Past and recent demographic histories of western Mediterranean demersal chondrichthyans

Chondrichthyans (sharks, rays and chimaeras) play a key role in marine ecosystems, since they are top predators. Because of their life-history traits (slow growth, late maturity and low fecundity), they are especially vulnerable to fishing. In the Mediterranean, which hosts 7% of living chondrichthyans, a notable change in marine ecosystems has occurred due to anthropogenic impacts, with overfishing as one of the most important. For this reason, and because these species can be an important by-catch of fisheries, the International Union for Conservation of Nature (IUCN) considers this region a key hotspot of extinction risk for chondrichthyans. This Thesis contributes to improve the scientific knowledge of chondrichthyans on the circalittoral and bathyal soft bottoms along the western Mediterranean. Methods traditionally used to study population dynamics and biological communities, jointly with molecular tools, were applied to assess the past and present status of these vulnerable species. Data and samples were obtained during the MEDITS bottom trawl research surveys, developed annually in spring-summer since 1994 throughout the four geographic sub-areas (GSAs) established by the General Fisheries Commission for the Mediterranean (GFCM) in the study area: Northern Alboran Sea (GSA01) and Alboran Island (GSA02) considered jointly as GSA01, Balearic Islands (GSA05) and Northern Spain (GSA06). A total of 33 species of demersal chondrichthyans, belonging to 13 families were identified, of which 26, 28, and 19 species were caught in GSA01, GSA05 and GSA06, respectively. Two different assemblages were detected in each GSA, corresponding to the continental shelf and slope. The highest values of diversity, abundance, and biomass were recorded on the continental shelf of GSA05 and the slope of GSA01, while GSA06 showed the lowest values at both depth strata. These results can be explained by differences in trawl fishing exploitation and types of bottom between GSAs. Biological parameters such as optimum depth, length at first maturity, and size structure are provided for the most abundant species: Scyliorhinus canicula, Galeus melastomus, Etmopterus spinax, and Raja clavata. Spatio-temporal trends show fairly stable populations over the last 20 years regarding richness, abundance and biomass, even with an increment in density of species dwelling on the continental shelf and the most abundant on the slope, but decreasing trends in some other deep water species. This can be related to the reduction of trawl fishing effort on the continental shelf over the last decades, because fishing fleet has been reduced and displaced towards deeper waters. Genetic analyses revealed contrasting population patterns in S. canicula and G. melastomus, the two most abundant chondrichthyans on the continental shelf and slope, respectively. The first species showed genetic differences and low connectivity between Alboran Sea (GSA01-GSA02) and Balearic Sea (GSA05-GSA06), while the second one did not show geographic differences. Distinct demographic histories were also detected for both species. While G. melastomus exhibited a recent population expansion, S. canicula showed stability at present, but signs of past bottleneck events. Phylogenetic results revealed a parallel evolutionary history between batoids and the Mediterranean, with two important speciation events: i) during the Eocene-Oligocene transition, when almost all genera were originated; and ii) during the Miocene, when almost all current species appeared. Depth and benthic habitats were shown as the main drivers of speciation in Raja genera, both being of equal importance alongside physical distance and geographical barriers. Molecular analysis showed the presence of 18 batoids in the western Mediterranean and revealed misidentifications based only on morphological characters, including the confirmation of Dasyatis cf. tortonesei as a valid species and the presence of Dipturus nidarosiensis in the MediterraneanHistorias demográficas pasadas y recientes de los condrictios demersales del Mediterráneo Occidental. Los condrictios (tiburones, rayas y quimeras) desempeñan un papel clave en los ecosistemas marinos, dado que son depredadores apicales. Debido a las características de su ciclo vital (crecimiento lento, madurez tardía y baja fecundidad), son especialmente vulnerables a la pesca. El