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Deep-pelagic fishes are among the most abundant vertebrates on Earth. They play a critical role in sequestering carbon, providing prey for harvestable fishing stocks and linking oceanic layers and trophic levels. However, knowledge of these fishes is scarce and fragmented, hampering the ability of both the scientific community and stakeholders to address them effectively. While modelling approaches incorporating these organisms have advanced, they often oversimplify their functional and ecological diversity, potentially leading to misconceptions. To address these gaps, this synthesis examines the biodiversity and ecology of global deep-pelagic fishes. We review pelagic ecosystem classifications and propose a new semantic framework for deep-pelagic fishes. We evaluate different sampling methods, detailing their strengths, limitations and complementarities. We provide an assessment of the world's deep-pelagic fishes comprising 1554 species, highlighting major groups and discussing regional variability. By describing their morphological, behavioural and ecological diversity, we show that these organisms are far from homogeneous. Building on this, we call for a more realistic approach to the ecology of deep-pelagic fishes transitioning between very different ecological niches during diel vertical migrations. To facilitate this, we introduce the concept of 'diel-modulated realised niche' and propose a conceptual model synthesising the multiple drivers responsible for such transitions., (© 2024 John Wiley & Sons Ltd.)

The connection between epipelagic and deep-sea mesopelagic realms controls a variety of ecosystem processes including oceanic carbon storage and the provision of harvestable fish stocks. So far, these two layers have been mostly addressed in isolation and the ways they connect remain poorly understood. Furthermore, both systems are affected by climate change, exploitation of resources, and increasing pervasion of pollutants. Here we use bulk isotopes of δ 13 C and δ 15 N of 60 ecosystem components to evaluate the trophic linkage between epipelagic and mesopelagic ecosystems in warm oligotrophic waters. Additionally, we we conducted a comparison of isotopic niche sizes and overlaps across multiple species to evaluate how environmental gradients between epipelagic and mesopelagic ecosystems shape ecological patterns of resource use and competition between species. Our database comprises siphonophores, crustaceans, cephalopods, salpas, fishes, and seabirds. It also includes five zooplankton size classes, two groups of fish larvae, and particulate organic matter collected at different depths. Through this wide taxonomic and trophic variety of epipelagic and mesopelagic species, we show that pelagic species access resources originating from different food sources, mostly autotrophic-based (epipelagics) and microbial heterotrophic-based (mesopelagics). This leads to a sharp trophic dissimilarity between vertical layers. Additionally, we show that trophic specialization increases in deep-sea species and argue that food availability and environmental stability are among the main drivers of this pattern. Finally, we discuss how the ecological traits of pelagic species highlighted in this study can respond to human impacts and increase their vulnerability in the Anthropocene., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A new species of the hagfish genus Eptatretus (Myxinidae) is described based on two specimens (407-433 mm total length) collected off the northern Bahamas, between depths of 910 and 1153 m. The new species is distinguished from its congeners by having seven pairs of gill apertures well-spaced and arranged in a near straight line, a 3/2 multicusp pattern of teeth, 10-11 anterior unicusps, 50-51 total cusps, 12-14 prebranchial pores, 48-52 trunk pores, 79-84 total pores, and no nasal-sinus papillae. An identification key for the species of Eptatretus from the western Atlantic Ocean is also provided., (© 2023 Fisheries Society of the British Isles.)

Plastic debris is ubiquitous in the hydrosphere. Yet, we lack an understanding of contamination among deep-sea species and primarily how each trait can influence microplastic intake. We investigated microplastic contamination in the digestive tract of hyper-abundant mesopelagic lanternfishes (n = 364 individuals) from the Southwestern Tropical Atlantic, captured from 90 to 1000 m depth. Overall, microplastics were detected in most individuals analysed (frequency of occurrence = 68 %). Large microplastics, mostly of a filamentous shape were the most frequent, followed by smaller fragments and foams. Microplastics made of high-density polymers (PET, PVC, PA, SBR rubber) were more prevalent than low-density ones (PE, EVA and PBD rubber), especially under deeper layers. Larger microplastics were detected in lanternfishes captured off the northeastern Brazilian coast (mean 0.88 ± SE 0.06 mm) compared to those from around the Rocas Atoll and Fernando de Noronha Archipelago (0.70 ± 0.07 mm; p≤ 0.05), ∼350 km from the continent. Moreover, lanternfishes that migrate from the upper mesopelagic (200-500 m) to the epipelagic layers (<200 m) had simultaneously the highest intake and the smallest particles (1.65 ± 0.17 particles individual -1 and 0.55 ± 0.07 mm; p≤ 0.05). Biological mediated transport of microplastics from the epipelagic to the mesopelagic waters was evinced, but fishes foraging in shallower layers had the lowest intake (1.11 ± 0.10 part. ind. -1 ; p≤ 0.05). Furthermore, the jaw length was positively associated with an increment in microplastic intake (Incidence Rate Ratio = 1.1; p≤ 0.05). The lanternfishes that preferably prey upon fish larvae are more prone to microplastic intake than their counterparts, which forage mostly on crustaceans and gelatinous zooplankton (p≤ 0.05)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications., (© 2022 The Ecological Society of America.)

