Exploring diversity and distribution of demersal fish species from the Northern Alboran Sea and Gulf of Vera (Western Mediterranean Sea)

The Alboran Sea is a transition region between the Mediterranean basin and the Atlantic Ocean containing a mix of Mediterranean and Atlantic species. The Strait of Gibraltar, at the west end of the Alboran Sea, connects the Mediterranean with the Atlantic Ocean. The Gulf of Vera also occupies a strategic location in the Western Mediterranean, representing a transition zone between the Alboran Sea and the rest of the basins with a more distinctive Mediterranean character. The Alboran Sea is one of the most productive areas of the Mediterranean, in contrast to the Gulf of Vera that displays a more oligotrophic character. Despite of the interest of the study area the information about the distribution of demersal fishes is scarce. In the present study, the main aim is to analyse diversity and distribution of demersal fish species of circalittoral and bathyal soft bottoms of the Alboran Sea (with a higher Atlantic influence and primary production) and the Gulf of Vera (with a higher Mediterranean influence and lower primary production). Sampling was carried out in the scientific trawl survey MEDITS (International bottom trawl survey in the Mediterranean) between 30 and 800 m depth. All samples were taken from Estepona and Cabo de Palos between 1994-2015 in the Alboran Sea and between 1995-2008 and 2014-2015 in the Gulf of Vera. (Figure 1). A total of 818 samples (687 from Alboran and 131 from Vera) were considered for this study. For each haul, the abundance and weight of individuals per fish species were standardised to 1 hour towing in order to calculate both species abundance (number of individuals per 1 hour towing) (ind•h−1) and biomass (g•h−1). In order to identify fish assemblages, ordination and classification multivariate methods using fish species abundance and biomass per haul matrices were applied. Prior to analyses, all data were logarithmically transformed using log(x + 1) to minimise the weighting of extreme abundance or biomass values of certain species. An analysis of similarities (ANOSIM) was carried out for statistical comparisons of groups of samples according to the different factors considered (depth, Alboran vs. Vera). Species rarefaction curves were used to compare the species richness values of each fish assemblage. In addition, for each group, Shannon-Wiener (H’) and Taxonomic distinctness (Δ*) diversity indices were calculated. For comparisons of the mean values of the considered variables (abundance, biomass and diversity indices) across the identified assemblages and years, we used a non-parametric Kruskal–Wallis test. A total of 231 fish species have been identified considering all samples, with 215 spp. collected from Alboran (3 classes, 25 orders and 75 families) and 160 spp.. from Vera (2 classes, 21 orders and 67 families), probably because the number of samples in the latter were lower. The number of occasional species, considering those that were captured only in 1 or 2 samples, were 56 in Alboran and 44 in Vera. The multivariate analyses (nMDS) indicated that depth is the main factor that determines the distribution of species in both areas, with four groups of samples displaying significant differences between them (ANOSIM-Alboran: R=0.85, p=0.001; ANOSIM-Vera: R=0.81, p=0.001). These groups were similar in both areas: Inner continental shelf (30-100 m), Outer continental shelf (101-200 m), Upper continental slope (201-500 m) and Middle continental slope (501-800 m) (Figures 2 and 3). Regarding the faunistic comparison between Alboran and Vera, the most acute differences were found between those samples from the Middle continental slope. These differences were evident for abundance (ANOSIM: R=0.81, p=0.001), biomass (ANOSIM: R=0.78, p=0.001) and species composition (presence-absence data) (ANOSIM: R=0.61, p=0.001). The trends for species rarefaction curves with depth was similar in both areas, with similar curves for the Inner and Outer continental shelf , a decrease of the species number for the Upper slope and finally the lowest number of species for the Middle slope. Likewise, the mean values of abundance, Shannon and Taxonomic indices also showed a similar pattern in both areas. Mean abundances differed significantly between assemblages increasing from the Inner shelf to Outer shelf and decreasing abruptly to the Upper and Lower slope (.minimum values). The Shannon diversity index showed significant differences in Alboran, but not in Vera, with minima in the Outer shelf in both areas. The taxonomic index also displayed significant differences in Alboran and Vera, with low values in the Inner shelf that increased abruptly to the Outer shelf and Upper slope, with a further acute increase in the Middle slope. Unlike for the other indexes, trends for mean the biomass values with depth were different in both areas. In Alboran biomass decreased from the Inner shelf to the Upper slope and increased to the Middle slope. Nevertheless, in Vera the biomass decreased with depth, with significant differences. In two sectors were evident significant differences. Regarding the interannual changes, the differences between years in Alboran were significant respect to species richness, abundance, biomass and Shannon diversity index. No clear increase or decrease trend was detected interannually. Unlike Alboran, in Vera, no significant interannual differences were detected. In conclusion: 1) Four main fish assemblages were detected on the continental shelf and slope in both areas that seem to be strongly linked to the depth gradient. 2) The middle slope showed the higher differences between both areas for abundance, biomass and presence-abundance data. 3) The species rarefaction curves, abundance, Shannon and Taxonomic diversity indices showed similar patterns with depth in both areas. Biomass index showed a different pattern, with maximum values in the Middle slope in Alboran and minimum ones in Vera