Mediterráneo, que alberga alrededor del 7% de los condrictios actuales, ha sufrido cambios importantes en sus ecosistemas marinos, causados por los impactos antropogénicos, entre los cuales la sobrepesca es uno de los más importantes. Por esta razón, y debido a que estas especies son capturadas frecuentemente de forma accidental en las pesquerías, la Unión Internacional para la Conservación de la Naturaleza (UICN) considera esta región como un punto clave de riesgo de extinción para los condrictios. Esta Tesis contribuye a mejorar el conocimiento científico de los condrictios en los fondos circalitorales y batiales del Mediterráneo Occidental. Se han aplicado métodos tradicionales de estudio de dinámica de poblaciones y comunidades biológicas, así como herramientas moleculares, con el propósito de evaluar la situación pasada y presente de estas especies vulnerables. Los datos y muestras se obtuvieron durante las campañas de investigación MEDITS, con arte de arrastre de fondo, realizadas anualmente desde 1994 en primavera-verano, a lo largo de cuatro sub-áreas geográficas (GSAs), establecidas por la Comisión General de Pesca para el Mediterráneo (CGPM) en el área de estudio: Norte del Mar de Alborán (GSA01) e Isla de Alborán (GSA02), considerados conjuntamente como GSA01, Islas Baleares (GSA05) y Norte de España (GSA06). Se han identificado un total de 33 especies de condrictios demersales, pertenecientes a 13 familias, de los cuales 26, 28 y 19 especies fueron capturados en la GSA01, GSA05 y GSA06, respectivamente. Se han detectado dos comunidades diferentes en cada GSA, que corresponden a la plataforma continental y al talud. Los valores más altos de diversidad, abundancia y biomasa se han obtenido en la plataforma continental de la GSA05 y en el talud de la GSA01, mientras que la GSA06 ha mostrado los valores más bajos en ambos estratos batimétricos. Estos resultados se pueden explicar por las diferencias en el esfuerzo de la pesca de arrastre y los tipos de fondo entre estas GSAs. Se han estimado parámetros biológicos (profundidad optima, talla de primera madurez y frecuencia de tallas) de las especies más abundantes: Scyliorhinus canicula, Galeus melastomus, Etmopterus spinax y Raja clavata. Las tendencias espacio-temporales muestran poblaciones bastante estables durante los últimos 20 años con respecto a la riqueza de especies, abundancia y biomasa, incluso con un aumento de la densidad de especies que habitan la plataforma continental y en la especie más abundante en el talud, pero con tendencias decrecientes en algunas otras especies de gran profundidad. Esto se puede relacionar con la reducción del esfuerzo de la pesca de arrastre en la plataforma continental durante las últimas décadas, a causa de la disminución de la flota y de su desplazamiento hacia aguas más profundas. Los análisis genéticos han mostrado que S. canicula y G. melastomus, las dos especies de condrictios más abundantes de la plataforma continental y el talud, respectivamente, tienen patrones poblacionales distintos. La primera ha presentado diferencias genéticas y baja conectividad entre el Mar de Alborán (GSA01-GSA02) y el Mar Balear (GSA05-GSA06), pero la segunda especie no ha mostrado estas diferencias geográficas. También se ha detectado una historia demográfica distinta entre ambas especies. Mientras que G. melastomus ha tenido una expansión poblacional reciente, S. canicula muestra mayor estabilidad, pero con evidencias de haber sufrido eventos de cuello de botella en el pasado. Los resultados filogenéticos han mostrado una historia evolutiva paralela de los batoideos y el Mediterráneo, con dos importantes eventos de especiación: i) durante la transición Eoceno-Oligoceno, cuando se originaron casi todos los géneros; y ii) durante el Mioceno, cuando aparecieron casi todas las especies actuales. Se ha demostrado que la profundidad y los hábitats bentónicos son los principales factores de especiación en el género Raja, siendo de igual importancia que las barreras geográficas y la distancia física. El análisis molecular ha demostrado la presencia de 18 especies de batoideos en el Mediterráneo Occidental y ha evidenciado identificaciones erróneas basadas sólo en caracteres morfológicos. Se ha confirmado Dasyatis cf. tortonesei como especie válida y la presencia de Dipturus nidarosiensis en el MediterráneoHistòries demogràfiques passades i recents dels condrictis demersals de la Mediterrània Occidental. Els condrictis (taurons, rajades i quimeres) tenen un paper clau en els ecosistemes marins, ja que són depredadors apicals. Per les característiques del seu cicle vital (creixement lent, maduresa tardana i baixa fecunditat), són especialment vulnerables a la pesca. La Mediterrània, on hi ha al voltant del 7% dels condrictis actuals, ha sofert canvis importants en els seus ecosistemes marins, causats pels impactes antropogènics, entre els quals la sobrepesca és un dels més importants. Per aquesta raó, i pel fet que aquestes espècies són capturades freqüentment de forma accidental a les pesqueries, la Unió Internacional per a la Conservació de la Naturalesa (IUCN) considera aquesta regió com un punt clau de risc d'extinció per als condrictis. Aquesta Tesi contribueix a millorar el coneixement científic dels condrictis en els fons circalitorals i batials de la Mediterrània Occidental. S'han aplicat mètodes d'estudi tradicionals de dinàmica de poblacions i comunitats biològiques, així com eines moleculars amb el propòsit d'avaluar la situació passada i present d'aquestes espècies vulnerables. Les dades i mostres s’han obtingut durant les campanyes d'investigació MEDITS, amb art de ròssec de fons, realitzades anualment des del 1994 a la primavera-estiu, al llarg de quatre subàrees geogràfiques (GSAs) establertes per la Comissió General de Pesca per a la Mediterrània (CGPM) en l'àrea d'estudi: Nord de la Mar d'Alborán (GSA01) i Illa d'Alborán (GSA02), considerats conjuntament com GSA01, Illes Balears (GSA05) i Nord d'Espanya (GSA06). S'han identificat un total de 33 espècies de condrictis demersals, que pertanyen a 13 famílies, de les quals 26, 28 i 19 espècies van ser capturades a les GSA01, GSA05 i GSA06, respectivament. A cada GSA s'han detectat dues comunitats diferents, que corresponen a la plataforma continental i al talús. Els valors més alts de diversitat, abundància i biomassa s'han obtingut en la plataforma continental de la GSA05 i en el talús de la GSA01, mentre que la GSA06 ha mostrat els valors més baixos en ambdós estrats batimètrics. Aquests resultats es poden explicar per les diferències en l'esforç de la pesca de ròssec i els tipus de fons entre aquestes GSAs. S'han estimat paràmetres biològics (profunditat òptima, talla de primera maduresa i freqüència de talles) de les espècies més abundants: Scyliorhinus canicula, Galeus melastomus, Etmopterus spinax i Raja clavata. Les tendències espai-temporals mostren poblacions bastant estables durant els últims 20 anys pel que fa a la riquesa d'espècies, abundància i biomassa, fins i tot amb un augment de la densitat d'espècies que habiten la plataforma continental i l'espècie més abundant al talús, però amb tendències decreixents en algunes altres espècies de gran profunditat. Això es pot relacionar amb la reducció de l'esforç de la pesca de ròssec en la plataforma continental durant les últimes dècades, a causa de la disminució de la flota i del seu desplaçament cap a aigües més profundes. Les anàlisis genètiques han mostrat que S. canicula i G. melastomus, les dues espècies de condrictis més abundants en la plataforma continental i el talús, respectivament, tenen patrons poblacionals diferents. La primera ha presentat diferències genètiques i baixa connectivitat entre la Mar d'Alborán (GSA01-GSA02) i la Mar Balear (GSA05-GSA06), però la segona espècie no ha mostrat aquestes diferències geogràfiques. També s'ha detectat una història demogràfica diferent entre ambdues espècies. Mentre que G. melastomus ha tingut una expansió poblacional recent, S. canicula mostra major estabilitat, però amb evidències d'haver sofert esdeveniments de coll de botella en el passat. Els resultats filogenètics han mostrat una història evolutiva paral•lela dels batoïdeus i la Mediterrània, amb dos importants esdeveniments d'especiació: i) durant la transició Eocè-Oligocè, quan es van originar gairebé tots els gèneres; i ii) durant el Miocè, quan van aparèixer la majoria de les espècies actuals. S'ha demostrat que la profunditat i els hàbitats bentònics són els principals factors d'especiació en el gènere Raja, sent d'igual importància que les barreres geogràfiques i la distància física. L'anàlisi molecular ha demostrat la presència de 18 espècies de batoïdeus a la Mediterrània Occidental i ha evidenciat identificacions errònies basades només en caràcters morfològics. S’ha confirmat Dasyatis cf. tortonesei com a espècie vàlida i la presència de Dipturus nidarosiensis a la Mediterràni

