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The sponge fauna of the Western Mediterranean stands as one of the most studied in the world. Yet sampling new habitats and a poorly studied region like the Balearic Islands highlights once again our limited knowledge of this group of animals. This work focused on demosponges of the order Tetractinellida collected in several research surveys (2016–2021) on a variety of ecosystems of the Balearic Islands, including shallow caves, seamounts and trawl fishing grounds, in a broad depth range (0–725 m). Tetractinellid material from the North Atlantic and more than twenty type specimens were also examined and, for some, re-described in this work. All species were barcoded with the traditional molecular markers COI (Folmer fragment) and 28S (C1-C2 or C1-D2 fragment). A total of 36 species were identified, mostly belonging to the family Geodiidae (15 species), thereby bringing the number of tetractinellids recorded in the Balearic Islands from 15 to 39. Eight species from this study are new: Stelletta mortarium sp. nov., Penares cavernensis sp. nov., Penares isabellae sp. nov., Geodia bibilonae sp. nov., Geodia microsphaera sp. nov. and Geodia matrix sp. nov. from the Balearic Islands; Geodia phlegraeioides sp. nov. and Caminus xavierae sp. nov. from the North East Atlantic. Stelletta dichoclada and Erylus corsicus are reported for the first time since their description in Corsica in 1983. Pachastrella ovisternata is documented for the first time in the Mediterranean Sea. Finally, after comparisons of type material, we propose new synonymies: Geodia anceps as a junior synonym of Geodia geodina, Erylus cantabricus as a junior synonym of Erylus discophorus and Spongosorites maximus as a junior synonym of Characella pachastrelloides.

The Balearic Archipelago (western Mediterranean) is an area of great ecological interest due to the combination of complex geomorphology, highly oligotrophic waters and low fishing pressure. Sponges play a key role in benthic habitats, providing structural complexity and significantly contributing to their diversity and biomass. Here, we present an insight into the sponge communities of this archipelago from the analysis of samples collected during several scientific research surveys carried out on bottom trawl fishing grounds around the Balearic Islands and on sedimentary and rocky bottoms of the Mallorca Channel seamounts. Sampling was carried out with experimental bottom trawl, beam trawl, rock dredge and remotely operated vehicle (ROV). We analyzed species presence/absence data using multivariate methods in order to identify assemblages. Once identified, we characterized their biodiversity, biomass and taxonomic composition. A dbRDA analysis was conducted to test the influence of environmental variables and fishing pressure on the sponge communities. Up to 350 species are reported: 220 at bottom trawl fishing grounds and 189 at seamounts. Communities were structured by depth, temperature, currents, substrate and fishing pressure with sponge presence/absense, biomass and diversity also linked to the presence of deep algae beds. Taxonomic composition differed between bottom trawl fishing grounds and the seamounts, where this fishing activity is almost negligible, pointing to different sensitivity to this fishing impact among the different orders, particularly for Tetractinellida, which was much more diverse and abundant at seamounts.

Fisheries management requires the best scientific knowledge on the exploitation and conservation status of stocks. This is challenging for by-catch species, for which necessary data for their assessment is more limited than for target ones. That is the case for the thornback ray, Raja clavata, in the Balearic Islands (western Mediterranean), whose exploitation and conservation status are addressed here for the first time, in an integrative approach, by using innovative assessment methods and genetic diversity analysis. The time series of fishing landings from 1964 and MEDITS trawl survey data from 2004 were used to apply CMSY++ and Bayesian state-space Schaefer production models. We also estimated the genetic diversity of the Cytochrome C Oxidase subunit I mitochondrial gene from 31 individuals collected during MEDITS surveys. The species showed overexploitation with a current fishing mortality (F) below that producing maximum sustainable yield (FMSY), but with a current stock biomass (B) lower than BMSY. Despite the fact that the exploitation status is stable or even has improved in the last decades, the overexploitation period since the late 1970s seems to have reduced levels of genetic diversity, below those of related species and other populations of R. clavata. This low genetic diversity may entail the loss of adaptive potential, making the species more vulnerable to fishing and the current climate change.

