The Antarctic silverfish (Pleuragramma antarcticum) is a key species in the Southern Ocean ecosystem, playing a crucial role in energy transfer between lower and higher trophic levels. Its early life stages are potentially threatened by climate change, and therefore, assessing natal origins and larval connectivity can be crucial for planning management strategies for this species. However, studies investigating population structure and connectivity are still extremely limited. Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, we examined the chemical composition of 172 otoliths from larvae collected in 20 stations in the coastal waters of Terra Nova Bay and Bay of Whales (Ross Sea, Antarctica). We analysed the otolith core and edge to reconstruct environmental exposure during early development and later larval stages. Elemental signatures in the otolith cores revealed the presence of 22 clusters (probably suggestive of natal origins): eight exclusive to the Bay of Whales, three of Terra Nova Bay, and eleven shared between the areas. The age composition of shared clusters revealed spatial differences in hatching patterns, pointing to variable retention dynamics between areas. These findings suggest multiple, coexisting natal origins of P. antarcticum across the Ross Sea, further supporting the role of Bay of Whales as a spawning/hatching ground. By identifying both unique and shared chemical signatures and linking them to larval age structure, this study advances our understanding of larval dispersal and connectivity in this key species. These insights are essential for informing future biodiversity monitoring efforts and supporting conservation strategies under environmental change.

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.

Understanding population connectivity in the marine realm is crucial for conserving biodiversity, managing fisheries, and predicting species responses to environmental change. This is particularly important in Antarctic waters, where unique evolutionary histories and extreme conditions shape marine biodiversity. The longfin icedevil Aethotaxis mitopteryx is an elusive notothenioid fish endemic to Antarctic waters. To explore population connectivity in A. mitopteryx, we used RAD-seq to investigate the genetic differentiation of two populations, one from the Eastern Weddell Sea and the other from the Eastern Antarctic Peninsula, two regions of ecological relevance greatly impacted by climate change. Despite spatial separation, analyses revealed no significant genetic differentiation between the two populations, suggesting extensive gene flow. A pronounced genetic distinction was, however, observed between males and females. This differentiation was largely localized to a specific chromosome, implying a genetic sex determination system with males being the heterogametic sex. These findings contribute novel insights into the genetic structure of A. mitopteryx populations and expand our understanding of genetic mechanisms in Antarctic fish. This study provides a foundation for further investigations into the evolutionary and ecological implications of sex chromosome differentiation in extreme environments.

The slender scalyhead Trematomus lepidorhinus and the scaly rockcod T. loennbergii are closely related species with similar streamlined body morphology, epibenthic lifestyle and ecological niche. They are distributed in relatively deep waters on the continental shelf and slope of the Weddell Sea, although with some differences in preferential depth of occurrence. As previously reported, the peak of abundance of T. loennbergii (600–800 m) is generally deeper than that of T. lepidorhinus (200–500 m). In the present study, we investigated the role of depth as environmental factor in shaping key life history traits of these species, such as longevity and fecundity. Based on age estimates through otolith readings, males and females of T. loennbergii attained 15 and 20 years, whereas males and females of T. lepidorhinus attained 11 and 12 years, respectively. In both species, growth trajectories differed between sexes, although the growth performance was similar. Matching our and previous data on total and relative fecundities, T. loennbergii spawned a lower number of larger eggs per female and mass unit than T. lepidorhinus. Moreover, they adopted different reproductive strategies, as T. loennbergii likely spawned and hatched in autumn and early spring whereas T. lepidorhinus spawned and hatched in winter and early summer, respectively. In agreement with more general trends reported elsewhere in other fish communities, species living in deeper waters are characterized by longer life span and reduced fecundities.

Antarctic notothenioid fish form an adaptive radiation that diversified in the Southern Ocean over the past 10 million years. The biology and life history of about a third of notothenioids have been studied, however, most frequently from a single location. Because species distributions can be discontinuous and depend on environmental conditions, local populations might differ substantially both genetically and phenotypically from distant conspecifics. Among notothenioids, the 15 Trematomus species diversified to occupy environments ranging from subsurface cryopelagic habitats to the deep sea and many Trematomus species likely have circumpolar distributions. Here, we analyzed life history traits of the notothen Trematomus scotti from two distinct geographic areas: Andvord Bay, a fjord on the Western Antarctic Peninsula, and the Weddell Sea at the edge of pack ice zones. These two populations inhabit drastically different areas with important differences in environmental conditions driven by latitude, temperature and ice cover, thus enabling the study of the effects of the environment on life history traits. We first found no evidence for substantial genetic heterogeneity based on the mitochondrial marker mt-co1. Fish in Andvord Bay, however, grew faster and reached longer sizes than congeners in the Weddell Sea. Furthermore, females in Andvord Bay had higher fecundity but produced smaller eggs compared to females in the Weddell Sea. Thus, these two populations of T. scotti displayed distinct life histories likely in response to local environmental conditions. Local life history traits such as these are crucial to consider to evaluate the vulnerability of a species to environmental change.

