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Accurate, gear-specific data is essential for fisheries management to quantify fishing pressure and ecosystem impacts, particularly in multi-gear fleets. In this study, we used electronic logbooks and sales notes from 2014 to 2023 to analyze the Portuguese multi-gear coastal fleet, obtaining information at a haul level. The objective was to identify and validate métiers down to level 6 according to the European Commission's definition (a combination of gear specifications, target species, fishing area, and season). This fleet comprises approximately 500 vessels using various types of traps, nets, and longlines to catch around 200 species of fish and invertebrates. We identified 28 métiers across six main gear types. The most representative métier is the octopus (Octopus vulgaris) trap fishery, followed by the European hake (Merluccius merluccius) gillnet and the black scabbardfish (Aphanopus carbo) longline fisheries. A strong association was found between most métiers and variables such as fishing season, fishing area, depth, and sediment type. Traps and nets were mostly used in the northwest area, in mixed sediments or sand, whereas longlines were mostly operated in the central west area, in steeper slopes on sandy and rocky bottoms. The study highlights the complexity of quantifying gear-specific fishing effort in multi-gear fisheries, where technical interactions occur, and competitive relationships exist between different fishing fleets and gears that exploit the same fish stocks.

Accurate species identification is crucial for effective fisheries management, particularly for cryptic species with overlapping ranges and similar morphologies. This study explores the coexistence and distribution of Aphanopus carbo and Aphanopus intermedius in the northeastern Atlantic over four decades using otolith contour analysis. Otolith samples were collected from Madeira and the African coast between 1990 and 2021 and analyzed using a wavelet-based method, which improves species discrimination by capturing finer morphological details. The analysis revealed stable species proportions over time, with A. carbo generally dominating the catches ( ~ 55–60%), except in 2010 when a decline was observed. A higher presence of A. intermedius in offshore areas may be associated with increased salinity near Madeira Island during the spawning season (October–December). Environmental changes, including variations in temperature and salinity at depths greater than 800 m, and the progressive expansion of the drifting longline fishery to new grounds, likely influenced these patterns. This study demonstrates that combining otolith contour analysis with genetically identified reference specimens enhances species discrimination and provides valuable insights into population dynamics and habitat use. These findings contribute to more effective fisheries management and stock assessments for these economically important scabbardfish in the northeastern Atlantic.

In this study, a single specimen of Pacific black scabbardfish Aphanopus arigato Parin, 1994 was collected at a depth of ~500 m near Dongsha Island in southwestern Taiwan (18°49′ to 20°45′N and 112°46′ to 116°15′E), on 14 March 2023. This is the southernmost record of A. arigato, with a significantly wide range extension from northern Japan, and southern Kuril Islands to the South China Sea. We also provide comparisons of the morphological measurements, first description of sagittae otoliths, and a partial sequence of the cytochrome oxidase subunit I gene for the specimen studied in this study.

Co-products from the frozen fish processing industry often lead to financial losses. Therefore, it is essential to transform these co-products into profitable goods. This study explores the production of fish protein hydrolysates (FPH) from three co-products: the heads and bones of black scabbardfish (Aphanopus carbo), the carcasses of gilthead seabream (Sparus aurata), and the trimmings of Nile perch (Lates niloticus). Four enzymatic hydrolysis systems were tested: an endopeptidase (Alcalase, A), an exopeptidase (Protana, P), two-stage hydrolysis with an endopeptidase followed by an exopeptidase (A + P), and a single stage with endo- and exopeptidase (AP). The results show that combined enzymatic treatments, especially single-stage Alcalase and Protana (AP), achieved high protein yields (80%) and enhanced degrees of hydrolysis (34 to 49%), producing peptides with lower molecular weights. FPH exhibited significant antioxidant activity, in 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, with EC50 values below 5 mg/mL. Additionally, AP hydrolysates demonstrated over 60% angiotensin-converting enzyme (ACE) inhibition at 5 mg/mL, indicating potential antihypertensive applications. Antidiabetic and anti-Alzheimer activities were present, but at relatively low levels. AP hydrolysates, especially from gilthead seabream, proved to be the most promising. This study highlights the value of fish co-products as sources of functional peptides, contributing to waste reduction, and their potential applications in food, agriculture, and nutraceuticals.

