The West Atlantic trumpetfish Aulostomus maculatus is a species of little commercial importance, but it is frequently used as a study organism in behavioural ecology, and it has been traded in the aquarium industry to some extent. The adult life stage is well described, however its early life history is nearly unknown. This paper provides the first description of post-flexion larvae of A. maculatus, including detailed illustrations, photographs, morphological data, and collection site data of specimens collected during a multipurpose research survey conducted within the Sargasso Sea Subtropical Convergence Zone. The collection site also implies a geographic range expansion, off the continental shelf, of the pelagic larvae stage. This paper hence advances the scientific knowledge about the early life stages, distribution and ecology of this species.

In the present study, we assessed the sponge fauna, sponge-associated, and planktonic prokaryotic communities residing in Burgers' Zoo Ocean aquarium, Arnhem, the Netherlands. The Ocean aquarium consisted of separate displays and life support systems, and included fish-only systems in addition to a large, 750,000 L tank containing a living, tropical coral reef ecosystem. Sponges were observed throughout the aquarium system and were identified as belonging to the genera Chalinula, Chondrilla, Chondrosia, Cinachyrella, Stylissa, Suberites and Tethya. There was a highly significant difference in composition between sponge-associated and planktonic prokaryotic communities. The tanks in which the sponges were sampled appeared to have a secondary structural effect on prokaryotic composition with sponges and water from the same tanks sharing several microorganisms. Both sponge-associated and planktonic prokaryotic communities housed prokaryotic taxa, which were highly similar to microorganisms previously recorded in sponges or coral reef environments, including taxa potentially involved in nitrification, denitrification, sulphur oxidation, and antibiotic biosynthesis. Several abundant microorganisms were only recorded in sponges and these may play a role in maintaining water quality in the aquarium system. Potential pathogens, e.g. related to Photobacterium damselae, and beneficial organisms, e.g. related to Pseudovibrio denitrificans, were also detected. The present study showed that Burgers' Zoo Ocean aquarium housed diverse free-living and host-associated prokaryotic communities. Future research should focus on identifying conditions and microbial communities conducive to a healthy aquarium environment.

Small and medium pelagic fish (SMPF, i.e. Scomber colias, Trachurus spp, Sardina pilchardus, and Sardinella spp) in the Canary Islands are mainly targeted by the artisanal purse-seine fleet. The waters in the archipelago (located in the coastal transition zone of the Canary Current Eastern Boundary Upwelling System) are monitored since the late nineties by a hydrographic section (RAPROCAN) designed to study the temporal variability of the eastern subtropical gyre. In this study we analyse the relationship between the SMPF abundance assumed from official sale notes (reported since 2007) and several oceanographic parameters obtained for the outermost water layer (Sea Surface Temperature, SST, and concentration of chlorophyll a, Chla) and from the 200–800 m depth waters (Sea Temperature, ST_200–800, and salinity, Salinity_200–800). Except for SST, statistically significant correlations occur between environmental variables and SMPF landings when one-year time-lag is considered, matching with the time period necessary for these species to attain legal catchable sizes and, hence, being catchable by the fishery. However, in the GLM only Chla resulted a significant explaining variable for the SMPF landings during the following year, probably because this strong correlation overshadows the ST_200–800 influence. Keeping the monitoring systems is crucial to understand, foresee and anticipate potential variations in the fishery resources and to aim the sustainable exploitation of the SMPF populations, even more challenging in the current climate change scenario.

Harbour seals were extensively hunted in Denmark, but have only been driven to local extinction in one larger area, the South Funen Archipelago and Little Belt, where the species has been absent throughout the 20th century. Despite high growth rates of the Danish harbour seal populations after protection from hunting in 1976, seals have only been observed sporadically in the South Funen Archipelago and Little Belt until recent years, where recolonisation now causes conflicts with fisheries. Here, we review historical sources documenting the local extinction of harbour seals in the area during the 19th century and report the results of aerial surveys of haul-out sites during moulting seasons of 2021–2023 and pupping seasons of 2022 and 2023. Historical sources reveal that seal hunting was a common practice in southern Denmark, but catches dwindled to rarities during the 19th century. During recent surveys, seals were detected at six of the identified potential haul-out sites. Around Aarø Island, an average of 141 (range: 92–186) harbour seals were recorded over four moulting season surveys, constituting the majority (90%) of the total counts of the surveyed area. During the pupping seasons, a total of five pups was encountered at two different haulouts. As none of the haulouts are protected during the pupping and breeding seasons, protective measures may support this recolonisation of the historic harbour seal breeding range.