MAREA PROJECT : MEDISEH (Mediterranean Sensitive Habitats) specific contract no 2 (SI2.600741)

Based on the following Terms of Reference (TOR) of the content of the European Commission DG MARE request Ares (2011)665688: “Compile information supporting the identification and location of nursery areas (juveniles in their first and, if appropriate, second year of life) and spawning aggregations. This information, which is to be collated and archived in formats adequate for GIS rendering, shall refer to all the demersal and small pelagic species in the Mediterranean included in Appendix VII of Council Regulation (EC) No 199/2008 as well as for the species subject to minimum size (Council Regulation (EC) No 1967/2006-Annex III). In addition, ecological characterisation of these areas, both in terms of biological community (assemblage) and habitats therein, must be provided.” The technical tender form of the Specific Contract 2 (MEDISEH) defined the following objectives: Review of historical and current data on the locations and the status of seagrass beds, coralligenous and mäerl beds in different GSAs (Geographical Sub-Areas amending amending the Resolution GFCM/31/2007/2) all over the Mediterranean basin. Transform the information into a digitilized format within the framework of a geodatabase Review and map of all existing specific Marine Protected Areas (MPAs) in the Mediterranean area as well as areas that are under any form of national or international regulation. Identify and map suitable areas for Posidonia, coralligenous and mäerl communities by developing habitat distribution models at different spatial scales. Review and map all existing information on historical and current data of nurseries and spawning grounds of certain small pelagic (i.e., Engraulis encrasicolus, Sardina pilchardus, Scomber spp., Trachurus spp.) and demersal species (i.e., Aristaeomorpha foliacea, Aristeus antennatus, Merluccius merluccius, Mullus barbatus, Mullus surmuletus, Nephrops norvegicus, Parapenaeus longirostris, Pagellus erythrinus, Galeus melastomus, Raja clavata, Illex coindetti, Eledone cirrosa) that are included in the Data Collection Framework for the Mediterranean and subjected to minimum landing size based on Council Regulation No 1967/2006-Annex II. Analyze existing survey data and apply spatial analysis techniques in order to identify locations that are more likely to be density hot spot areas or are being more suitable for fish nurseries and spawning grounds for Engraulis encrasicolus, Sardina pilchardus, Scomber spp., Trachurus trachurus, Aristaeomorpha foliacea, Aristeus antennatus, Merluccius merluccius, Mullus barbatus, Mullus surmuletus, Nephrops norvegicus, Parapenaeus longirostris, Pagellus erythrinus, Galeus melastomus, Raja clavata, Illex coindetti, Eledone cirrosa These areas will also be characterized from an environmental and ecological perspective upon data availability. Integrate and present the aforementioned information through a Web-based GIS viewer with an associated geo-referenced database that will operate as a consulting tool for spatial management and conservation planning. Following the revision of the knowledge base, to identify gaps and suggest future research priorities. In order to meet these objectives, an expert team was composed within the MAREA Consortium from scientists with established expertise in the different topics required, and working in different areas of the Mediterranean basin. The team formed to execute the project includes the main Institutes of EU countries in the Mediterranean, all having solid reputations in the fields covered. The participating Institutes/Entities operate in the Western, Central and Eastern parts of the Mediterranean basin, and this ensures familiarity with the geographical areas that are related to the specific tendering. Moreover, a large number of scientists outside of the MAREA Consortium collaborated on a volunteer basis with data and other input. Details on the list of experts and external collaborators can be found in each Work Package in the present report. For CV details, check the MAREA expert web-site http://www.mareaproject.net/.peer-reviewe

How does climate change affect a fishable resource? The case of the royal sea cucumber (Parastichopus regalis) in the central Mediterranean Sea

