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Investigating marine species population structure in a multidisciplinary framework can reveal signatures of potential local adaptation and the consequences for management and conservation. In this study we delineate the population structure of common sole (Solea solea) in the Mediterranean Sea using genomic and otolith data, based on single nucleotide polymorphism (SNPs) markers, otolith shape and otolith trace element composition data. We correlated SNPs with environmental and spatial variables to evaluate the impact of the selected features on the actual population structure. Specifically, we used a seascape genetics approach with redundancy (RDA) and genetic-environmental association (GEA) analysis to identify loci potentially involved in local adaptation. Finally, putative functional annotation was investigated to detect genes associated with the detected patterns of neutral and adaptive genetic variation. Results from both genetic and otolith data suggested significant divergence among putative populations of common sole, confirming a clear separation between the Western and Eastern Mediterranean Sea, as well as a distinct genetic cluster corresponding to the Adriatic Sea. Evidence of fine-scale population structure in the Western Mediterranean Sea was observed at outlier loci level and further differentiation in the Adriatic. Longitude and salinity variation accounted for most of the wide and fine spatial structure. The GEA detected significant associated outlier loci potentially involved in local adaptation processes under highly structured differentiation. In the RDA both spatial distribution and environmental features could partially explain the genetic structure. Our study not only indicates that separation among Mediterranean sole population is led primarily by neutral processes because of low connectivity due to spatial segregation and limited dispersal, but it also suggests the presence of local adaptation. These results should be taken into account to support and optimize the assessment of stock units, including a review and possible redefinition of fishery management units. [ABSTRACT FROM AUTHOR]

Spatial fisheries management is widely used to reduce overfishing, rebuild stocks, and protect biodiversity. However, the effectiveness and optimization of spatial measures depend on accurately identifying ecologically meaningful areas, which can be difficult in mixed fisheries. To apply a method generally to a range of target species, we developed an ensemble of species distribution models (e‐SDM) that combines general additive models, generalized linear mixed models, random forest, and gradient‐boosting machine methods in a training and testing protocol. The e‐SDM was used to integrate density indices from two scientific bottom trawl surveys with the geopositional data, relevant oceanographic variables from the three‐dimensional physical‐biogeochemical operational model, and fishing effort from the vessel monitoring system. The determined best distributions for juveniles and adults are used to determine hot spots of aggregation based on single or multiple target species. We applied e‐SDM to juvenile and adult stages of 10 marine demersal species representing 60% of the total demersal landings in the central areas of the Mediterranean Sea. Using the e‐SDM results, hot spots of aggregation and grounds potentially more selective were identified for each species and for the target species group of otter trawl and beam trawl fisheries. The results confirm the ecological appropriateness of existing fishery restriction areas and support the identification of locations for new spatial management measures. [ABSTRACT FROM AUTHOR]

Deep-sea fishery in the Mediterranean Sea was historically driven by the commercial profitability of deepwater red shrimp (DWRS), and understanding spatiotemporal dynamics of fishing is key to comprehensively evaluate the status of these profitable resources and prevent stock collapse. A 4-year time series of observed monthly patterns and related frequency of trawling disturbance based on an automatic identification system (AIS) is provided with a resolution of 0.01∘×0.01∘ , accounting for the spatial extent and temporal variability in deepwater (DW) bottom-contact fisheries during the period 2015–2018. The dataset was estimated from 370 fishing vessels that were found to perform trawling in deep water (400–800 m) during the study period, and they represent a significant part of the real fleet exploiting these fishing grounds in the study area. The reconstructed deepwater trawling-effort dataset is available at: 10.17882/89150 (Pulcinella et al., 2022). This large-scale and high-resolution dataset may help researchers of many scientific fields, as well as those involved in fishery management and in the update of existing management plans for deepwater red shrimp fisheries as foreseen in relevant recommendations of the General Fisheries Commission for the Mediterranean (GFCM). [ABSTRACT FROM AUTHOR]