Within the context of the ecosystem approach to fisheries management, an ecosystem model was developed for the Balearic Islands in the early 2000s, covering from 0 to 800 m of depth. The aim of the study was to describe the structure and functioning of the ecosystem together with the fishing impacts. The results show that the biomass of the primary producers (PP), mainly dominated by Posidonia oceanica meadows and red algae beds, represented a high percentage of the biomass (39.20%) in the ecosystem. Most of the trophic flows occurred between PP (mostly benthic) and trophic level II. The mixed trophic impact analysis also highlighted a positive impact of the functional groups (FGs) at the base of the food web. Besides, there were important trophic flows between several demersal FGs, and many groups of the pelagic compartment, confirming the importance of the benthopelagic coupling previously reported. The mean trophic level of the catch (mTLc=2.76) was lower than those reported in adjacent areas due to the discard of benthic producers. By excluding benthic PP, the Balearic Islands showed the highest mTLc (3.44) among all the Mediterranean areas modelled, probably due to differences in the trophic structure, lower fisheries exploitation levels and lower development of the purse seine fleet targeting small pelagic fishes. The mean transfer efficiency (21.80%) was double than the global average (10%), which highlights the oligotrophy of the system, the importance of demersal production which has lower rates of transfer through the food web, and a more efficient use of nutrients in the ecosystem. Sponges, one of the most important groups of benthic invertebrates in the Balearic Archipelago, are known to recycle dissolved organic matter, which is reintroduced into the food web similar to the microbial loop, but the magnitude of this and other processes remains still unknown in this area. The present study is a first step to develop spatio-temporal simulations under diffe

Available information and potential data gaps for non-fish marine organisms (cnidarians, crustaceans, echinoderms, molluscs, sponges, mammals, reptiles, and seabirds) covered by the global database SeaLifeBase were reviewed for eight marine ecosystems (Adriatic Sea, Aegean Sea, Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea, western Mediterranean Sea, Levantine Sea) across European Seas. The review of the SeaLifeBase dataset, which is based on published literature, analyzed information coverage for eight biological characteristics (diet, fecundity, maturity, length-weight relationships, spawning, growth, lifespan, and natural mortality). These characteristics are required for the development of ecosystem and ecological models to evaluate the status of marine resources and related fisheries. Our analyses revealed that information regarding these biological characteristics in the literature was far from complete across all studied areas. The level of available information was nonetheless reasonably good for sea turtles and moderate for marine mammals in some areas (Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea and western Mediterranean Sea). Further, seven of the areas have well-studied species in terms of information coverage for biological characteristics of some commercial species whereas threatened species are generally not well studied. Across areas, the most well-studied species are the cephalopod common cuttlefish (Sepia officinalis) and the crustacean Norway lobster (Nephrops norvegicus). Overall, the information gap is narrowest for length-weight relationships followed by growth and maturity, and widest for fecundity and natural mortality. Based on these insights, we provide recommendations to prioritize species with insufficient or missing biological data that are common across the studied marine ecosystems and to address data deficiencies.