Holothurians or sea cucumbers are key organisms in marine ecosystems that, by ingesting large quantities of sediments, provide important ecosystem services. Among them, Parastichopus regalis (Cuvier, 1817) is one of the living sea cucumbers in the Mediterranean actively fished for human consumption mainly in Spain, where it is considered a gastronomic delicacy. In the Strait of Sicily (central Mediterranean Sea), this species is not exploited for commercial use even if it is used as bait by longline fishery. P. regalis is frequently caught by bottom trawling and discarded at sea by fishers after catch, and because of its capacity to resist air exposition (at least in cold months), it is reasonable to consider that it is not affected by fishing mortality. Having observed a significant decrease in abundance since 2018, the possible effects of some ecological factors related to current climate change (i.e., temperature and pH) were sought. Generalized additive models (GAMs) were applied to investigate the relationship among the abundance of P. regalis and environmental variables and fishing effort. Long time series of P. regalis densities (2008-2021) were extracted from the MEDITS bottom trawling survey and modeled as function of environmental parameters (i.e., salinity, dissolved oxygen, ammonium, pH, and chlorophyll alpha) and fishing effort (i.e., total number of fishing days per gross tonnage). Our results showed that this species prefers the soft bottoms (50-200 m) of the Adventure Bank and Malta Plateau, and its distribution changed over time with a slight deepening and a rarefaction of spatial distribution starting from 2011 and 2017, respectively. In addition, a positive relationship with pH concentration in surface waters during the larval dispersal phase (3-year lag before the survey) and nutrient concentration at sea bottom (1-year lag) has been found, suggesting that this species is sensitive to climate change and food availability. This study adds new knowledge about the population dynamics of an unexploited stock of P. regalis under fishing impact and environmental under climate change in fisheries management

Composition and distribution of the larval decapod community in the deep sea of the Western Mediterranean Sea Balearic Sub-basin

Mechanisms facilitating larvae transport from continental to more oceanic areas were investigated in the Balearic sub-basin (BSB), Western Mediterranean Sea. The abundance, distribution, and development stages of decapod larvae were recorded for a transect of 28 stations crossing the central eddy of the BSB. Zooplankton samples were taken to 1,800 m depth by horizontal and oblique 500-μm mesh size nets hauls towed near the benthic boundary (BBL) and in deep scattering layers (DSL). In total, 67 taxa belonging to Decapoda and one Stomatopoda were identified. Advanced development represented 75% of the individuals recorded. 75% of the species corresponded to adults of deep-sea species, 9% were sergestids (mesopelagic species), and the remaining 16% corresponded to shelf and coastal species. Cluster assemblages formed were related to the hydrological conditions, water masses dynamics, and geomorphologic structures mainly associated with nepheloid layers. Advanced and juvenile specimens of commercial species such as Parapenaeus longirostris, Geryon longipes, and Aristeus antennatus were found close to seafloor BBL. The influence of trophic ecology should be considered as the priority factor of larvae concentrations in deep.En prens

Freshening of the Mediterranean Salt Giant: controversies and certainties around the terminal (Upper Gypsum and Lago-Mare) phases of the Messinian Salinity Crisis

The late Miocene evolution of the Mediterranean Basin is characterized by major changes in connectivity, climate and tectonic activity resulting in unprecedented environmental and ecological disruptions. During the Messinian Salinity Crisis (MSC, 5.97-5.33 Ma) this culminated in most scenarios first in the precipitation of gypsum around the Mediterranean margins (Stage 1, 5.97-5.60 Ma) and subsequently > 2 km of halite on the basin floor, which formed the so-called Mediterranean Salt Giant (Stage 2, 5.60-5.55 Ma). The final MSC Stage 3, however, was characterized by a "low-salinity crisis", when a second calcium-sulfate unit (Upper Gypsum; substage 3.1, 5.55-5.42 Ma) showing (bio)geochemical evidence of substantial brine dilution and brackish biota-bearing terrigenous sediments (substage 3.2 or Lago-Mare phase, 5.42-5.33 Ma) deposited in a Mediterranean that received relatively large amounts of riverine and Paratethys-derived low-salinity waters. The transition from hypersaline evaporitic (halite) to brackish facies implies a major change in the Mediterranean’s hydrological regime. However, even after nearly 50 years of research, causes and modalities are poorly understood and the original scientific debate between a largely isolated and (partly) desiccated Mediterranean or a fully connected and filled basin is still vibrant. Here we present a comprehensive overview that brings together (chrono)stratigraphic, sedimentological, paleontological, geochemical and seismic data from all over the Mediterranean. We summarize the paleoenvironmental, paleohydrological and paleoconnectivity scenarios that arose from this cross-disciplinary dataset and we discuss arguments in favour of and against each scenario

The late Miocene – early Pliocene offshore onshore sedimentary records in the vicinity of Gibraltar