Understanding the relationships between cetaceans and their environment is crucial for conservation. This study examined humpback whales in Bahía de Banderas, Mexico, identifying key calving habitats. From 2018 to 2023, 1066 sightings were recorded, including 242 mother–calf groups, 109 mating groups, and 715 other groups. Spatial analysis revealed a non-random distribution; both the Kruskal–Wallis and Wilcoxon–Mann–Whitney tests detected significant differences (P < 0.05) in site preferences. Calving mothers favoured habitats with a mean depth of 59 m and a distance of 2 km from the coast, while mating groups preferred locations at 126 m and 4 km, and other groups chose areas at 149 m and 4 km. All groups were found in relatively flat areas around 2° seafloor slope. A dispersion test indicated a significant relationship between the location of calving mothers and environmental factors. K-means clustering showed 83.6% of calving mothers' sightings at depths less than 40 m and 2 km from the coast. Ensemble species distribution models identified three critical calving areas: one large area (261.8 km2) along the north coast and two smaller areas (9.5 and 5.4 km2) at the southern end of the bay. This study highlights Bahía de Banderas as a vital breeding habitat for humpback whales, providing insights for conservation strategies to protect calving grounds during the breeding season.

A single Stygiomedusa gigantea was caught by demersal crab trawl off Namibia at a fishing depth of 750 m. Although widely considered to be globally distributed in meso- and bathy-pelagic waters, this represents the first record of the species from the SE Atlantic and only the second from around Africa. The photographed specimen differs slightly from previous observations and attention is drawn to accurately recording future material.

Synthesising knowledge on the health of marine ecosystems and the human activities is crucial to informing holistic marine management. In many coastal states, however, research is conducted in an ad hoc manner and rarely compiled into accessible repositories making it challenging for marine managers to identify knowledge gaps when allocating resources. Here we conduct a structured review of existing literature to identify the current state of marine and coastal knowledge in the Isles of Scilly, an oceanic archipelago in the UK. The archipelago's marine flora and fauna are biogeographically unique in the Northeast Atlantic, with a distinct mosaic of warm and cold temperate habitats and species and are also considered a rare example of a near pristine marine environment in the otherwise highly degraded Northeast Atlantic Ocean. We found 150 sources relating to the marine biodiversity and relevant human activities in the Isles of Scilly with increasing diversification of research topics in recent years. Sources however remain dominated by specific taxa and habitats, suggesting the Isles of Scilly would particularly benefit from future research into: (1) anthropogenic impacts associated with warming waters and intense seasonal vessel activity; (2) development of repeatable survey protocols that can underpin long-term, ecosystem-based monitoring and management (notably for reef and sediment habitats and the European spiny lobster); and (3) data gaps associated with marine teleost fish and elasmobranch communities including identifying core habitat. This review can therefore act as a baseline biological synthesis for the region and importantly, can inform future research priorities.

Sea turtle populations have significantly declined in recent years due to anthropogenic causes. Historical stranding records in the Canary Islands archipelago (Spain) reveal a high frequency of Caretta caretta and Chelonia mydas strandings. Our study aims to comprehensively characterize and explore these stranding records. Additionally, we have investigated the interactions between sea turtles and the island's professional fishers, seeking insights from small-scale artisanal fishers to understand the current state of sea turtle populations. The results have shown that Tenerife stands out with the highest number of sea turtle strandings, recording 1875 strandings over a span of 23 years. The primary cause of sea turtle stranding's is the interaction with fishing gear, specifically nets and hooks. Moreover, our research has highlighted the need for improved knowledge and training on how to handle stranded sea turtles within the fishing sector. Consequently, raising awareness and implementing conservation plans for sea turtle populations in Tenerife is of outmost importance in addressing and improving the current situation.

