoplankton abundance and larval release in Galicia may further limit reproductive success within this region.

Chondrichthyans are usually caught incidentally in fisheries for species of high commercial value and then discarded on board or landed as by-products. On the coast of Chubut province and adjacent waters (43°00′S–44°56′S) a bottom trawl fishery has developed targeted at the Patagonian shrimp (Pleoticus muelleri) and common hake (Merluccius hubbsi). Since 2005, this fishery has been monitored by the On-board Observers Program of Chubut province (POBCh). With the aim of advancing towards an ecosystem approach, POBCh not only collects information about target species but also about all the species caught by the trawl nets of the province fisheries. From the information collected by this programme it was possible to identify and record the chondrichthyan species vulnerable to the fishing gear used by the coastal fleet that operates from Puerto Rawson. The composition of the fleet catch was characterized according to the target species during the 2005–2014 period. In the analysis of 3786 hauls, 23 species of chondrichthyans (seven species of sharks, 15 species of batoids and a single species of Holocephali) were identified. Seven species showed a frequency of occurrence greater than 10% (Callorhinchus callorynchus, Discopyge tschudii, Mustelus schmitti, Sympterygia bonapartii, Psammobatis normani, Squalus acanthias and Zearaja chilensis). Species spatial distribution was evaluated and five areas of species assemblages were established. Besides the aspects related to bycatch, these analyses have contributed to the knowledge of the chondrichthyan biodiversity in the provincial coast where the fleet operates, a region with incomplete and mostly dispersed and outdated information.

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.

The population size structure from a total of 876 individuals, together with published values of growth rate, maximum size and size at age were used to estimate an instantaneous rate of natural mortality (M) of 0.46–0.59 year−1 in a population of the sea star Archaster angulatus from south-western Australia. Peak abundance (17%) of all animals sampled was 105–109 mm arm radius (means of 4.2–4.8 years of age) and only one per cent of sea stars are predicted to live beyond 8 years in the population studied. There are few comparable studies on sea stars but when compared with rates of natural mortality in other echinoderms (sea urchins), A. angulatus is intermediate among species which exhibit the extremes of life history strategies, that is, those which grow very rapidly and may live just two years or less and those with very slow growth rates and which may live for decades.

Two new species of free-living marine nematodes, Litinium dispariseta sp. nov. and Wieseria minor sp. nov. are described from an abyssal plain with a water depth of 4117–5035 m near the Southern Kyushu-Palau Ridge in the tropical Western Pacific Ocean. Litinium dispariseta sp. nov. is characterized by having distinct inner labial setae two times longer than the outer labial setae, wrench-like amphideal foveas, a single preanal midventral supplementary seta and a short cylindrical tail with bluntly rounded tip. It differs from congeners by its distinctly long inner labial setae relative to the outer labial setae (two times longer vs shorter or equal in length) and peculiar wrench-like amphideal foveas (vs horseshoe shaped or ovoid with round to oval anterior aperture). Wieseria minor sp. nov. has a clavate tail, a character found only in the four congeners W. glandulosa (Kreis, 1929), W. longiseta (Allgén, 1947), W. clavata Gerlach, 1956 and W. inaequalis Gerlach, 1956. However, Wieseria minor sp. nov. differs from these congeners by its much smaller body size (1045 µm vs 2120–3125 µm) and oblong amphideal foveas with double contour (vs a single oblong or ovoid loop). An emended diagnosis for Wieseria and pictorial keys for Litinium and Wieseria are provided.

Population outbreaks of the coral-eating predator crown of thorns starfish (COTS), Acanthaster planci are responsible for large-scale disturbance of coral reefs throughout the Indo-Pacific. In response, attempts are often made to control COTS outbreaks in protected areas. For instance, volunteers remove thousands of sea stars every year in Malaysia. This study reports the status of the COTS population in the Pulau Tioman Marine Park and examines the effectiveness of the seasonal sea star removal programme. After the 2009 removal season, we monitored COTS densities and coral assemblages before and after a 6-month no-removal season at sites with and without COTS removal efforts. We recorded high COTS densities up to 330 ind. ha−1 at a few sites independent of removal effort. In fact, removal only temporarily reduced large individuals from local populations. Moreover, after the no-removal season, sites with COTS removal had increased live coral cover, but sites without COTS removal had a drastic decrease in live coral cover, with Acropora spp. being most affected. Therefore, this study suggests that the current seasonal removals could promote coral health, despite the high density of COTS.