[EN] Atlantic gateways, progressively isolating the Mediterranean Basin from the Global Ocean. This change in gateway configuration modified radically the circulation patterns, water residence time and salinity of the Mediterranean waters leading to the extraordinary paleoenvironmental change known as the Messinian Salinity Crisis (MSC). This event lasted between 5.97 and 5.33 Ma and led to the deposition of huge evaporite accumulations both in the marginal and deep Mediterranean basins. Now, more than 50 years after the Glomar challenger ventured Mediterranean waters, and the evaporites in deep basins were discovered, the debate regarding the conditions and timing of the deposition of the Mediterranean salt giant is still ongoing as many theories regarding the dynamics and chronology of the Gibraltar arc gateway/s closure and reopening are waiting to be validated. In this optic, the study of cores and outcrops in the proximity of the current Strait of Gibraltar is essential to better understand the evolution of the Mediterranean – Atlantic gateways. In this thesis we perform a detailed planktic and benthic foraminifer, geochemical (XRF and stable isotopes) and sedimentological analyses of Alboran Basin ODP Site 976, DSDP Site 121, industrial boreholes Andalucia-G1, Alboran-A1, landbased sections from southern Spanish basins including Nijar, Sorbas and Malaga and Montemayor-1 core from the Guadalquivir Basin. The obtained results, paired with the interpretation of seismic profiles acquired in the Alboran Basin gave some new insights and results towards the better understanding of the Late Miocene to early Pliocene evolution of the Mediterranean – Atlantic gateways and the effects of the restriction on the Mediterranean environments before and after the MSC. The main outcomes of this thesis are outlined in the next paragraphs, as follows: → A high-resolution planktonic foraminifer stratigraphy performed on Sites 976 and Montemayor-1 in combination with the analyses of the astronomically driven cyclical changes in the geochemical record enabled the astronomical tuning of the two locations. Having a firm age model allowed to pinpoint the moment when the uplift of the Gibraltar arc gateway/s started affecting the Mediterranean Basin and Betic corridor. → The first sign of the Mediterranean – Atlantic gateway restriction is visible in the Mediterranean basin from 7.17 Ma, when active tectonism at the Gibraltar arc started uplifting the Betic and Rifian corridors. At ODP Site 976, the uplift is visible from the increase in terrigenous input arriving to the Alboran basin and parallel higher sedimentation rates related with an increased river erosion. On the other hand, the shift from benthic foraminifer open-marine high oxygen fauna to shallow infaunal taxa, tolerant to a wide range of conditions and suboptimal oxygen levels, paired with a significant drop in benthic δ13C values suggests that the gateway restriction led to the decrease in bottom water oxygen levels and increase in its residence time much earlier than the onset of the MSC. → A correlation between data from ODP Site 976 and other Mediterranean records confirmed that the 7.17 Ma gateway restriction, affected at the same time different locations all over the Mediterranean, inferring a Mediterranean-scale change in thermohaline circulation. From these data we concluded that the West Alboran Basin (WAB) and the East Alboran Basin (EAB) were not separated by a sill at that time but were both part of the Mediterranean realm. Furthermore, it was possible to create a refined Mediterranean circulation model for before and after the 7.17 Ma event. → The gateway restriction registered in the Mediterranean record since 7.17 Ma, is visible also from the geochemical data of Montemayor-1 core in the Guadalquivir Basin. Because the geochemical data from Montemyor-1 reveals that after 7.15-7.17 Ma, the Guadalquivir Basin was bathed by only one water mass, probably Atlantic, we believe that the connection between the Mediterranean and Atlantic through the Betic corridor was restricted at that time. Consequently, we suggest that the restriction of the last Betic gateway, the Guadalhorce Basin, could have happened at 7.15-7.17 Ma and caused the abovementioned changes in the Mediterranean paleoenvironment. → Because the gateway restriction was contemporaneous with the global Late Miocene Carbon Isotope Shift (LMCIS) it was important to discern between global and local effects and compare the Mediterranean and global records. Given the synchronism of the global and local Mediterranean change in the δ13C record, a global effect certainly affected the Mediterranean Basin. However, opposite phase relations of the global and local δ13C signals with orbital parameters, paired with a higher magnitude change identified in our WAB isotope record suggests that the local imprint overruled the global one. A similar effect can be seen in the Montemayor-1 record, where apart from the changes related to the uplift of the Gibraltar arc, a global signal cannot be overruled. → Finally, through the development of this thesis it is shown how the dark layer often enriched in organic matter, present at the Miocene – Pliocene boundary in several Mediterranean marginal and deep basins, suggests that the Zanclean reflooding created water column stratification, and reduced bottom water oxygen levels. Such stratification could be the result of a sinking of more saline Atlantic water mass entering into a less saline Mediterranean Basin still under the influence of the Paratethys. The benthic foraminifer repopulation sequence identified at the base of the Pliocene shows similarities with more recent events of repopulation of hostile environments or following low-oxic episodes during sapropel deposition. However, Atlantic values of the benthic δ13C registered in the Alboran Basin suggest that bottom water renewal and circulation were efficient during the early Zanclean, preventing the reduction of δ13C at the seafloor seen after 7.17 Ma. Furthermore, the slight discrepancies in the benthic foraminifer repopulation sequences of the marginal basins at the Miocene – Pliocene boundary, and the much lighter benthic δ13C values in the Malaga Basin can suggest a diachronous reflooding of the shallower marginal basins