Pelagic accumulations of fish are formed above the underwater mountains of the Whale Ridge in the evening and at night, but not observed during daylight hours. The study of such an accumulation above one of the mountains reveals its structure. The central part of the cluster consists of splendid alfonsino Beryx splendens, silver scabbardfish Lepidopus caudatus and oilfish Ruvettus pretiosus tend to keep on the periphery of the splendid alfonsino accumulation . Previously, it was found that food of splendid alfonsino, silver scabbardfish, rosefish Helicolenus mouchezi, Richardson’s boarfish Pentaceros richardsoni, and Cape bonnetmouth Emmelichthys nitidus consisted of organisms forming sound-scattering layers (SSL) above the underwater mountains. The composition of food and the daily dynamics of feeding of the listed commercial fish species indicate that they use two feeding tactics. In the first case, rosefish, Richardson’s boarfish, and Cape bonnetmouth forage for most of their food during the day at the bottom, when the SSL-forming organisms descend to the top of the underwater mountain during the diel migration. In the second case, splendid alfonsino, silver scabbardfish, and oilfish as part of a structured pelagic aggregation feed at night on the organisms rising into the upper layers of the water and forming sound-scattering layers. This tactic expands the possibilities for feeding fish that form pelagic aggregations in the dark hours of the day and allows the use of organisms both brought by the current to the mountain top and those that descended here earlier during the diel migration and then stayed until the beginning of the evening.

Summary Commercial fishery landings of the black scabbardfish, Aphanopus carbo, from the Madeira mid‐water drifting longline fleet (northeastern Atlantic) were studied for 2 years within a Portuguese government programme for fishing management. The process noted that 20% of the total catch corresponded to the intermediate scabbardfish, Aphanopus intermedius. Length‐frequency distribution, and age, growth and reproduction of both species were analysed and compared. The results revealed significant differences in age and growth in influencing the length‐frequency distributions. Intermediate scabbardfish attained the largest size (148 cm TL) and age (15 years). However, the two species had similar reproductive strategies. According to data published on A. carbo in this region, it is thought to be very likely that previous studies unintentionally mixed both species together in their analyses.

The vertebrate ancestor possessed ultraviolet (UV) vision and many species have retained it during evolution. Many other species switched to violet vision and, then again, some avian species switched back to UV vision. These UV and violet vision are mediated by short wavelength-sensitive (SWS1) pigments that absorb light maximally (λmax) at approximately 360 and 390-440 nm, respectively. It is not well understood why and how these functional changes have occurred. Here, we cloned the pigment of scabbardfish (Lepidopus fitchi) with a λmax of 423 nm, an example of violet-sensitive SWS1 pigment in fish. Mutagenesis experiments and quantum mechanical/molecular mechanical (QM/MM) computations show that the violet-sensitivity was achieved by the deletion of Phe-86 that converted the unprotonated Schiff base-linked 11-cis-retinal to a protonated form. The finding of a violet-sensitive SWS1 pigment in scabbardfish suggests that many other fish also have orthologous violet pigments. The isolation and comparison of such violet and UV pigments in fish living in different ecological habitats will open an unprecedented opportunity to elucidate not only the molecular basis of phenotypic adaptations, but also the genetics of UV and violet vision.

Among the five groups of visual pigments in vertebrates, the rhodopsin type 2 (RH2) group shows the largest number of gene duplication events. We have isolated three intact and one nonfunctional RH2 opsin genes each from Northern lampfish (Stenobrachius leucopsarus) and scabbardfish (Lepidopus fitchi). Using the deduced amino acid sequences of these and other representative RH2 opsin genes in vertebrates, we have estimated the divergence times and evolutionary rates of amino acid substitution at various stages of RH2 opsin evolution. The results show that the duplications of the lampfish and scabbardfish RH2 opsins have occurred ∼60 and ∼30 million years ago (Ma), respectively. The evolutionary rates of RH2 opsins in the early vertebrate ancestors were ∼0.25 × 10−9/site/year, which increased to ∼1 × 10−9 to 3 × 10−9/site/year in euteleost lineages and to ∼0.3 × 10−9 to 0.5 × 10−9/site/year in coelacanth and tetrapods.

The channel scabbardfish, Evoxymetopon taeniatus Gill, 1863 has not been known from the Philippine waters. Our presently reported finding of two specimens (114.5 and 133.1 cm SL) of this species from the Philippines extends the range of this species to the central Indo-Pacific. The specimens captured were both male, one with developing gonads, and the other one-mature. We examined and described the fish found, providing morphometric and meristic analyses. The species can be distinguished from its congeners by having a convex upper head profile, steep sagittal crest slope, 82 dorsal fin rays with a defined notched at the tenth ray, a black dorsal fin membrane before the notch, and 15 externally visible anal fin rays that are bound with a membrane. The analyses included also relations with size of the four known Evoxymetopon species. Only one significant relation was revealed by the regression analyses-between SL and % pre-anal length. We provided also an updated identification key for the genus.