In order to investigate social structure, 11 years of individual photo-identification data of bottlenose dolphin were analysed. We examined the type of association indices between pairs of identified individuals; the patterns of affiliation between individual dolphins and the probabilities of association between individuals over time. Between 2001 and 2012, there were 272 encounters which resulted in the identification of 501 individuals. The discovery curve resulting from the photo-identification analysis indicated an open population with regular recruitment of new individuals. All individuals were found to be associated at an association index of <0.05. A total of 291 individuals recorded from 2004 to 2012 were used to assess the temporal pattern of the social structure. The model fit to the Standardized Lagged Association Rate (SLAR) that best described the studied bottlenose dolphin population was ‘casual acquaintances’, and the analysis of associations over time showed a decreasing SLAR curve that falls until reaching the null rate, confirming random associations. The decline of the SLAR curve after ~500 days (1.4 years) suggests disassociation over that time period which can be explained by demographic events such as mortality or emigration. In an open ocean habitat like Madeira this is not unexpected, as there are neither geographic boundaries nor enclosed environments. This population presented a dynamic and fluctuating social structure, where groups change in size and composition. In future conservation efforts this population should be considered as one large community, where individuals associate, disassociate and reassociate with each other over time.

Coastal ecosystems are particularly vulnerable to alien invasions. Regular, standardized, targeted monitoring of coastal areas helps to detect the arrival of non-native species early, identify sites most vulnerable to invasion, and assess potential for further spread. This study quantified the spread and changes in distribution of non-native oyster, Crassostrea gigas, populations around the coast of Ireland. In total 37 sites were surveyed, in areas which either currently or previously harboured cultivated C. gigas, for the presence and abundance of ‘wild’ C. gigas. Wild populations were identified at 20 sites and at four additional sites C. gigas was observed as recently discarded from aquaculture activity. Five of the invaded sites were identified as being highly suitable for a population expansion based on their current population status. Importantly, we also identified individuals of C. gigas and native European oysters, Ostrea edulis, co-occurring within the same shore at five sites. This is the first record to our knowledge of such co-occurrence within Europe. This evidence of co-existing oyster species raises concerns regarding the potential impact of C. gigas on recovering O. edulis populations. In Ireland, however, C. gigas does not typically spread extensively from introduction points, and although self-containing populations exist, they are currently sustained at a much lower density than those observed in other regions such as the Wadden Sea or French Atlantic coasts. We suggest, therefore, that to protect native oyster populations, C. gigas should be eradicated where co-occurring with O. edulis and recommend continuous monitoring of invaded sites.

The Atlantic–Mediterranean transition zone between the Alborán Sea and the Gulf of Cádiz constitutes the most prominent marine geographic barrier in European waters and includes known phylogeographic breaks such as the Strait of Gibraltar and the Almería-Oran Front. A genetic shift in this area has been previously documented for the European littoral shrimp Palaemon elegans. Here we carried out a phylogeographic analysis with the congeneric and sympatric species Palaemon serratus to test for similar intraspecific genetic differentiation and geographic structure. This littoral prawn is distributed in the Northeastern Atlantic Ocean, the Mediterranean Sea and the Black Sea. We compared DNA sequences from the mitochondrial genes Cox1 and to a lesser extent from 16S rRNA of several Atlantic and Mediterranean populations. Furthermore, sequences from the nuclear gene Enolase were included for corroborating differences between Mediterranean and Atlantic individuals. A pronounced genetic differentiation was detected between the Mediterranean and Atlantic populations, amounting to 10.14% in Cox1 and 2.0% in 16S, indicating the occurrence of two independent evolutionary lineages. Interestingly, specimens from the Atlantic Gulf of Cadiz cluster together with the Mediterranean individuals, indicating that a biogeographic barrier appears to be located west of the Strait of Gibraltar.

