Emergent, conspicuous parasites on commercially valuable fishes have become an increasing concern for fisheries because they can impair host condition and markedly reduce marketability. Since 2022, fishermen and veterinary inspection services have reported a rising frequency of leeches attached mainly to the branchial cavity of fish in Galician waters (NW Spain), with a particularly high impact on the sedentary, shallow-water ballan wrasse Labrus bergylta , a key coastal fishery resource in the region. This study aimed to document and confirm the identity and biogeographic significance of these infestations and to provide molecular reference data for the causative taxon. Records were compiled through an informal fisheries information network using photographs and videos, and four L. bergylta specimens were examined. Parasites were identified as Trachelobdella lubrica (Grube 1840) based on the diagnostic characters described for the species. This constitutes the first confirmed record of T. lubrica in Galician waters and the northernmost confirmed Atlantic record, extending beyond previously Mediterranean-restricted European occurrences. The COI-5P sequence obtained from the T. lubrica sample is unparalleled in the BOLD and GenBank molecular repositories, representing the first barcode of this species publicy available to the scientific community. Given the species’ affinity for warm–temperate waters and documented regional sea-surface warming trend, the northward appearance of T. lubrica may indicate climate-linked distributional change. Targeted monitoring is recommended to track infestation dynamics, mitigate potential economic losses, and improve molecular resources for marine leech surveillance.

This study documents unusual pigmentation patterns in marine fishes from Spanish coastal waters and provides a global synthesis of published records of ambicolouration in wild flatfishes. A mixed pigmentation anomaly was recorded in Diplodus sargus (Sparidae), severe hypopigmentation compatible with oculocutaneous albinism was documented in Halobatrachus didactylus (Batrachoididae), and near-complete ambicolouration was observed in Solea senegalensis (Soleidae). Three additional unusual pigmentation patterns involving Labrus bergylta (Labridae) and D. sargus were documented photographically during underwater observations and are regarded as putative pigmentation anomalies because natural colour variation and physiological colour change cannot be excluded. The specimens were obtained opportunistically through fishery bycatch, scientific surveys and underwater observations conducted in Galicia and Andalusia between 2025 and 2026. DNA barcoding confirmed the species identity of the three collected specimens. The discovery of an ambicoloured Solea senegalensis prompted a review of this condition in wild flatfishes worldwide. The literature review identified 100 studies reporting ambicolouration in 79 wild flatfish species from 10 of the 19 recognized families. Pleuronectidae and Paralichthyidae contained the largest numbers and proportions of species with published records, although these patterns may be influenced by uneven research and reporting effort. Pigmentation anomalies, although uncommon in nature, have been associated with genetic, developmental or environmental processes, but their environmental significance cannot be determined from opportunistic records alone. Standardized long-term monitoring accompanied by population and environmental data would be required to assess their potential value in ecosystem assessment.

This study documents the presence of the antenna codlet Bregmaceros atlanticus Goode Bean, 1886 (Bregmacerotidae), in the Spanish waters of the Canary Islands. Three specimens were collected between 2012 and 2024. A comprehensive morphological description, accompanied by illustrations, confirms the accurate identification of this species. Employing an integrative taxonomic approach, a DNA barcode of the cytochrome c oxidase subunit I (COI) was obtained for one specimen, corroborating its morphological identification as Bregmaceros atlanticus. A molecular taxonomic analysis utilizing this marker revealed the existence of four clusters matching an equal number of Barcode Index Number (BINs) associated with specimens identified as Bregmaceros atlanticus. The examined voucher specimen assigns BIN AAV0298 to Bregmaceros atlanticus. This finding suggests that, contrary to previous assumptions, the species is exclusively distributed in the Atlantic Ocean.

This study documents the presence of two uncommon tetraodontiform fishes and reviews the occurrence of species from this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in the Atlantic waters off the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, while a specimen of Ephippion guttifer was captured in 2025 in the R & iacute;a de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of the two species. Histological reproductive analysis of the Ephippion guttifer specimen revealed a female in the spawning-capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. An updated comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations was compiled. Historically, a total of 26 species across five families have been reported in Spanish waters, with 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is included, providing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment.

Nine specimens of Cyttopsis rosea (Zeiformes: Parazenidae) were collected during scientific surveys at three different locations in the northeast Atlantic. All nine specimens were included in the molecular analysis, adding new cytochrome c oxidase subunit I sequences to public databases. Of these, six specimens were retained for detailed morphological examination. Morphological measurements and counts agree with previous descriptions and confirm the identification of C. rosea. However, molecular species delimitation analyses suggested cryptic diversity, identifying three molecular operational taxonomic units, contrary to the current status of a single species with a worldwide distribution. The integration of classical and molecular taxonomy proved essential for accurately delimiting and characterizing this species, enhancing our understanding of its intraspecific morphological and molecular variability. A literature review of the available morphological data of Cyttopsis rosea between Atlantic and Pacific specimens showed differences in the caudal peduncle length, number of vertebrae and the number of scales in the lateral line, which could support the existence of different species. Based on the resulting data and the available literature, an updated key of the accepted members of the family Parazenidae is provided.