First substantiated record of Raja asterias Delaroche, 1809 (Elasmobranchii: Rajiformes: Rajidae) in the Gulf of Cádiz, North-eastern Atlantic

The Mediterranean starry ray, Raja asterias, considered endemic in the Mediterranean, has recently been reported by other authors from Atlantic fisheries in southern Portugal and northern Morocco. There has been, however, no substantiated record of the species outside the Mediterranean. This fact and the easiness of confusion of R. asterias with other species have probably prevented those records from being taken into account in the recent catalogue of North Atlantic elasmobranchs species, in the assessment of the population status of this species, and in recent annotated global checklists of chondrichthyans. In our study, a specimen of R. asterias was collected from the Gulf of Cádiz and its species identity was assessed based on morphological and molecular methods. The presently reported finding constitutes a substantiated record of R. asterias from the Atlantic. Based on this record, previously reported catches of the Mediterranean starry ray in the Atlantic should be confirmed, and if so, these populations should be included in future assessments of this vulnerable species and in the description of its geographic distributionVersión del editor0,54

Biological parameters, ecology and population trends of the Mediterranean endemic skate, Raja polystigma, in the Balearic Islands

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).En prensa1,00

Declining Population Sizes and Loss of Genetic Diversity in Commercial Fishes: A Simple Method for a First Diagnostic

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.En prens

New morphological and molecular evidence confirm the presence of the Norwegian skate Dipturus nidarosiensis (Storm, 1881) in the Mediterranean Sea and extend its distribution to the western basin

The present study confirms the presence of the Norwegian skate Dipturus nidarosiensis (Storm, 1881) in the Mediterranean Sea, by means of morphological traits and molecular markers providing the first record of this species in the Alboran Sea. Cannas et al. (2010) reported D. nidarosiensis for the first time in the Mediterranean from specimens captured in the central western basin, but Ebert & Stehmann (2013) and Stehmann et al. (2015) considered these records "likely refer to the smaller morphotype, Dipturus sp.", a species not yet described. Eight specimens of the Dipturus genus (Rajiformes: Rajidae) were caught off the Alboran Island (western Mediterranean) in 2012, 2013 and 2016, between 620 and 819 m depth. These specimens showed morphometric diagnostic features corresponding to those of Norwegian skates from the Northeast Atlantic and the central western Mediterranean Sea. Moreover, the Alboran individuals were genetically compared to Northeast Atlantic specimens available in GenBank by means of two mitochondrial DNA fragments: cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb). Analyses showed that the Northeast Atlantic Norwegian skate specimens and the Alboran Sea ones were genetically similar and shared haplotypes, corroborating the identification of the Alboran individuals as Dipturus nidarosiensis. However, they were different from other Dipturus species distributed throughout the Northeast Atlantic and the Mediterranean Sea. Our results confirm the occurrence of this deep-sea large skate species in the Mediterranean, although the IUCN Red List of Threatened Species does not consider it possible (Stehmann et al., 2015)Versión del edito