Weight–Body Length relationships (WLR) of 45 fish species (37 Actinopterygii and eight Elasmobranchii) were investigated. A total of 31,167 individuals were caught and their biological parameters measured during the four quarters from 2013 to 2015, on five scientific surveys sampling the North-eastern Atlantic Ocean from the North Sea to the Bay of Biscay (ICES Divisions IVb, IVc, VIId, VIIe, VIIg, VIIh, VIIj, VIIIa and VIIIb). Among 45 tested species, all showed a significant correlation between total length (L) and total weight (W). The influence of sex on WLR was estimated for 39 species and presented a significant sexual dimorphism for 18 species. Condition factor (K) of females was always higher than for males. Moreover, a spatial effect on the WLR according to five ecoregions (the Bay of Biscay, the Celtic Sea, the Western English Channel, the Eastern English Channel and the North Sea), was significant for 18 species among 38 tested species. The temporal effect was tested according to components (year and quarter/season). The seasonality effect on WLR is more frequently significant than the year especially for the Elasmobranchii species, and can be related to the spawning season. Finally, depressiform species (skates, sharks and flatfish) are characterized by positive allometric growth, whereas there is no such clear pattern regarding roundfishes growth, whatever their body shape is.

A new species of holothurian of the genus Psolus Oken, 1815 is described. Psolus rufus sp. nov. was found in the central Cantabrian slope (Bay of Biscay) at 1500 m depth. The new species is characterized by having: ovoid body, reddish colour in vivo; dorsal area enclosed in a complete test composed of imbricating scales; 10 triangular plates of the same size surrounding mouth; 10 oral tentacles; no dorsal papillae; tube feet in two rows in the ventrolateral radii but one single row in the medial third or the body; ossicles are big dorsal plates and small plates in the sole, which are smooth, irregular and perforated. The molecular study of the COI gene supports the morphological results, grouping P. rufus sp. nov. together with other members of the genus. However, the new species is genetically distinct from the two groups (Antarctic and Canadian) of the available sequenced Psolus species. Furthermore, a key to the Psolus species of the north-eastern Atlantic Ocean is provided.

The present paper investigates standing stock variations of Halimeda opuntia on a sandstone reef of the South-west Atlantic Ocean, in order to better understand the role of this seaweed as a CaCO3 producer. The study was conducted over two 3-month periods, using photo quadrats to analyse the coverage area, and destructive sampling to quantify area-specific biomass and CaCO3 percentage. The alga occupied 2.4% of the substrate (4464 m2), growing as clumps with an average biomass of 1.59 kg m−2, resulting in a standing stock of 7097.8 kg of alga. This standing stock varied with environmental conditions, particularly wind speed. Assuming an exponential model for these variations, H. opuntia produced at least 13,050.14 kg (54.37 g m−2 day−1) of carbonate sediments. There was a positive correlation between changes in standing stock and coverage, but not with area-specific biomass. This suggests that net algal growth results in the occupation of new spaces, with minimal increases in height or segment density. Therefore monitoring coverage should complement traditional individual-based methods for estimating Halimeda growth and production. Combined, these approaches should result in more accurate models of the role of this alga on marine carbonate budgets.

The increasing human impact at shallow depths may be affecting the Mediterranean endemic coral Astroides calycularis irreversibly. Therefore, management tools need to be developed for use in its conservation. The main aim of this study was to test a reliable attachment methodology for restoring sites where the species has been affected by human activities. We chose an attachment technique using a marine quick-action epoxy resin, completing three treatments (control, transplanted and translocated colonies) in two sites with different hydrodynamic conditions. Control colonies were undisturbed colonies that were not manipulated; translocation colonies were dislodged and reattached in the same place; and transplantation colonies were dislodged and attached in a different area. Translocated colonies showed a higher survival than transplanted ones, and survival was also higher in environments with more hydrodynamism. Regarding growth, Analysis of Variance (ANOVA) did not show significant differences among treatments, but significant differences between areas with different hydrodynamic conditions were noted. This study confirms that it is possible to transplant or translocate colonies of this coral with the technique proposed here, which could be used in future management plans for areas impacted by humans.

This study presents for the first time the factors governing the recruitment in a rocky intertidal community of the Beagle Channel, Tierra del Fuego (54°51′S 68°29′W), Argentina. The aim of this study was to examine the effect of grazers and predators, free substrate availability and crustose coralline algae on the recruitment of the main sessile components of the intertidal: Notochthamalus scabrosus, Notobalanus flosculus, Mytilus chilensis, Perumytilus purpuratus and Aulacomya atra at three intertidal levels. For barnacles, the probability of recruitment was higher with grazers, while the contrary was observed for bivalves. The number of N. flosculus recruits was higher with increased substrate availability, while N. scabrosus recruited more with reduced free substrate in the first sampling. Mussel recruitment was higher with reduced free substrate. The highest probability of recruitment of N. scabrosus was observed at the upper level. Notably, this probability and the recruits per plot were higher at the mid level under uncaged-ORP treatment than expected for the mid level. The probability of bivalve and N. flosculus recruitment was higher at upper and lower levels, respectively. At the lower level, barnacle recruitment was higher on bare rock than on crustose coralline algae. Our results suggest that grazers increase the probability of barnacle recruitment, while the presence of sessile organisms enhances the density of mussel recruits. Almost no recruitment of bivalves was observed in ORPs over one year, showing that the secondary succession is slow in this environment.