Here we report on new data on the occurrence and distribution of rare deep-sea fishes (Teleostei) collected from off north-eastern Brazil, including seamounts and oceanic islands of the Fernando de Noronha Ridge (Rocas Atoll and Fernando de Noronha Archipelago). Collections were made by the French RV Antea during the ABRACOS (Acoustics along the BRAzilian COaSt) expeditions between 29 September and 21 October 2015, and 9 April and 10 May 2017. Occurrences of Photostylus pycnopterus (Alepocephalidae), Gigantura chuni (Giganturidae), Ahliesaurus berryi (Notosudidae), Benthalbella infans, Rosenblattichthys hubbsi, Scopelarchoides danae (Scopelarchidae), Scopelengys tristis (Neoscopelidae), Zu cristatus (Trachipteridae), Stylephorus chordatus (Stylephoridae) and Pseudoscopelus cordilluminatus (Chiasmodontidae) are reported for the first time or confirmed in the Brazilian Exclusive Economic Zone. Photostylus pycnopterus and G. chuni are also recorded for the first time in the western South Atlantic, whereas records of P. cordilluminatus are the first in the western Atlantic. Other records of rare species of those families are also reported and discussed., (© 2022 Fisheries Society of the British Isles.)

Microplastics (MPs; <5 mm) are a macro issue recognised worldwide as a threat to biodiversity and ecosystems. Widely distributed in marine ecosystems, MPs have already been found in the deep-sea environment. However, there is little information on ecological mechanisms driving MP uptake by deep-sea species. For the first time, this study generates data on MP contamination in mesopelagic fishes from the Southwestern Tropical Atlantic (SWTA) to help understand the deep-sea contamination patterns. An alkaline digestion protocol was applied to extract MPs from the digestive tract of four mesopelagic fish species: Argyropelecus sladeni, Sternoptyx diaphana (Sternoptychidae), Diaphus brachycephalus, and Hygophum taaningi (Myctophidae). A total of 213 particles were recovered from 170 specimens, and MPs were found in 67% of the specimens. Fibres were the most common shape found in all species, whereas polyamide, polyethylene, and polyethylene terephthalate were the most frequent polymers. The most contaminated species was A. sladeni (93%), and the least contaminated was S. diaphana (45%). Interestingly, individuals caught in the lower mesopelagic zone (500-1000 m depth) were less contaminated with MPs than those captured in the upper mesopelagic layer (200-500 m). Our results highlight significant contamination levels and reveal the influence of mesopelagic fishes on MPs transport in the deep waters of the SWTA., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

In this study, a new species of Pseudogilbia Møller, Schwarzhans & Nielsen 2004 is described based on two male specimens (40-44 mm L S ) from shallow reefs of Bahia, Brazil. Pseudogilbia australis sp. nov. is distinguished from its only congener, Pseudogilbia sanblasensis Møller, Schwarzhans & Nielsen 2004 from Caribbean Panama, by having: two lower preopercular pores (vs. one); dorsal-fin rays 65-67 (vs. 69); anal-fin rays 51-53 (vs. 56); pectoral-fin rays 18 (vs. 20); caudal vertebrae 27-28 (vs. 30); pectoral-fin length 15.0%-15.9% L S (vs. 14.3); pelvic-fin length 13.5% L S (vs. 16.4) and a different morphology of the male copulatory organ. Pseudogilbia australis sp. nov. is the only dinematichthyid so far recorded in the South Atlantic. An updated diagnosis for the genus is also provided., (© 2021 Fisheries Society of the British Isles.)