Potential factors influencing the condition of demersal sharks in the Mediterranean deep sea ecosystems

The Alboran Sea and the Balearic Islands are two contrasting areas in terms of primary productivity. The former is among the most productive areas of the whole Mediterranean Sea, whereas the Balearic Islands is among the less productive ones in the western Mediterranean. The two areas also show different patterns in the bottom trawl fishing footprint. In the Alboran Sea, the fishing effort on the upper slope is much higher than in Balearic Islands. However, the opposite applies to the middle slope, the vast majority of it remaining unexploited in Alboran Sea, whereas a widespread fishery targeting blue and red shrimp Aristeus antennatus develops in Balearic Islands. Galeus melastomus is a small demersal shark species inhabiting slope bottoms, where adults and juveniles are segregated and concentrate in the middle and upper slope, respectively. It feeds intensively on mesopelagic preys which, in turn, feed on low trophic level organisms close to primary producers. In this work we aimed to study the effect of surface primary production on the condition of deep sea demersal communities. We compared the condition, diet and potential intra- and inter-species competition for feeding resources in the juveniles of G. melastomus between Alboran Sea and Balearic Islands. The comparisons of Le Cren’s relative condition factor, and hepatosomatic and digestivosomatic indices evidenced an opposite pattern to that a priori expectable: better condition in the less productive area. The analysis of stomach contents showed similar diets in both areas, but lower food ingestion in Alboran Sea than in Balearic Islands. Different abundances of potential intra- and inter-specific competitors for feeding resources in the two areas, apparently linked to the different fishing footprints, seems the most likely explanation for the better nourished individuals in Balearic Islands. Whereas juveniles of G. melastomus dominate the shark community in the Balearic Islands upper slope, where the presence of adults of this species is almost negligible, in Alboran Sea this stratum is dominated by adults and potential competitors of other small demersal shark species. All shark species together, including G. melastomus, showed abundances 38% higher in Alboran than in Balearic Islands. Our results show that condition of deep sea demersal fish is ruled by complex inter-relationships among different factors, needing the combination of biological, ecological and fisheries knowledge to understand its variability.En prensa2,42

Recovery Signals of Rhodoliths Beds since Bottom Trawling Ban in the SCI Menorca Channel (Western Mediterranean)

One of the objectives of the LIFE IP INTEMARES project is to assess the impact of bottom trawling on the vulnerable benthic habitats of the circalittoral bottoms of the Menorca Channel (western Mediterranean), designated a Site of Community Importance (SCI) within the Natura 2000 network. The present study compares the epibenthic communities of four areas, subjected to different bottom trawl fishing intensity levels. The assignment of fishing effort levels was based on the fishing effort distribution in the area calculated from Vessel Monitoring System (VMS) data and the existence of two Fishing Protected Zones in the Menorca Channel. Biological samples were collected from 39 beam trawl stations, sampled during a scientific survey on April 2019. We compare the diversity, composition, and density of the epibenthic flora and fauna, together with the rhodoliths coverage and the morphology of the main species of rhodoliths of four areas subjected to different levels of bottom trawl fishing effort, including one that has never been impacted by trawling. Our results have shown negative impacts of bottom trawling on rhodoliths beds and the first signals of their recovery in areas recently closed to this fishery, which indicate that this is an effective measure for the conservation of this habitat of special interest and must be included in the management plan required to declare the Menorca Channel as a Special Area of Conservation.En prens

Call me by my name: unravelling the taxonomy of the gulper shark genus Centrophorus in the Mediterranean Sea through an integrated taxonomic approach