The sea cucumber Apostichopus japonicus is a deposit-feeder and vital for marine benthic ecosystems. Hypoxia can influence the behaviour and even lead to massive mortality in A. japonicus in the wild. It is important to understand the molecular responses of A. japonicus when exposed to acute changes in dissolved oxygen (DO) concentration. In this study, RNA-seq provided a general overview of the gene expression profiles of the respiratory tree of A. japonicus exposed to DO of 8 mg l−1 (DO8), 4 mg l−1 (DO4) and 2 mg l−1 (DO2) conditions. Differentially expressed genes (DEGs) screening with the NOISeq method identified 51, 59 and 61 DEGs according to the criteria of fold change ≥2 and divergence probability ≥0.8 in the comparisons of DO2 vs DO4, DO2 vs DO8 and DO4 vs DO8, respectively. Gene ontology analysis showed that ‘cellular process’ and ‘binding’ had the most enriched DEGs in the categories of ‘biological process’ and ‘molecular function’, respectively (catalytic activity also had the most enriched DEGs in the category of ‘molecular function’ based on the comparison of DO2 vs DO8), while ‘cell’ and ‘cell part’ had the most enriched DEGs in the category of ‘cellular component’. The DEGs were mapped to 79, 81 and 104 pathways in the KEGG database, and 8, 29 and 16 pathways were significantly enriched, respectively. The DO-specific DEGs identified in this study of the respiratory tree are important targets for further research into the biochemical mechanisms involved in the response of the sea cucumber to changes in the DO concentration.

Activities displayed by animals are usually cyclic, and fluctuations in behavioural repertoires can be observed on a daily or seasonal timescale. The present study describes daily and seasonal variations in the aerial events – such as leaps, spins and slaps with body parts – by spinner dolphins in Baía dos Golfinhos, Fernando de Noronha Marine National Park, in Brazil. To measure aerial events by dolphins, we compiled and analysed data collected from January 2006 to December 2010. A total of 113,027 aerial events were recorded during 1431 days of land-based daytime observations. Our results show that the frequency of aerial events was positively correlated with the number of dolphins in the bay. The relative frequency of aerial events was higher in the rainy season, when compared with the dry season. Aerial activities also varied throughout the day, with dolphins being more active in the morning, specifically from 8:00 a.m. to 8:59 a.m., regardless of the season.

Animals develop behavioural strategies throughout life to improve their survival in nature. Juvenile activity and behaviour of the commercial tropical sea cucumber Stichopus cf. horrens were examined considering factors that may influence survival at this critical developmental stage. Wild juveniles were observed in situ to describe diel activity and movement. Wild and hatchery-reared juveniles were observed in the laboratory to evaluate the influence of different light-dark cycles and microhabitats on feeding and sheltering behaviour. All juveniles (4–54 g) displayed a distinct nocturnal activity pattern both in the field and laboratory. Nocturnal activity was strongly associated with feeding and locomotion. Wild and hatchery-reared juveniles were most active at night, displayed intermediate activity during twilight, and minimal to no activity during daytime. Movement rates of wild juveniles in situ were significantly influenced by time and size to a lesser extent. Under constant light and constant dark for 48 h, juvenile feeding rhythm was endogenously controlled and strongly entrained to natural light-dark cycles. Sheltering was directly affected by light and linked to strong phototactic and thigmotactic reflexes. Juveniles preferred vegetation as shelter compared to coral, sand or open space, and showed equal preference for seagrass and macroalgae. Deviations in behaviour of hatchery-reared juveniles under laboratory conditions indicate some degree of acclimation to an artificial environment with minimal threats and a decreased sensitivity to light. The implications of nocturnal feeding, light-induced sheltering, shelter preferences and acclimation to artificial conditions are discussed in relation to juvenile survival in nature and potential restocking of the species.