Mesopelagic fishes are numerically the most important vertebrate group of all world's oceans. While these species are increasingly threatened by anthropogenic activities, basic biological knowledge is still lacking. For instance, major uncertainties remain on the behaviour, ecology, and thus functional roles of mesopelagic micronektivores, particularly regarding their interactions with physicochemical features. Here, we examine the trophic ecology, habitat, and migratory behaviour of the viperfish (Chauliodus sloani)-a poorly known and abundant deep-sea species-to further understand the ecology and thus functional role of mesopelagic micronektivores. Moreover, we explore how physical drivers may affect these features and how these relationships are likely to change over large oceanic areas. The viperfish heavily preys on epipelagic migrant species, especially myctophids, and presents spatial and trophic ontogenetic shifts. Temperature restricts its vertical distribution. Therefore, its trophodynamics, migratory behaviour, and functional roles are expected to be modulated by the latitudinal change in temperature. For instance, in most tropical regions the viperfish stay full-time feeding, excreting, and serving as prey (e.g. for bathypelagic predators) at deep layers. On the contrary, in temperate regions, the viperfish ascend to superficial waters where they trophically interact with epipelagic predators and may release carbon where its remineralization is the greatest.

A new species of Acropomatid fish, Verilus costai sp. nov., is described from a single locality off Belmonte, State of Bahia, Brazil. It resembles Verilus pseudomicrolepis (Schultz, 1940) from the Caribbean Sea. The two are considered vicariant and they are interpreted to be separated from other species of the genus Verilus by (amongst other characters) the presence of fangs on the dentary (vs. only villiform teeth), the anal fin formula (II+9 vs. III+7) and the naked occiput (vs. scaled). However, formal establishment of a separate genus is postponed until a complete phylogenetic review of the family has been performed. Verilus costai can be distinguished from V. pseudomicrolepis by its higher number of gill rakers (27-31 vs. 21-25), lower number of pseudobranchial filaments (15-23 vs. 21-28), shorter snout length (8.2-11.3 vs. 11.3-13.4 % of SL), and more compressed otoliths (OL:OH = 1.3-1.35 vs. 1.35-1.5). In addition, the fossil otolith-based species Verilus mutinensis (Bassoli, 1906) from the late Miocene to middle Pleistocene of the Mediterranean is thought to be related and indicates that in the past this group was more widely distributed than nowadays and comprised more vicariant species.

This study reports on the first record of the intermediate scabbardfish Aphanopus intermedius in the western South Atlantic Ocean, based on a single specimen 725 mm standard length collected between 0 and 610 m depth around Rocas Atoll off north-eastern Brazil. Measurements and counts are provided and compared with those available in the literature., (© 2018 The Fisheries Society of the British Isles.)

The present study reports the occurrence of the bearded brotula, Brotula barbata, in four different localities off southern Brazil. These records extend the species' known distribution limit southwards, beyond Rio de Janeiro, to the state of Rio Grande do Sul (30° 50' S). Morphometric and meristic data for the specimens reported herein are provided and discussed., (© 2018 The Fisheries Society of the British Isles.)

The freshwater and marine fish faunas of South America are the most diverse on Earth, with current species richness estimates standing above 9100 species. In addition, over the last decade at least 100 species were described every year. There are currently about 5160 freshwater fish species, and the estimate for the freshwater fish fauna alone points to a final diversity between 8000 and 9000 species. South America also has c. 4000 species of marine fishes. The mega-diverse fish faunas of South America evolved over a period of >100 million years, with most lineages tracing origins to Gondwana and the adjacent Tethys Sea. This high diversity was in part maintained by escaping the mass extinctions and biotic turnovers associated with Cenozoic climate cooling, the formation of boreal and temperate zones at high latitudes and aridification in many places at equatorial latitudes. The fresh waters of the continent are divided into 13 basin complexes, large basins consolidated as a single unit plus historically connected adjacent coastal drainages, and smaller coastal basins grouped together on the basis of biogeographic criteria. Species diversity, endemism, noteworthy groups and state of knowledge of each basin complex are described. Marine habitats around South America, both coastal and oceanic, are also described in terms of fish diversity, endemism and state of knowledge. Because of extensive land use changes, hydroelectric damming, water divergence for irrigation, urbanization, sedimentation and overfishing 4-10% of all fish species in South America face some degree of extinction risk, mainly due to habitat loss and degradation. These figures suggest that the conservation status of South American freshwater fish faunas is better than in most other regions of the world, but the marine fishes are as threatened as elsewhere. Conserving the remarkable aquatic habitats and fishes of South America is a growing challenge in face of the rapid anthropogenic changes of the 21st century, and deserves attention from conservationists and policy makers., (© 2016 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of The Fisheries Society of the British Isles.)