Preparing for offshore renewable energy development in the Mediterranean

The development of offshore wind farms and marine renewable energy devices in the Mediterranean is central to both national, and international, energy strategies for countries bordering the Mediterranean Sea. The ecological impacts of marine renewable energy development in the Mediterranean region, although essential for policy makers, are as yet unknown. The Northern Adriatic is identified as a plausible site for offshore wind farm development. Using the wider region (Adriatic and Northern Ionian) as a case study, this thesis examines the likely impact to the marine environment if an offshore wind farm is established. Site suitability, based on wind speed, bathymetry, and larvae connectivity levels are investigated along with the plausibility of the turbines operating as artificial reefs in the area. As offshore wind farms may alter the larval connectivity and supply dynamics of benthic populations, a connectivity map was constructed to identify areas of high and low connectivity in the Adriatic Sea. The Puglia coast of Italy is a likely larval sink, and displays some of the highest connectivity within the region, suggesting potential inputs of genetic materials from surrounding populations. Considering offshore wind farms could operate as artificial reefs, an in-situ pilot project was established to simulate the presence of wind turbines. Macroinvertebrates colonized the new substrata within the first few months but were lower in abundance when compared to a natural hard substrata environment. Time, turbine location, and the material used for turbine construction all affected the macro-invertebrate communities. In addition, fish abundances, and diversity were lower around the simulated OWF foundations in comparison to a natural hard substrata environment, and no increases in fish abundance occurred around the simulated turbines when compared to reference sites of soft substrata. This observation was validated with the use of an ecosystem modelling software (Ecopath with Ecosim), which simulated the overall ecosystem level impacts that would occur if 50 offshore monopile wind turbines were introduced to the Northern Ionian and colonized by macroinvertebrate communities. When compared to the baseline scenario (no simulated introduction of an OWF), the introduction of new habitat had no discernible impacts to the structure or functioning of the marine ecosystem. Noticeable changes to the ecosystem were only apparent if fishing restrictions were enforced in parallel with the simulated offshore wind farm; the ecosystem appears to become more structured by top down predation. In addition seabirds are also impacted by the reduction of fishing discards as a food source. These results are the first attempt to quantify the suspected benefits of offshore wind farms operating as de-facto marine protected areas.Hellenic Centre for Marine Researc

Second Workshop on Atlantic chub mackerel (Scomber colias) (WKCOLIAS2)

The Atlantic chub mackerel Scomber colias has become an increasingly important commercial species in the European Atlantic waters in the last 10–15 years, probably through an expansion process from NW African waters and due to market needs. However, at present there are no assessment or advice requirements. In the WK framework, available information of the species in the West Atlantic waters has been compiled in order to evaluate possible geographical differences and trends, and the feasibility to describe its population structure. Though the Atlantic chub mackerel is not routinely included among the target species in the acoustic surveys performed in the Atlantic Iberian waters and the Mediterranean Sea, a synoptic overview of the species is possible over all its West Atlantic distribution. Moreover, the data available have indicated latitudinal trends, mainly in the landings’ length composition, L50 and the spawning periods. Nevertheless, even if some degree of connectivity likely exists and migrations are occurring between adjacent areas, some subunits could be considered for management purposes. From the assessment models’ trials carried out, the results or reference points obtained for the European fisheries cannot be retained at present. Therefore, continuing collating information from fisheries and biological sampling of the species, obtaining reliable biomass estimations from scientific surveys and identifying management units seem the main priorities to address in future research work and in case of assessment requirements

Scientific, Technical and Economic Committee for Fisheries (STECF) – Mediterranean assessments part 1 (STECF-15-18).

The Expert Working Group meeting of the Scientific, Technical and Economic Committee for Fisheries EWG 15-11 was held from 31 Aug-04 Sep 2015 in Palma de Mallorca, Spain to assess the status of demersal and small pelagic stocks in the Mediterranean Sea against the proposed FMSY reference points. The report was reviewed by the STECF plenary in November 2015.JRC.G.3-Maritime affair