Deep-sea fishery in the Mediterranean Sea was historically driven by the commercial profitability of deepwater red shrimps and understanding spatio-temporal dynamics of fishing is key to comprehensively evaluate the status of these profitable resources and prevent stock collapse. A four-year time series of AIS-based observed monthly patterns and related frequency of trawling disturbance are provided with a resolution of 0.01°*0.01°, accounting for the spatial extent and temporal variability in deep water bottom contact fisheries during the period 2015-2018. The dataset was estimated from 370 fishing vessels that were found to perform trawling in deep water (400 m - 800 m) during the study period, and they represent a significant part of the real fleet exploiting this fishing grounds in the study area. The reconstructed deep-water trawling effort dataset is available at: https://doi.org/10.17882/89150 (Pulcinella et al., 2022). This large-scale and high-resolution dataset may help researchers of many scientific fields, as well as those involved in fishery management and in the update of existing management plans for deep-water red shrimp fisheries as foreseen in relevant General Fisheries Commission for the Mediterranean (GFCM) recommendations. [ABSTRACT FROM AUTHOR]

Knowledge of connectivity among subpopulations is fundamental in the identification of the appropriate geographical scales for stock status evaluation and management, the identification of areas with greater retention rates, and space‐based fisheries management. Here, an integration of hydrodynamic, biological, and habitat models results is used to assess connectivity and support the definition of essential fish habitats (EFH) in the Adriatic Sea, with reference to Nephrops norvegicus, an important benthic commercial resource, the recruitment of which is strongly related to larval dispersal from spawning to recruitment areas. We explored oceanographic and biological connectivity in the Adriatic Sea under a wide and representative variety of oceanographic conditions (winters 2006–2012) by tracking 3D trajectories of larvae released from different areas. We used a Lagrangian model that features a specific larval behavior module with explicit dependence on environmental parameters (i.e., temperature and sediment type) and that is driven by high‐resolution hydrodynamic and meteorological data. The results were used to partition the area in which Nephrops was observed into 20 homogenous management subareas; to assess the connection between spawning, recruitment, and harvesting grounds; and to identify potential subpopulation boundaries as well as the connectivity among the potential subpopulations. The results suggest the presence of at least three distinct subpopulations, which need to be independently managed and conserved, and confirms that the Jabuka‐Pomo pit is the most important spawning area, but alone it cannot sustain Nephrops populations throughout the Adriatic Sea. The results also show the importance to move from particle‐tracking to approaches based on integrated models. [ABSTRACT FROM AUTHOR]

A growing concern about the depletion of marine resources due to fishing overexploitation and degradation of ecosystems has been demonstrated over the last decade. Monitoring the spatial and temporal distribution of fishing activities is an important tool for fisheries management which can also be used by other sectors such as fisheries science, public authorities, policy-makers and marine spatial planning. In this paper we introduce the first map of fishing activity at a Mediterranean scale of EU and non-EU fishing vessels, extracted using Automatic Identification System ship tracking data. Fishing activity maps were produced for three different years with a spatial resolution of 0.01° × 0.01°. As a main result, for the first time, changes of bottom trawl fishing activities between two consecutive years were map for the whole Mediterranean Sea. The results confirmed the suitability of this monitoring system to obtain reliable information on the extent of bottom trawl fishing activities. [ABSTRACT FROM AUTHOR]

Small-Scale Fishery (SSF) is recognized as one of the more sustainable among the activities currently exploiting marine renewable resources. This is mainly due to the use of fishing gears characterised by a low environmental impact and a high selectivity. However, there is still room for improvement when analysing the sustainability of SSF sector. Within this context, Greenhouse Gases (GHG) emissions – CO 2 in particular – are one of the most relevant aspect to be considered. In particular, fuel consumption and its reduction represent the main issue when discussing sustainability, especially to cope with climate changes. In this paper, the first inventory of CO 2 emissions from the SSF vessels in the Central-Northern Adriatic Sea (GSA17) has been compiled, based on data collected from SSF operators, validated by means of a geospatial-based method. Emission intensity estimates – 7.01 kg of CO 2 emitted per kg of landing or 2.08 kg of CO 2 emitted per € of landing – confirmed the lower values by SSF vessels in comparison with other fleet segments. Results are discussed in the light of the mitigation of GHG emissions for the SSF, considering the technological features of Adriatic SSF, fishers' behaviour and an improved management of the fishery. [ABSTRACT FROM AUTHOR]