The Stephanoberycoidei includes 23 genera and c. 94 species of deep-sea teleosts commonly known as bigscales, pricklefishes, gibberfishes and whalefishes. Stephanoberycoidei is one of the least known groups of deep-sea fishes, in spite of their apparent relative abundance in meso and bathypelagic depths. Nine species of the Stephanoberycoidei are reported here for the first time in Brazilian waters, and most of them represent new range extensions for the south-western Atlantic Ocean. Those species are Melamphaes polylepis, Melamphaes typhlops, Poromitra sp. and Scopeloberyx robustus (Melamphaidae), Acanthochaenus luetkenii and Stephanoberyx monae (Stephanoberycidae), Rondeletia bicolor and Rondeletia loricata (Rondeletiidae) and Gyrinomimus sp. (Cetomimidae). Occurrences of the pricklefish Scopelogadus mizolepis (Melamphaidae), the gibberfish Gibberichthys pumilus (Gibberichthyidae) and the velvet whalefish Barbourisia rufa (Barbourisiidae) are confirmed in the Brazilian exclusive economic zone, but previously published records of Poromitra capito and Melamphaes simus (Melamphaidae) in the region most likely represent misidentifications. Validities of the recently described Poromitra kukuevi and Poromitra indooceanica are discussed in light of new specimens of the genus collected in the south-western Atlantic Ocean. An identification key for the 13 species of Stephanoberycoidei reported off Brazil is also provided., (© 2014 The Fisheries Society of the British Isless.)

The first record of the Cape hagfish Myxine capensis in Mozambican waters is reported based on a single 356 mm total length specimen taken by bottom trawl off Maputo, 25° 52·9' S; 34° 42·7' E - 25° 54·1' S; 34° 41·0' E, at depths from 557 to 564 m. This account also represents the northernmost record of a hagfish in the western Indian Ocean. Morphometric and meristic data are provided and compared with those of 27 specimens (including the holotype) caught off Namibia and South Africa., (© 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.)

The distribution limits in the Atlantic of Callorhinchus callorynchus (Callorhinchidae) and Odontesthes argentinensis (Atherinopsidae) are extended northwards to 22° 22' S and 22° 31' S, respectively, whereas that of Lile piquitinga (Clupeidae) is extended southwards to 22° 22' S. Their occurrence in the north of Rio de Janeiro State is discussed. Remarks on the osteology of O. argentinensis, and morphometric and meristic data of L. piquitinga, are also provided., (© 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.)

A new species of seven-gilled hagfish Eptatretus astrolabium (Myxinidae) is described from a 400 mm total length female trapped 1 km east from Planet Rock, Astrolabe Bay, Papua New Guinea, at c. 500 m depth. This is the first hagfish species reported from the waters around New Guinea. It can be distinguished from other hagfishes by a combination of characters including seven pairs of gill apertures, three-cusp multicusps on the anterior and posterior rows of cusps, 10 posterior unicusps, 52 total cusps, 18-19 prebranchial pores, five branchial pores, 48-49 trunk pores, 83-84 total pores and no nasal-sinus papillae., (© 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.)

This paper revises and updates taxonomic and distributional information about hagfishes (Myxinidae) from Australia. It covers five species of the genus Eptatretus: Eptatretus cirrhatus known from eastern Australia and also distributed around New Zealand, Eptatretus longipinnis endemic to South Australia, Eptatretus strahani originally described from the Philippines and reported here as a new record from Western Australia and two new species described herein as Eptatretus alastairi and Eptatretus gomoni, both from Western Australia. Eptatretus alastairi is distinguished from all congeners by the unique combination of the following characters: six pairs of gill pouches; three-cusp multicusps on the anterior and posterior rows of cusps; anterior unicusps 9-12; posterior unicusps 8-11; total cusps 48-56; prebranchial pores 13-16; branchial pores 5-6; trunk pores 50-55; tail pores 11-13; total pores 83-88; two bilaterally symmetrical nasal-sinus papillae in the dorsal surface of the nasal sinus. Eptatretus gomoni is distinguished from all congeners by the unique combination of the following characters: eight pairs of gill pouches; three-cusp multicusps on the anterior and two-cusp multicusps on the posterior row of cusps; anterior unicusps 10-11; posterior unicusps 9-10; total cusps 50; prebranchial pores 12-13; branchial pores 7-8; trunk pores 57-58; tail pores 14-15; total pores 91-93; no nasal-sinus papillae. An identification key for the Australian species of Eptatretus is also provided., (© 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.)

New host and geographical records are reported for the nematode Lappetascaris lutjani Rasheed, 1965, parasitizing the marine fish Trachipterus arawatae Clark, 1881 in Brazilian waters. Morphometric data and illustrations of the parasites are included.