[EN] Blache’s flounder, Arnoglossus blachei Stauch, 1965, is redescribed from the eastern Atlantic (Morocco south to Namibia, including the Canary Islands, larvae reaching South Africa) and distinguished from the imperial flounder A. imperialis (Rafinesque, 1810) by having a live colouration of the lower side of males which is bright red (whitish in A. imperialis), the caudal fin with lateral-line scales 52-57 (vs. 58-63), and the dorsal-fin filaments in male light grey, with black margins, distally yellowish (vs. plain white). A lectotype is selected for Arnoglossus blachei. The species is compared with similar species. The externally similar species Arnoglossus imperialis is also redescribed; its distibution range is restricted to the Mediterranean and northeastern Atlantic, including Madeira and the Azores. Neotypes are selected to stabilize the usage of the names Bothus imperialis Rafinesque, 1810, Bothus punctatus Rafinesque, 1814, Rhombus cristatus Lowe, 1839 and Charybdia rhomdoidichthys Facciolà, 1885. Molecular analyses based on two mitochondrial fragments (12s rRNA and COI) clearly support the validity of A. blachei. Moreover, though A. blachei is morphologically close to A. imperialis, the two species show the highest genetic distances among all Arnoglossus species compared (including A. capensis, A. imperialis, A. laterna, A. rueppelii and A. thori). A key to the eastern Atlantic and Mediterranean species of Arnoglossus is presented., [ES] Se vuelve a describir el pez plano de Blache’s Arnoglossus blachei Stauch, 1965 del Atlántico oriental (desde el sur de Marruecos a Namibia incluido las Islas Canarias, pudiendo sus larvas llegar a Sudáfrica), y se distingue del pez plano imperial A. imperialis (Rafinesque, 1810) por tener, en fresco, una coloración rojo brillante en la parte inferior de los machos (blanquecina en A. imperialis), la aleta caudal con escamas en la línea lateral 52-57 (vs. 58-63), y en los machos, los filamentos de la aleta dorsal son de color gris claro, con márgenes negros y en su parte distal amarillenta (vs. blanco liso). La especie se compara con especies similares. Asimismo, la especie externamente similar Arnoglossus imperialis, se vuelve a describir, cuya área de distribución está restringida al Mediterráneo y Atlántico nororiental, incluidas Madeira y Azores. Además, se seleccionan neotipos para estabilizar el uso de los nombres Bothus imperialis Rafinesque, 1810, Bothus punctatus Rafinesque, 1814, Rhombus cristatus Lowe, 1839 y Charybdia rhomdoidichthys Facciolà, 1885. Los análisis moleculares basados en dos fragmentos mitocondriales (12s rRNA y COI) respaldan claramente la validez de A. blachei. Por otra parte, a pesar de que A. blachei es morfológicamente más cercano a A. imperialis, ambas especies muestran las distancias genéticas más largas entre todas las especies de Arnoglossus comparadas (A. capensis, A. imperialis, A. laterna, A. rueppelii y A. thori). Se presenta una clave para las especies de Arnoglossus del Atlántico oriental y Mediterráneo.

Gymnesigobius medits is reported for the first time after a recent description recorded from the Balearic Islands and from the slope of the Gulf of Vera on the Iberian Peninsula coast. The record from the Emile Baudot seamount on the Balearic Islands represents the deepest positive benthic gobiiform species record in general. The presence of the membrane connection between the pelvic fins in Gymnesigobius medits, presumed on the damaged fin in the original description, was confirmed. The recently described Gobius xoriguer is the first record from the Pitiusas and Columbretes islands and from the Iberian Peninsula coast. It appears to be widely distributed in the circalittoral bottoms, preferentially in red algae beds. Morphological identification of both species was confirmed using molecular analyses based on the sequencing of the mitochondrial cytochrome c oxidase subunit I (DNA barcode) gene. The deepest records of gobiiform fishes in oceans and seas are reviewed. The European seas, a well-studied area with eight gobiid species recorded deeper than 200 m, show high bathyal gobiid species richness compared to other areas. The real worldwide diversity of bathyal gobies, although only a fraction of the shallow water species richness of this taxon, is probably much larger than presently known.

More than half of the Mediterranean sharks and rays are threatened by fishing exploitation. However, population assessments are limited by the scarcity of specific data on fishing catches. In this study, we assessed temporal trends of the indicators developed within the European Marine Strategy Framework Directive over the last two decades in order to assess the conservation status of demersal sharks and batoids in the Balearic Islands, which represent an important fraction of the bycatch of bottom trawling in this area. On the basis of a georeferenced, fishery-independent dataset of 19 species of elasmobranchs, we analyzed 20 year time series (2002–2021) of nine indicators regarding area distribution, population size, population status, and community structure. Between 30% and 50% of the elasmobranch species and functional groups showed increasing trends in distribution area and population size. This was especially true for batoids, whereas the distribution area and population size of most sharks remained stable over the study period. The remaining indicators showed stability or, in some cases, variable trends. Only in one case did we find a negative trend sustained all along the time series (i.e., the proportion of R. radula large individuals in relation to the reference period). Overall, our results suggest that the populations of elasmobranchs from the Balearic Islands show stable or recovery trends, mainly in terms of distribution area and density. However, it remains elusive whether this community can recover to the levels of more than half a century ago, before the development of the bottom trawl fishery, or whether this apparent current steady state should be interpreted as a new equilibrium.