Independence of science and best available science are fundamental pillars of the UN-FAO code of conduct for responsible fisheries and are also applied to the European Union (EU) Common Fishery Policy (CFP), with the overarching objective being the sustainable exploitation of the fisheries resources. CFP is developed by DG MARE, the department of the European Commission responsible for EU policy on maritime affairs and fisheries, which has the Scientific, Technical and Economic Committee for Fisheries (STECF) as consultant body. In the Mediterranean and Black Sea, the General Fisheries Commission for the Mediterranean (FAO-GFCM), with its own Scientific Advisory Committee on Fisheries (GFCM-SAC), plays a critical role in fisheries governance, having the authority to adopt binding recommendations for fisheries conservation and management. During the last years, advice on the status of the main stocks in the Mediterranean and Black Sea has been provided both by GFCM-SAC and EU-STECF, often without a clear coordination and a lack of shared rules and practices. This has led in the past to: i) duplications of the advice on the status of the stocks thus adding confusion in the management process and, ii) a continuous managers' interference in the scientific process by DG MARE officials hindering its transparency and independence. Thus, it is imperative that this stalemate is rapidly resolved and that the free role of science in Mediterranean fisheries assessment and management is urgently restored to assure the sustainable exploitation of Mediterranean marine resources in the future. • Advice on the status of the main stocks in the Mediterranean and Black Sea is provided both by GFCM-SAC and EU-STECF. • Duplication of the advice on the status of Mediterranean and Black Sea stocks creates confusion in the management process. • Continuous interference in the scientific process by DG MARE officials has hindered its transparency and independence. • It is imperative that this stalemate is resolved and that the free role of science in Mediterranean fisheries is restored. [ABSTRACT FROM AUTHOR]

Stock identification studies are essential to understanding fish population structure and connectivity across wide geographical areas, and thus contribute to efficient fisheries management. The blackbelly rosefish, Helicolenus dactylopterus , and European hake, Merluccius merluccius , are two economically important marine fishes, but there are still gaps in knowledge regarding their present stock structure. Our objective was to assess the ability of otolith shape to define stock structure for the two species along the Northeastern Atlantic Ocean and the Mediterranean Sea, based on samples from eight and seven areas, for blackbelly rosefish and European hake, respectively. Shape analysis was obtained through Wavelet analysis. Canonical analysis of principal coordinates provided significant evidence for different population units with a clear separation between the Atlantic and Mediterranean populations for both species. However, random forest procedures indicated that the discrimination power varied with species and locations. For blackbelly rosefish, various Atlantic populations were more evident than for European hake. Overall, the usefulness of otolith shape to delineate stock structure of two species with distinct life history traits across a broad spatial region from the mid-Atlantic isles to the polar region, as well as the Mediterranean was demonstrated. Moving forward, it will be key to align our growing understanding of population structure with our increasing knowledge on species' biological traits to ensure management units reflect population structure. [Display omitted] • Helicolenus dactylopterus and Merluccius are fishery exploited species. • We used otolith shape to define their stock structure in the Atlantic and Mediterranean. • Wavelet analysis and canonical analysis of principal coordinates revealed diverse population units. • Random forests showed that the discrimination power varied with species and locations. • Results suggest a higher degree of connectivity of M. merluccius in the Atlantic. [ABSTRACT FROM AUTHOR]

In the Adriatic Sea two cryptic species of sole coexist, the common and Egyptian sole. Soles are one of the most valuable demersal fishery resources in the Adriatic Sea, so a correct species identification is crucial in order to perform stock assessment and implement effective management measures based on reliable and accurate data. In this study specimens collected during fishery-independent and fishery-dependent activities in the Adriatic were analyzed and identified coupling morphological and genetic approaches. A comparison of these two methods for the sole species identification was carried out to assess the most effective, accurate and practical diagnostic morphological key-character(s). Results showed that external characters, in particular features of the posterior dorsal and anal fins, are valid and accurate morphological markers. Based on these traits, a practical identification key of the two sibling species was proposed. Moreover, it was possible to estimate the extent of the error due to species misidentification introduced in the common sole stock assessment carried out in the Northern-central Adriatic Sea (GSA17). A 5% bias in the correct identification of common sole specimens was detected. However, this bias was shown not to affect the common sole stock assessment. Moreover, the genetic profiling of the Adriatic common sole allowed estimating genetic diversity and assessing population structure. Significant divergence between common soles inhabiting the eastern part of the Southern Adriatic Sea and those collected from the other areas of the basin was confirmed. Therefore, the occurrence of genetically differentiated subpopulations supports the need to implement independent stock assessments and management measures. [ABSTRACT FROM AUTHOR]