The current shift of fishery efforts towards the deep sea is raising concern about the vulnerability of deep-water sharks, which are often poorly studied and characterized by problematic taxonomy. For instance, in the Mediterranean Sea the taxonomy of genus Centrophorus has not been clearly unravelled yet. Since proper identification of the species is fundamental for their correct assessment and management, this study aims at clarifying the taxonomy of this genus in the Mediterranean Basin through an integrated taxonomic approach. We analysed a total of 281 gulper sharks (Centrophorus spp.) collected from various Mediterranean, Atlantic and Indian Ocean waters. Molecular data obtained from cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S), NADH dehydrogenase subunit 2 (ND2) and a portion of a nuclear 28S ribosomal DNA gene region (28S) have highlighted the presence of a unique mitochondrial clade in the Mediterranean Sea. The morphometric results confirmed these findings, supporting the presence of a unique and distinct morphological group comprising all Mediterranean individuals. The data strongly indicate the occurrence of a single Centrophorus species in the Mediterranean, ascribable to C. cf. uyato, and suggest the need for a revision of the systematics of the genus in the area.En prens

Improving Scientific Knowledge of Mallorca Channel Seamounts (Western Mediterranean) within the Framework of Natura 2000 Network

The scientific exploration of Mallorca Channel seamounts (western Mediterranean) is improving the knowledge of the Ses Olives (SO), Ausias March (AM), and Emile Baudot (EB) seamounts for their inclusion in the Natura 2000 network. The aims are to map and characterize benthic species and habitats by means of a geological and biological multidisciplinary approach: high-resolution acoustics, sediment and rock dredges, beam trawl, bottom trawl, and underwater imagery. Among the seamounts, 15 different morphological features were differentiated, highlighting the presence of 4000 pockmarks, which are seafloor rounded depressions indicators of focused fluid flow escapes, usually gas and/or water, from beneath the seabed sediments. So far, a total of 547 species or taxa have been inventoried, with sponges, fishes, mollusks, and crustaceans the most diverse groups including new taxa and new geographical records. Up to 29 categories of benthic habitats have been found, highlighting those included in the Habitats Directive: maërl beds on the summits of AM and EB, pockmarks around the seamounts and coral reefs in their rocky escarpments as well as fields of Isidella elongata on sedimentary bathyal bottoms. Trawling is the main demersal fishery developed around SO and AM, which are targeted to deep water crustaceans: Parapenaeus longirostris, Nephrops norvegicus, and Aristeus antennatus. This study provides scientific information for the proposal of the Mallorca Channel seamounts as a Site of Community Importance and for its final declaration as a Special Area of Conservation

Influence of elevated-CRP level-related polymorphisms in non-rheumatic Caucasians on the risk of subclinical atherosclerosis and cardiovascular disease in rheumatoid arthritis

Association between elevated C-reactive protein (CRP) serum levels and subclinical atherosclerosis and cardiovascular (CV) events was described in rheumatoid arthritis (RA). CRP, HNF1A, LEPR, GCKR, NLRP3, IL1F10, PPP1R3B, ASCL1, HNF4A and SALL1 exert an influence on elevated CRP serum levels in non-rheumatic Caucasians. Consequently, we evaluated the potential role of these genes in the development of CV events and subclinical atherosclerosis in RA patients. Three tag CRP polymorphisms and HNF1A, LEPR, GCKR, NLRP3, IL1F10, PPP1R3B, ASCL1, HNF4A and SALL1 were genotyped in 2,313 Spanish patients by TaqMan. Subclinical atherosclerosis was determined in 1,298 of them by carotid ultrasonography (by assessment of carotid intima-media thickness-cIMT-and presence/absence of carotid plaques). CRP serum levels at diagnosis and at the time of carotid ultrasonography were measured in 1,662 and 1,193 patients, respectively, by immunoturbidimetry. Interestingly, a relationship between CRP and CRP serum levels at diagnosis and at the time of the carotid ultrasonography was disclosed. However, no statistically significant differences were found when CRP, HNF1A, LEPR, GCKR, NLRP3, IL1F10, PPP1R3B, ASCL1, HNF4A and SALL1 were evaluated according to the presence/absence of CV events, carotid plaques and cIMT after adjustment. Our results do not confirm an association between these genes and CV disease in RA