Available information and potential data gaps for non-fish marine organisms (cnidarians, crustaceans, echinoderms, molluscs, sponges, mammals, reptiles, and seabirds) covered by the global database SeaLifeBase were reviewed for eight marine ecosystems (Adriatic Sea, Aegean Sea, Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea, western Mediterranean Sea, Levantine Sea) across European Seas. The review of the SeaLifeBase dataset, which is based on published literature, analyzed information coverage for eight biological characteristics (diet, fecundity, maturity, length-weight relationships, spawning, growth, lifespan, and natural mortality). These characteristics are required for the development of ecosystem and ecological models to evaluate the status of marine resources and related fisheries. Our analyses revealed that information regarding these biological characteristics in the literature was far from complete across all studied areas. The level of available information was nonetheless reasonably good for sea turtles and moderate for marine mammals in some areas (Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea and western Mediterranean Sea). Further, seven of the areas have well-studied species in terms of information coverage for biological characteristics of some commercial species whereas threatened species are generally not well studied. Across areas, the most well-studied species are the cephalopod common cuttlefish (Sepia officinalis) and the crustacean Norway lobster (Nephrops norvegicus). Overall, the information gap is narrowest for length-weight relationships followed by growth and maturity, and widest for fecundity and natural mortality. Based on these insights, we provide recommendations to prioritize species with insufficient or missing biological data that are common across the studied marine ecosystems and to address data deficiencies.

Pinnotheres pisum (Linnaeus, 1767) is one of the pinnotherid crab species with the highest number of reported bivalve hosts. Here we first report this species living in the bivalve Glossus humanus (Linnaeus, 1758), and provide an update on P. pisum symbiotic associations (i.e., known hosts), reaching up to 34 taxa. Partial sequences of the mitochondrial gene cytochrome c oxidase subunit I were first obtained from P. pisum and the G. humanus host from the Mediterranean Sea, confirming conspecificity with specimens from the Atlantic Ocean of the same species.

Fisheries management requires the best scientific knowledge on the exploitation and conservation status of stocks. This is challenging for by-catch species, for which assessment data is more limited than for target ones. That is the case of chondrichthyan species, particularly vulnerable to fishing impacts due to their life history strategy. In the present study we use an integrative approach, including innovative assessment methods and genetic diversity analysis, to assess the exploitation and conservation status of six skate species in the Balearic Islands (western Mediterranean). Among them, Raja clavata is the most important species in terms of abundance and the unique with a time series of landings long enough (from 1964) to be used in production models. Thus, these data, along with information from bottom trawl surveys (since 2004) are used to apply CMSY++ and Bayesian state-space Schaefer production models to assess its exploitation status. For the rest of the species, the exploitation status is analysed with a novel production model, based on time series of abundance data from surveys (AMSY). The conservation status for all the analysed species is assessed by comparing the mitochondrial Cytochrome C Oxidase subunit I gene (COI) nucleotide diversity in the Balearic Islands populations against the COI genetic diversity benchmarks estimated for Elasmobranchii and Rajiformes species from sequences available in BOLDSystem. To do so, a small piece of pelvic fin from the specimens caught during the surveys was collected. The tissue is processed in the laboratory to extract DNA, amplify COI sequence through Polymerase Chain Reaction and for sequencing. Sequences are analysed to estimate nucleotide diversity of Balearic Islands populations of the studied species. Results show that exploitation and conservation status can present different patterns for the same species. That is the case of R. clavata, which showed that the stock is currently overexploited, even though