The genus Taeniurops comprises two valid species within the family Dasyatidae: Taeniurops grabatus (Geoffroy Saint-Hilaire, 1817) and Taeniurops meyeni (Müller Henle, 1841). This paper reports the first record of a specimen of Taeniurops grabatus caught in trammel nets at a depth of 3 m in Galician waters (north-west Spain). We provide a comprehensive morphological description and illustrations of the specimen, a female with a total length of 1740 mm and a weight of 62.5 kg. In addition, molecular analysis has provided a new COI DNA barcode sequence, which has now been added to the molecular repositories. This specimen represents the northernmost documented occurrence of the species in the Atlantic Ocean. We discuss the range of the species based on the existing literature, noting that Taeniurops grabatus is a thermophilic or tropical affinity species. Its presence in the northern Iberian Peninsula is likely a consequence of range shifts of fish species due to climate change or transgression of subtropical waters.

A taxonomic characterisation of Enchelyopus cimbrius (Gadiformes, Gaidropsaridae) is presented on the basis of 11 specimens from the North Atlantic. Identification was carried out by integrative taxonomy, combining the examination of morphological and molecular characters. The former are consistent with previous descriptions, but new biometric and meristic data for the species are provided, showing ontogenetic changes with respect to post-larvae-pelagic juveniles. Length–weight relationships of 44 specimens showed isometric growth, while the length-length relationships of eight body parts of the species showed differential allometric growth. The molecular analysis resulted in the addition of 11 new sequences of cytochrome c oxidase subunit 1 (COI) to the molecular repositories. DNA barcoding supports the morphological identification of Enchelyopus cimbrius specimens and confirms the amphi-Atlantic distribution of the species. Updating the taxonomic data can be useful to confirm the current status or to identify divergences and also to better characterise and delimit each species, contributing to a better understanding of intraspecific variability, both morphological and molecular.

This study reports the first record of Lyconus brachycolus in Spanish waters. A single specimen measuring 216 mm in total length was captured on 13 October 2024 in the Cantabrian Sea (north of Spain, 43.8467 N, −6.2109 W) by bottom trawl at a depth of 412 m. A detailed morphological description, updated characteristics, and illustrations are provided. For comparative purposes, an update of the species’ morphological characteristics was carried out. In an integrative taxonomic approach, the DNA barcode was obtained, which confirmed the morphological identification of the specimen as Lyconus brachycolus. A molecular taxonomic analysis using this marker showed the existence of two clades separated by 5.1%, corresponding to Lyconus brachycolus and Lyconus pinnatus, the two currently valid species of the genus.

Barathronus is a genus of blind cusk eels comprising 11 valid species. In this paper, we report the second specimen ever documented of Barathronus roulei (Bythitidae) obtained from the Porcupine Bank by R.V. Vizconde de Eza using a bottom trawl at a depth of 1349 m. Morphological description and illustrations, including a radiograph, are provided. In addition, three new sequences corresponding to three different genes, cytochrome c oxidase subunit I (COI)-DNA barcoding, 16S ribosomal RNA (16S), and recombination activating protein 1 (RAG1), have been added to the molecular repositories, representing the first sequences for the species.

Notacanthid fishes constitute a common part of benthopelagic deep-sea fish communities on seamounts and continental slopes around the world. However, their highly conserved morphology and the usual lack of information on deep-water organisms make it difficult to appropriately address their biodiversity. A multidisciplinary approach combining morphological data with a DNA-based species delimitation analyses was used to explore the taxonomy of Notacanthus species. For this purpose, morphological and molecular data were obtained from 43 individuals, and the resulting information was combined with the available data. The results showed the occurrence of Notacanthus arrontei n. sp. from the Iberian Peninsula and highlighted several taxonomic conundrums regarding the Notacanthus genus. For instance, no significant differences were found between Notacanthus indicus and the recently described Notacanthus laccadiviensis, questioning its taxonomic status. Similarly, the result of the species delimitation molecular analysis coincided with previous DNA barcoding studies supporting the snubnosed spiny eel Notacanthus chemnitzii as a species complex that requires further research. Moreover, two unidentified records from the Indian Ocean were confirmed to belong to an unknown species pending formal description, and barcoding data show for the first time the occurrence of the shortfin spiny eel Notacanthus bonaparte in the Australia-New Zealand area. This research confirms the existence of important gaps in the knowledge of notacanthid fishes and represents a step forward toward a better understanding of their biological diversity.