The importance of habitat-forming species, particularly cold-water corals like Dendrophyllia ramea, cannot be overstated as they provide crucial physical structures that offer shelter, food, and breeding habitat for a range of other species. We studied the spatial distribution and abundance of D. ramea, its associated species and the impact of human activities in a population of the Herradura, Granada in the western Mediterranean. Video transects were conducted at different depths, and epibiont samples were collected to describe the coral assemblage and the diversity of associated organisms. Dendrophyllia ramea presented high abundances at an unusually shallow depth in the Mediterranean, ranging from 30 to 48 m, despite typically being found between 50 and 500 m, with recordings indicating occurrences as deep as 1000 m, and hosting a high number of epibionts and macro-benthic organisms associated with coral reefs. Bryozoans showed a close relationship with D. ramea as they are important components of both the reef and the epibiont community. This study identified 63 new species and 15 new genera associated with cold-water corals. This study showed the importance of D. ramea as a nursery site, even for other habitat-forming species. The major threat to this community is human activity (fishing, littering and free anchoring), with the most abundant types of waste being rubber, glass/ceramics, and plastic polymers, and many fishing lines and nets damaging the corals. Overall, this study emphasises the urgent need to protect cold-water corals and their associated species and reduce the impact of human activities on marine ecosystems.

Jellyfishes have ecological and societal value, but our understanding of taxonomic identity of many jellyfish species remains limited. Here, an approach integrating morphological and molecular (16S ribosomal RNA and cytochrome oxidase I) data enables taxonomic assessment of the blubber jellyfish found in the Philippines. In this study, we aimed to resolve doubt on the taxonomy of Acromitoides purpurus, a valid binomen at the time of our research. Our morphological findings confirm that this jellyfish belongs to the genus Catostylus, and is distinct from known species of the genus inhabiting the Western Pacific, such as Catostylus ouwensi, Catostylus townsendi, and Catostylus mosaicus. Detailed morphological and molecular analyses of the type specimens from the Philippines with the other Catostylus species revive the binomen Catostylus purpurus and invalidate A. purpurus. Genetic analysis also distinguishes this Philippine jellyfish from C. townsendi and C. mosaicus. Through this study, we arranged several Catostylidae taxa into species inquirendae (Catostylus tripterus, Catostylus turgescens, and Acromitoides stiphropterus) and one genus inquirenda (Acromitoides) and provided an identification key for species of Catostylus. This comprehensive study confirms the blubber jellyfish as C. purpurus, enriching our understanding of jellyfish biodiversity. The integration of morphological and genetic analyses proves vital in resolving taxonomic ambiguities within the Catostylidae family and in the accurate identification of scyphozoan jellyfishes.

Long-term marine monitoring programmes have provided numerous quantitative data on the composition of North Sea benthic communities and their changes over time, including species introductions. Particularly in the German Bight, the rapid environmental and hydrographical changes are promoting the spreading (usually anthropogenically mediated) of neobiota, with more than 150 species being registered to date. During routine seafloor monitoring, grab samples taken on the subtidal sandbank of the Borkum Reef Ground revealed the presence of the polychaete Streptosyllis nunezi in different years, a species previously unreported in the southern North Sea. In this paper, these individuals are described morphologically and the population status is discussed. Our finding demonstrates the importance of intensive and regular environmental monitoring programmes for the assessment of regional biodiversity and its potential changes.

Lough Hyne (LH) Marine Nature Reserve in Ireland is a globally recognised biodiversity hotspot that hosts mesophotic-like communities in shallow water, however, major changes have occurred to most of the rocky cliff (>6 m) communities in one or more events between 2010 and 2015. To provide insights into these changes, we compared the sponge assemblage composition on the undersides of different sized, shallow (<1 m) subtidal boulders between 2000 and 2022 at two sites in LH. We also measured sponge species richness at seven sites in 2018. We found that unlike earlier reports from the deeper subtidal reef sponge assemblages, there was no evidence for changes in sponge assemblage composition on the undersides of boulders at either site. We also found high levels of sponge species richness at all seven sites sampled in 2018. We did find differences in sponge assemblages between sites and for different boulder sizes, which we propose is a result of site-specific environmental conditions and disturbance and size–area relationships. Since we found no changes in the shallow subtidal sponge assemblages between 2000 and 2022, our results support the hypothesis that changes to the deeper subtidal sponge assemblages at LH are driven by local processes associated with deeper water in LH, potentially related to the seasonal oxythermocline that forms within LH. Given the national and global importance of LH, understanding the drivers of change is critical to determine if management actions can prevent any future alterations to the LH sponge assemblages and support wider mesophotic community management.