Fishing of Nassarius mutabilis is by far the most important activity carried out by artisanal fisheries in the central and northern Adriatic Sea, accounting for more than 35% of total fishing effort and yielding from 2000 to 3000 t of landings each year. This gastropod is targeted from the beginning of autumn to the end of spring using basket traps. Despite its importance under a socioeconomic point of view, the scientific studies on the biology and ecology of this species are very scarce and the failure of the current management measures could also be attributed to the scarce knowledge on the biology of this species in the area. Taking this statement into consideration, the results of the present study contribute to fill a few existing gaps and may be useful to improve the management measures currently in force. Samples were collected from March 2006- March 2008 during monthly fishing surveys and carried out using basket traps in the central Adriatic Sea. A total of 383 males (size range 7-29 mm SH) and 504 females (size range 15-32 mm SH) were caught. Mean SH (± SD) of males was 15.84±3.57 mm and mean SH of females was 25.31±3.06 mm. A significant difference in the biometric characteristics between the two sexes was discovered. The condition index (CI) showed similar seasonal trends for both sexes, with a decrease from late winter to spring followed by an increase from summer to fall - early winter. The minimum values were recorded in summer and the maximum ones in winter, following an opposite trend in respect to water temperature. In the males this trend was observed starting from size classes larger than 11 mm SH, hence this size might be very close to the size at first sexual maturity. The size at first maturity hypothesized for females (16-20 mm SH) agrees with the minimum landing size (MLS) currently established for this species (20 mm SH). The absence of small females (SH < 15 mm) and large males (SH > 23 mm) leads to suppose a sex reversal from male to female at around 20 mm SH. On this basis, the management measure of MLS leads to the selective retention of females and, hence, to a sexual gap between the two sexes with possible consequences on the biology of the species and the resilience of the stock. The peaks of CI observed for males and females confirmed that the spawning season of this gastropod occurs in late winter - early spring, according to the abundant presence of egg capsules attached to submerged substrates in that period at sea. Consequently, from a management point of view, it would be advisable to shorten the fishing season that at present extends from fall to later spring. [ABSTRACT FROM AUTHOR]

Experimental fishing trials were carried out on an Italian commercial vessel to test gillnets of different monofilament diameters targeting common sole ( Solea solea ). The gillnets only differed in the nominal monofilament diameter: 0.18, 0.20, 0.22, 0.25, and 0.30 mm. The nominal mesh size (stretched) was 72 mm. A total of 47 taxa were caught. The mean number of species caught with 0.30 mm monofilament was significantly lower than those obtained with the three thinnest diameters. Total number, number of commercial and discard of non-commercial species significantly decreased with the increase of monofilament diameter. The number of common sole and tub gurnard caught was not statistically different amongst diameters. No statistical differences were observed for the length–frequency distributions of common sole and tub gurnard caught with the different monofilament diameters. The analysis of the mechanism of capture for the common sole showed that for all diameters the main type of retention was snagging, and the percentage of individuals retained in such way decreased with the increase of diameters, while an opposite trend was observed for the common sole that were gilled. Monofilament thickness had a substantial effect upon the catch rates of the gillnets. [ABSTRACT FROM AUTHOR]

An ecological niche modelling (ENM) approach was developed to model the suitable habitat for the 0-group European hake, Merluccius merluccius L., 1758, in the Mediterranean Sea. The ENM was built combining knowledge on biological traits of hake recruits (e.g. growth, settlement, mobility and feeding strategy) with patterns of selected ecological variables (chlorophyll-a fronts and concentration, bottom depth, sea bottom current and temperature) to highlight favourable nursery habitats. The results show that hake nurseries require stable bottom temperature (11.8–15.0 °C), low bottom currents (<0.034 m s −1 ) and a frequent occurrence of productive fronts in low chlorophyll-a areas (0.1–0.9 mg m −3 ) to support a successful recruitment. These conditions mostly occur recurrently in outer shelf and shelf break areas. The prediction explains the relative balance between biotic and abiotic drivers of hake recruitment in the Mediterranean Sea and the primary role of unfavourable environmental conditions on low recruitment in specific years (i.e. 2011). The ENM outputs particularly agree spatially with biomass data of recruits, although processes such as fishing and natural mortality are not accounted for. The seasonal mapping of suitable habitats provides information on potential nurseries and recruitment carrying capacity which are relevant for spatial fisheries management of hake in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]