ABSTRACT The Argonautoidea is a monophyletic superfamily of pelagic incirrate octopods primarily distinguished by an unusual means of copulation where a sexually modified arm, or hectocotylus, is detached and transferred from dwarf males to the female. Males of the seven-arm octopus Haliphron atlanticus are scarcely observed and little is known about their reproductive strategy. A detailed description of H. atlanticus digestive system, hectocotylus morphology, histology and functioning was carried out with fresh and preserved material from two males captured in the Bay of Biscay (North Atlantic). It is the first time that a hydrostatic sac/swimbladder in the anterior region of the intestine is described in an argonautoid male. Investing in reproductive rather than somatic growth is evident in the dwarf males of H. atlanticus, which lack the Needham sac and the terminal organ. Functionally, these organs have been replaced by two external modifications at the distal end of the detachable hectocotylus: a spermatophore reservoir with a single long spermatophore and a muscular penis, both essential to ensure fertilization once the hectocotylus is detached from the dwarf males. Haliphron has been considered a monospecific genus, with a single species distributed around the world. However, mitochondrial genetic analysis (cytochrome c oxidase subunit I and 16S ribosomal RNA) supports the existence of at least two species of Haliphron, one in the northern Atlantic and another in the southern Atlantic/Pacific. Further genetic and morphological studies are needed to unravel the diversity of this oceanic octopod family.

The Galician coast, with 1498 km of shoreline, is located in the northwest corner of the Iberian Peninsula. This area is the northern boundary of the Canary upwelling system, at the transition between the subtropical and subpolar regimes of the North Atlantic, which makes it of particular interest for the detection of marine ecosystem changes. Relationships between the occurrence of non-native marine fishes in this coastal area and sea surface temperature fluctuations are investigated. Information about fish species were collected from published and unpublished material recorded since 1945, and with regular monitoring data since 1983. A total of 50 new additions to the Galician marine ichthyofauna were recorded over the period 1945-2022. One of these species, Cynoscion regalis (Sciaenidae), is considered an introduced species. Most of the remaining 49 species are the result of latitudinal range expansions, including 15 species that have reached the northern limit of their distribution in the north-east Atlantic. This evidence points towards the tropicalization of the Galician fish fauna. Satellite sea-surface temperatures over the period 1982-2020 showed that Galician oceanic and coastal waters are, respectively, 0.78 +/- 0.01 degrees C and 0.32 +/- 0.01 degrees C warmer than 40 years ago. This ocean warming, added to the high productivity of the area and the oceanographic features, support the different ranges of expansion found in marine fishes, reinforcing the process of tropicalization. The increasing presence of new marine fishes in Galician waters could lead to relevant impacts on this ecosystem, like the emergence of new fish parasites and the increase of top predators and herbivorous fish among others.

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.

The occurrence of a small specimen of Brosme brosme (Gadiformes: Lotidae) from the Porcupine Bank is reported. A single specimen with a total length of 73.2 mm was caught with bottom trawl at a depth of 322 m depth in 2017. The specimen was identified morphologically and confirmed by molecular taxonomy using DNA barcoding. Based on the size and ontogenetic characters found, the specimen was identified as a post-larval individual, and a pelagic habitat of the specimen seems more likely.

Lepidion lepidion and Lepidion eques are two nominal species of the genus Lepidion (Moridae) from the Mediterranean Sea and the North Atlantic Ocean, respectively. Following the publication of the latter species, several authors highlighted the morphological similarities between them, questioning their taxonomic relationship. Despite these reasonable doubts, the two species have long been considered as valid and separate species. Since the 2010s, a series of integrative studies, combining morphological and molecular analyses, have demonstrated that L. eques is a junior synonym of L. lepidion. However, the former has continued to be used inconsistently in biodiversity databases and ichthyological literature. Thus, while the “Catalog of fishes” immediately incorporated this new status, the databases “FishBase” and “WoRMS” did not, maintaining the validity of both species. Consequently, in the scientific literature, only a few authors adhere to the synonymy relationship, naming the Atlantic species as L. lepidion, while most maintain the older nomenclature of L. eques. These two nominal species represent an interesting case study on the application of taxonomic nomenclature and how the different criteria for incorporating new species affect the scientific community.