The morphology of female bopyrids is adapted to parasitism, but understanding the function of their thoracic and mouth appendages is hindered by their small size and cryptic lifestyle, limiting detailed examination. This study aimed to clarify the function of the first oostegites and maxillipeds in bopyrid isopods infesting the branchial chamber of caridean shrimp through behavioural observations and morphological examination. We tested whether the movement of these structures was exclusive to ovigerous female parasites during brood ventilation. The results revealed that the beating of the maxillipeds and flapping of the first oostegites were not restricted to ovigerous females. However, the frequency of these movements was significantly higher in ovigerous females than in non-ovigerous females. The frequency of maxilliped beating increased with embryonic development, whereas that of flapping the first oostegites exhibited the opposite trend. Microscopic observation using dye showed that the movements of the maxillipeds and the first oostegites expelled residual dye from the female brood chamber through the dorsal surface or beneath the first oostegites. The dye was then transported by the water current generated by the scaphognathite of the host shrimp. These findings suggest that these structures not only facilitate ventilation but also serve as a grooming mechanism for female parasites, which is critical for embryonic survival. The results of the present study represent the first observation of embryo grooming in bopyrid isopods. This study also provides new information on the functional morphology of bopyrid isopods, which is important for understanding their ecological dynamics and adaptation to parasitism.

Polynesia is a hotspot for marine biodiversity in the South Pacific Ocean, yet the distribution of many invertebrate taxa in this region is still often poorly assessed. Information on the diversity and phylogeography of sponges in particular remains limited in spite of their importance for coral reef ecosystems. Recent expeditions to the island group of Wallis and Futuna enabled the first larger-scale assessment of the Wallis Island sponge fauna, resulting in the molecular identification of 82 unique Molecular Operational Taxonomic Units (MOTUs) from 339 sponge samples based on 28S C-region rDNA and CO1 mtDNA data. Faunal comparisons with both adjacent archipelagos and more distant Indo-Pacific regions were predominantly based on the MOTUs obtained from Wallis Island ecoregions, and suggest high levels of endemism of sponges in Wallis and Futuna, corroborating previous data on the biodiversity of sponges and other marine phyla in the South Pacific. The results of this molecular taxonomic survey of the Wallis and Futuna sponge fauna aim to lay solid foundations for a sustainable ‘Blue Economy’ in Wallis and Futuna for the conservation of their local coral reefs.

Egg masses from an unknown mollusc have been found in South-West Iceland since 2020, but it was not until September 2023 that the adult organism was collected. Morphological analysis of both adults and egg masses pointed towards the identification of the species as Melanochlamys diomedea. This was further confirmed through DNA analyses using COI, H3, and 16S rRNA markers, which established the presence of a new non-indigenous species in the North Atlantic. Members of the genus Melanochlamys have predominantly been found in the Indo-Pacific basin and the Pacific Ocean, with only one species known to exist across the Madeira Islands, Canary Islands, and Cape Verde in the Atlantic. The known distribution range of M. diomedea extends from Alaska to California on the Pacific side of North America, where it typically inhabits sandy-muddy areas of the littoral in the tidal zone and below. It is not known how the species arrived in Iceland. However, maritime transport through either ballast water or biofouling is being considered as the most likely mode of dispersal.

We investigated how environmental conditions translate into reproductive success or failure in Aurelia aurita from the medusa to the polyp life stage. This study examined how: (i) settlement success and development of planula larvae and polyps vary across the year, (ii) the role of temperature in determining the successful settlement of larvae and growth of polyps, and (iii) the influence of maternal provisioning in the successful settlement of larvae and growth of polyps. Medusae were collected monthly from February to December 2019 from Horsea Lake, UK. Planula larvae were settled in conditions mimicking the in situ temperature and salinity of collection. For the individual treatments, planula collected in August settled most rapidly. Early development rates (<8 tentacles) were significantly higher than later growth rates (>8 tentacles) and were positively correlated with temperature, unlike later growth rates. Planula length, used as an indicator of maternal provisioning, varied significantly across the year. In July 2019, a high temperature anomaly coincided with an increased time spent by planula larvae in the water column. Increasing temperatures past thermal limits through the increasing occurrence of temperature anomalies is likely to be detrimental to larval settlement and indirectly to the replenishment of temperate polyp populations.

