Massimiliano Bottaro

Chondrichthyans are among the most threatened vertebrate groups worldwide, yet their ecology and long-term trajectories remain poorly understood in data-limited regions such as the Mediterranean Sea. This study used Local Ecological Knowledge (LEK) provided by fishers to investigate perception-based temporal changes in the reported composition of chondrichthyan taxa across Italian waters. A total of 57 semi-structured interviews were conducted across multiple Geographical Sub-Areas, collecting information on reported taxon occurrence, perceived abundance trends, and temporal contrasts between earlier and more recent phases of fishers’ careers. Overall, 35 taxa were reported. The number of taxa reported was significantly higher for the present than for the past. Rather than indicating a real increase in biodiversity, this pattern is more plausibly interpreted as a shift in ecological perception, potentially influenced by shifting baselines, changes in detectability, evolving fishing practices, and improved taxonomic awareness. Taxon-level analyses showed contrasting patterns, with some taxa increasing in reporting frequency, whereas others, such as Squatina squatina, declined markedly in contemporary reports. Anecdotal recollections of large catches and large individuals were consistent with fishers’ perceptions of historically more frequent encounters and body sizes, although these accounts should be interpreted as qualitative evidence. Several frequently reported taxa are currently classified as threatened, highlighting a mismatch between perceived commonness and conservation status. These findings show that LEK primarily reflects ecological perception and memory and should therefore be integrated with conventional data sources to support chondrichthyan conservation in the Mediterranean Sea.

Commercial smooth-hound sharks of the genus Mustelus are commonly landed and consumed in Mediterranean fisheries, raising concerns about potential human exposure to persistent contaminants. This study investigated the occurrence of organochlorine compounds (OCs), including hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polychlorinated biphenyls (PCBs), together with per- and polyfluoroalkyl substances (PFAS), in muscle and liver tissues of Mustelus mustelus and Mustelus punctulatus collected in the waters of the Egadi Archipelago (central Mediterranean Sea). OCs were detected in all analyzed samples, with total PCB concentrations reaching higher values in liver compared to muscle tissues, reflecting tissue-specific accumulation and detoxification processes. PFAS were detected in all analyzed muscle samples (1.10–58.5 ng/g w.w.), with PFOS, PFOA and PFNA generally below current European regulatory thresholds, although isolated exceedances were observed. Stable isotope analysis (δ¹³C and δ¹⁵N) highlighted differences in trophic ecology between the two species and suggested that feeding habitat and trophic position may influence contaminant exposure patterns, particularly in M. punctulatus. The human health risk assessment, conducted as a screening-level evaluation, indicated potential concern associated with PCB concentrations in liver tissue, while risks associated with muscle consumption were generally lower. Overall, the integration of contaminant analysis and stable isotopes provides insights into organismal exposure pathways and supports the use of smooth-hound sharks as sentinels of contaminant presence in Mediterranean coastal ecosystems.

The blue shark ( Prionace glauca ) is a widely distributed pelagic predator that undergoes ontogenetic morphological changes that reflect ecological and functional adaptations. Investigating this aspect could provide powerful tools for elucidating the patterns of trait variation and their significance in relation to environmental conditions. This study explores morphometric variation and its ecomorphological implications in the Mediterranean blue shark population using linear and geometric morphometric analyses. A total of 119 specimens (64 females, 55 males), spanning from juvenile (total lengths [TLs] 85.4–149.8 cm in females and 82.9–121.2 cm in males) to adult (TLs 150.4–333.1 cm in females and 133.2–206.8 cm in males) stages, were analysed through a set of 30 linear measurements. Linear morphometric analysis identified significant differences between the juvenile and subadult/adult groups, particularly in the anterior body region and pectoral fin measurements. Geometric morphometric results revealed that juveniles have a more heterocercal caudal fin shape, which transitions to a less heterocercal form in adults, with a proportionally larger ventral lobe. The first dorsal fin showed positive allometry, becoming higher. The observed ontogenetic differences could improve energy efficiency and manoeuvrability. This aligns with the diel vertical migrations (DVM) of larger individuals and their need for sustained swimming during long‐distance migrations, as well as the enhanced manoeuvrability required by juveniles, notably for predator avoidance. These morphological changes likely reflect adaptations to changing energy requirements and locomotion needs throughout life stages. Although blue sharks maintain a generalist diet across ontogeny, these adaptations may optimise feeding efficiency and swimming performance, particularly in adults. This study highlights the interplay between ontogeny, morphology and ecological function, shedding light on the selective pressures that shape the life history strategies of blue sharks. The findings emphasise the importance of integrating ontogenetic perspectives into ecomorphological studies to better understand the evolutionary adaptations of pelagic sharks.

The Mediterranean Sea, a biodiversity hotspot classified by the IUCN as critically threatened for sharks and rays, faces significant conservation challenges because of geopolitical complexities. Traditional, top‐down management strategies often fail, thus calling for alternative conservation approaches. This study documents the first recorded catch and release of a juvenile great white shark (Carcharodon carcharias) off Lampedusa Island (Central‐Southern Mediterranean Sea), facilitated by the EU‐cofunded LIFE ELIFE project. This successful release, achieved through collaboration between scientists and local fishers, underscores the importance of stakeholder involvement and cooperative strategies in conserving endangered elasmobranchs in the Mediterranean.

Marine ecosystems are increasingly threatened by pollutants, including trace elements (TEs) such as heavy metals, which bioaccumulate and pose risks to both marine fauna and human health. Sharks and rays are particularly susceptible to metal uptake and retention, making them sentinel species for assessing environmental contamination. This study investigated the bioaccumulation of 16 TEs across 12 elasmobranch species sampled from the Ionian and Tyrrhenian coasts of Calabria, southern Italy, over an 11-year period. Muscle tissue was analyzed for all species, while additional comparisons among skin, muscle, and brain tissues were conducted for Galeus melastomus. Statistical analyses revealed significant variability in TEs concentrations across trophic levels (TRLs), with higher levels observed in species occupying higher trophic positions. Positive correlations were noted for elements such as Al, Ba, and Se, while negative correlations were found for Co, Cu, Mn, and U, indicating species-specific metabolic adaptations. Tissue-specific analyses identified the skin as a primary site for TEs accumulation, likely due to its barrier functions and external exposure. This study highlights the complex interplay of ecological, dietary, and physiological factors influencing TEs bioaccumulation in elasmobranchs and emphasizes the need for further research to understand the implications for marine food webs and conservation strategies.

Cartilaginous fish face significant threats due to overfishing and slow reproductive rates, leading to rapid declines in their populations globally. Traditional capture-based surveys, while valuable for gathering ecological information, pose risks to the health and survival of these species. Baited Remote Underwater Video Systems (BRUVS) offer a non-invasive alternative, allowing for standardized surveys across various habitats with minimal disturbance to marine life. This study presents a comprehensive review of BRUVS applications in studying cartilaginous fish, examining 81 peer-reviewed papers spanning from 1990 to 2023. The analysis reveals a significant increase in BRUVS usage over the past three decades, particularly in Australia, South Africa, and Central America. The most common BRUVS configurations include benthic setups, mono-camera systems, and the use of fish from the Clupeidae and Scombridae families as bait. BRUVS have been instrumental in studying 195 chondrichthyan species, providing insights into up to thirteen different aspects of the life histories. Moreover, BRUVS facilitate the monitoring of endangered and data-deficient species, contributing crucial data for conservation efforts. Overall, this study underscores the value of BRUVS as a powerful tool for studying and conserving cartilaginous fish populations worldwide.