The occurrence of a small specimen of Lepidion guentheri (Giglioli, 1880) (Gadiformes: Moridae) with an unusual dark colouration in the Porcupine Bank is reported. A single specimen of 114.2 mm of total length was caught in 2023 in a bottom trawl at a depth of 1168 m. The specimen was initially identified morphologically and later confirmed by molecular taxonomy using DNA barcoding. Its dark colouration pattern is discussed in the context of the known colouration patterns. Although a complete melanosis is possible, ontogenetic colouration is proposed as the most likely cause. DNA barcoding suggests the presence of Lepidion guentheri in the southern Indian and southwestern Pacific Oceans.

Previous studies have highlighted possible cryptic biodiversity in the genus Neoscopelus. This hypothesis was tested using new morphological, molecular and biogeographical data on species of this genus caught in the north Atlantic between 2010 and 2022. The information obtained has been combined with available data in an integrative approach, including a review of morphological characters reported in the ichthyological literature and DNA-based species delimitation analyses. The main outcome of the present study is the description of Neoscopelus serranoi sp. nov. from the Atlantic and southwestern Indian Oceans. The new species is morphologically very similar to Neoscopelus microchir from which differs in having a shorter anal-fin base, a shorter pelvic fin, more dorsal and pectoral-fin rays, less anal-fin rays, fewer gillrakers and fewer isthmus and lateral photophores. They also differ in geographic distribution, with the new species occurring in the Atlantic Ocean and the near southwestern Indian Ocean, whereas N. microchir was originally described from Japanese waters of the Pacific Ocean. A literature review of available morphological data between geographic areas for Neoscopelus macrolepidotus and Neoscopelus microchir showed a large intraspecific overlap and no boundaries. However, molecular species delimitation based on the mitochondrial COI gene revealed the existence of cryptic diversity in both species, with eight to ten molecular operational taxonomic units (MOTU), compared to three valid species. Neoscopelus serranoi sp. nov. was considered an independent MOTU in all analyses performed, supporting the morphological identification as a new species. These results highlight that the taxonomy of Neoscopelus is far from settled and show that a greater sampling effort is needed to resolve the uncertainties and to describe unknown putative species. This also exemplifies the virtues of integrative taxonomy in delving into the systematics of deep-sea fishes.

A taxonomic revision of Anoplogaster cornuta (Trachichthyiformes, Anoplogastridae) based on specimens from the western North Atlantic is presented. Nineteen specimens were captured on Flemish Cap, western North Atlantic, by scientific surveys. Identification was carried out by integrative taxonomy, combining examination of morphological and molecular characters (DNA barcoding). Morphological examination confirmed several hitherto questionable taxonomic characters of the species, such as the presence of 8–9 branchiostegal rays and 3–5 fang-like teeth on the lower jaw. As a result of the molecular analysis, 19 new sequences of cytochrome c oxidase subunit 1 COI were added to molecular repositories. DNA barcoding supports the morphological identification of the specimens of A. cornuta from the western North Atlantic, and it also confirms the current status of a single species with a worldwide distribution. The combination of classical and molecular taxonomy has been useful for the delimitation and characterization of this deepwater species, contributing to a better understanding of its intraspecific morphological and molecular variability.

Fifteen specimens representing nine species of ceratioid fishes (Lophiiformes: Ceratioidei) were caught in Flemish Cap and Grand Banks of the western North Atlantic: Ceratias holboelli Krøyer, 1845 (Ceratiidae), Melanocetus murrayi Günther, 1887 (Melanocetidae), Leptacanthichthys gracilispinis (Regan, 1925), Dolopichthys karsteni Leipertz Pietsch, 1987, Dolopichthys pullatus Regan Trewavas, 1932, Oneirodes eschrichtii Lütken, 1871, Oneirodes macrosteus Pietsch 1974 and Oneirodes carlsbergi (Regan Trewavas, 1932) (Oneirodidae), and Linophryne cf. brevibarbata Beebe, 1932 (Linophrynidae). Identification was carried out by means of integrative taxonomy, combining the examination of morphological and molecular characters (DNA barcoding). The analysis showed two morphological types of D. pullatus distinguishable by the shape and morphology of the esca and the number and size of the teeth. The occurrence of Oneirodes carlsbergi represents the northernmost record in the western Atlantic. As results of the molecular analysis, 15 new ceratioid sequences were added to molecular repositories, two of them, O. carlsbergi and Linophryne cf. brevibarbata for the first time. The comparison of some nucleotide sequences shows new relationships between the genera Bertella and Dolopichthys, and also makes it possible to correct some of the erroneous assignments made in the databases. The combination of classical and molecular taxonomy has been useful for the delimitation and characterisation of these ceratioid species, contributing to a better understanding of their distribution and inter- and intraspecific variability.