Exploited fish species may have or are experiencing declines in population sizes coupled with changes in their environmental conditions owing to global change. Declining populations might lead to a decrease in genetic diversity, which in turn may produce losses of adaptive potential to face current and future environmental changes. Thus, this study aims to answer a simple, even naive question, given the complexity of the subject: Could we use a simple method to obtain information on the loss of genetic diversity in exploited fish species? We investigated the use of the levels of genetic diversity in the widely used genetic marker Cytochrome C Oxidase subunit I (COI) mitochondrial gene. Estimates of genetic diversity in COI were obtained for populations of seven fish species with different commercial importance from the East China Sea. These estimates were contrasted against large datasets of genetic diversity in COI for fish species (East-Asian N=118, and worldwide N=1425), and six control species with known biology and history. We found that estimates of genetic diversity in COI match the expectations from theoretical predictions and known declines by fishing pressures. Thus, the answer to our question is affirmative and we conclude that estimates of genetic diversity in COI provide an effective first diagnostic of the conservation status of exploited fish species.

Elasmobranchs are a vulnerable group that has been overexploited for almost half a century in the Mediterranean. However, few elasmobranch species have been assessed because information on their basic biological parameters is lacking for most species. Raja polystigma is a poorly studied endemic skate in the Mediterranean. The aim of this work is to determine some basic life history parameters of this skate in the Balearic Islands. Data were collected from commercial catches and during MEDITS surveys. Total length varied from 17 to 59 cm for both sexes, with a higher proportion of females than males. Allometric and morphometric relationships differed between sexes, females being heavier for a given size. Females matured at a larger size than males (L50 47.7 cm and 38.4 cm, respectively). Potential fecundity ranged between 11 and 45 yolked oocytes per female, and spawning was observed mainly during winter and spring. Persistent hotspots of adults and juveniles were detected on the shallow shelf off the northwest of Mallorca and east of Menorca, with adults being found mainly in the shallow and juveniles in deeper areas. Time series of abundance and frequency of appearance showed stable trends throughout the study period (2003-2018).

Seamounts are globally important and essential ecosystems for supporting and maintaining marine biodiversity. In the Mallorca Channel, three prominent seamounts are present: Ausias March, Ses Olives and Emile Baudot. Currently, this area is being evaluated for inclusion in the Natura 2000 network. For this objective three surveys were conducted in the seamounts of the Mallorca Channel during July 2018 and July 2020. Samples of macro-invertebrates obtained in the deep sea revealed a rich fauna of Mollusca (68 species belonging to 40 families). New Mollusca occurrences included: four species of Gastropoda: Colus jeffreysianus, Cantrainea peloritana, Fusiturris similis, Gymnobela abyssorum, and seven species of Bivalvia: Pododesmus squama, Allogramma formosa, Asperarca nodulosa, Cetomya neaeroides, Spondylus gussonii, Haliris granulata and Policordia gemma. Where possible, the identification of these species was confirmed using the DNA barcoding method (sequencing of the cytochrome c oxidase subunit I). This study contributes towards filling the gap in knowledge of deep-sea mollusc fauna of the north-western Mediterranean

A new species of dragonet, Synchiropus f lavistrigatus sp. n. from the eastern tropical Atlantic, is described on the basis of 15 specimens. The new species is characterised within the subgenus Yerutius Whitley, 1931 by having 8 rays in the second dorsal fin (the last divided at its base), 8 anal-fin rays (the last divided at its base), 20–21 pec-toral-fin rays, a single upper unbranched pectoral-fin ray, 1–2 curved dorsal points on the upper margin of the pre-opercular spine (additional to the main tip), length of first spine of first dorsal fin in male 12.8–15.9% of standard length, in female 14.5–15.4%; caudal-fin length in male 27.7–32.2% of standard length, in female 25.5–27.9%; length of last ray of second dorsal fin in male 18.2–21.6% of standard length; length of last ray of anal fin in male 14.6–17.1% of standard length, in female 13.5–15.1%; second dorsal fin and caudal fin with oblique yellow bars in both sexes; anal fin with a distal dark streak in both sexes. We also provide molecular information, based on two mitochondrial fragments (COI and 12s rRNA), that clearly supports the morphological results confirming that S. f lavistrigatus sp. n. corresponds to a new species, distinct from S. phaeton (Günther, 1861). The new species is compared with other species of the subgenus.