Diapterus brevirostris (Sauvage, 1879) is a fish of the family Gerreidae, native to the tropical and subtropical waters of the Pacific coast of America. A specimen of this species was captured off the coast of Asturias, Spain. To the best of our knowledge, this is the first record of the genus Diapterus in the North Atlantic. Given its small size (6.4 cm), it is likely that the species was present in the area for a relatively short time. Although the introduction pathway is unknown, the species' native area and the proximity of a major port to the site of capture suggest that ship's ballast water is the most likely vector of introduction.

Sponges are important components of marine systems globally, and while sponges have generally been shown to tolerate ocean acidification (OA), most earlier studies have focused on demosponges with siliceous skeletons. In contrast, little is known of how calcareous sponges, with calcite or aragonite skeletons, may react to OA conditions. Here we measured tissue necrosis and respiration rate of the temperate New Zealand calcareous sponge Grantia sp. to simulated OA. Our treatment conditions were based on the IPCC RCP8.5 (pCO2 1131.9 ± 113 μatm) scenario over a 28 day experiment, and responses were compared to current day control conditions (pCO2 512.59 ± 23 μatm). Sponge respiration rate was not significantly different between the control and treatment sponges and there was no evidence of tissue necrosis over the course of the experiment. Overall, our study is consistent with earlier studies on demosponges, showing calcareous sponges to be resilient to OA.

Bivalve molluscs are a diverse group of animals with particular economic and ecological importance. Their morphological characteristics frequently confuse their identification leading to mislabelling of edible species. Genetic diversity is critical to the resilience of marine bivalve populations in the face of environmental stressors such as ocean acidification and warming. In this study, we characterized the phylogeny and defined the first DNA barcodes of six marine bivalves [Ostrea edulis (Linnaeus, 1758) Arca noae (Linnaeus, 1758), Pinctada radiata (Leach, 1814), Venus verrucosa (Linnaeus, 1758), Calllista chione (Linnaeus, 1758) and Ruditapes decussatus (Linnaeus, 1758)] sampled from different coastal areas of Aegean and Ionian Seas using the molecular markers cytochrome c oxidase subunit I (COI) and 18S ribosomal RNA (18S rRNA). Further, COI gene was employed to investigate the population genetic diversity since 18S rRNA exhibited no conspecific differences. The sequence of 18S rRNA successfully discriminated the bivalves at family or superfamily level but occasionally proved insufficient for species identification. Contrariwise, COI was highly informative and could reliably distinguish all species. Population haplotype diversity was moderate to high and was always accompanied by generally low nucleotide diversity, indicating genetically closely related haplotypes. The invasive Pinctada radiata was found to be panmictic even among distant sampling areas, while Ostrea edulis was the only species that exhibited moderate levels of population subdivision. Finally, here we report for the first time the presence of Ostrea stentina in Thermaikos Gulf sampled among Ostrea edulis specimens, demonstrating a new invasive bivalve species in Eastern Mediterranean.

Here, we report the first sighting records of Bryde's whales in Nicaragua. Four sightings were made in 2022 during boat-based surveys off the southwestern coast of Nicaragua. Photo-identification, distributional data, dive times, and behavioural information were collected, and environmental parameters, including sea surface temperature, were measured for each sighting. Sightings included calf and non-calf groups displaying travelling (n = 1; 25%), milling (n = 1; 25%), and suspected feeding (n = 2; 50%) behaviours. Approximately 4 h of focal following allowed the calculation of short and long breath intervals. Based on our observations, the individuals were suspected of feeding in the area, based on the presence of feeding birds, feeding humpback whales, relatively high time-lagged chlorophyll-a, and observed general behaviours. Our findings indicate that this species may occasionally visit Nicaraguan coastal areas in search of feeding opportunities, and could represent a possible range extension of the Eastern North Pacific stock.