The composition of the larval fish assemblages in the Ross Sea is relatively well known, especially in the western sector. One of the most abundant icefish is Dacodraco hunteri (Channichthyidae), although it is considered a rare species as an adult. In the present study, we aimed at assessing aspects of the early life history of this species, such as age, hatching period, growth rate and feeding habits, and comparing samples collected in the eastern and western sectors of the Ross Sea. Individual age estimates were obtained by otolith microincrement counts and body growth was described by an exponential model. Diet composition was inferred from stomach content analysis. Fish samples consisted of yolk-sac and preflexion larval stages of development, with an estimated age range of 49–80 days. Growth rates were similar in both sectors of the Ross Sea ranging between 0.18 and 0.19 mm/day, which corresponded to a daily increase of 1.07–1.08

Early life stages of fish represent a key component in the food chain of the pelagic ecosystem of the Southern Ocean, connecting producer trophic levels to those of higher predators. Pelagic larvae and early juveniles of notothenioid fishes overwhelmingly dominate the ichthyoplankton community living on the continental shelf. Scientific research surveys targeting early life stages of fish in the pelagic realm have been mainly carried out in the western Ross Sea, whereas the eastern side can be considered unexplored. As source of high primary production, the presence and timing of formation of wide ice-free areas throughout the year in the Ross Sea play a fundamental role in structuring larval fish community. The Ross Ice Shelf Polynya (RISP) is a large coastal polynya, which is driven and maintained by local prevailing winds and oceanic currents. In the present study, we report the first data on species composition, relative abundance and spatial distribution of larval fish community found off the Bay of Whales in the eastern Ross Sea. As reported for other areas of the Ross Sea, the Antarctic silverfish Pleuragramma antarcticum was by far the most abundant species, followed by other nototheniids and channichthyids in smaller amounts. The huge abundance of P. antarcticum early larvae supports the hypothesis of a potential nursery area near the Bay of Whales. Present results strongly advocate for future investigations in these poorly known and remote areas.

Hybridization and introgression are recognized as mechanisms promoting genetic variability during evolutionary radiations. We examined the impact of introgression in the process of speciation, focusing on the Antarctic icefish genus Chionodraco. Our analyses confirmed that the three Chionodraco species (Chionodraco hamatus, Chionodraco myersi, and Chionodraco rastrospinosus) were genetically distinctive, despite signals of past interspecific gene flow between C. hamatus and C. myersi that likely occurred during interglacial periods. However, in this study, no recent hybrids were identified. The lack of contemporary hybridization may be due to life-history traits and the type of marker used in the analysis. Our study emphasizes the importance of genomic approaches to detect subtle patterns of past hybridization accurately and highlights the significance of historical climate events in the demographic and evolutionary history of Antarctic notothenioids. Polar regions, and especially the Antarctic Peninsula, are now experiencing the fastest climate changes due to global warming. Understanding the impact of past climate events is fundamental to trace current modifications in species' genetic variability and distributions and predict future evolutionary trajectories. This knowledge is also vital for conservation efforts, including the implementation of marine protected areas.

Despite the general belief that the Southern Ocean harbors low fish biodiversity, the Weddell Sea hosts one of the richest fish communities in the region. Parallelly, the Weddell Sea is also known for the presence of dense and diverse macrobenthos. Most macrobenthic invertebrates, such as gorgonians, sponges and bryozoans, are considered ecosystem engineers as they generate a three-dimensional structure that increases habitat heterogeneity. This structural complexity serves as a refuge against predators as well as a nursery ground for many organisms, including fish species. By analyzing video transects recorded by a Remotely Operated Vehicle, we investigated density, spatial distribution and size-frequency of populations of the demersal fish species inhabiting macrobenthic communities in the southernmost part of the Weddell Sea. We also attempted to unveil whether there is any relationship between benthic and fish communities and substrate, as well as some fish behavioral patterns. The dominance of juveniles in the surveyed fish assemblages provides evidence that, at this life stage, some fish species appear to be positively associated with complex benthic communities conformed by bryozoans, sponges and gorgonians which are more common in sand matrix with sparse rocks substrates. Moreover, about 37% of all specimens recorded were resting on benthic invertebrates or were using them to hide, implying that Antarctic benthic communities might offer suitable habitat. As such, it can be concluded that there was an apparent relationship between certain species of fish and the different benthic communities, yet the exact triggers and/or factors behind such an association remain partially elusive.

Accurate species identification is essential to assess biodiversity and species richness in ecosystems threatened by rapid and recent environmental changes, such as warming in most Antarctic waters. The Lepidonotothen species complex comprises demersal notothenioid fishes which inhabit the shelf areas of the Antarctic Peninsula, the Scotia Arc and sub‐Antarctic islands with a circum‐Antarctic distribution. Species determination in this group has often been problematic. In particular, whether Lepidonotothen squamifrons and Lepidonotothen kempi are valid as separate species has been questioned. In this study, we analysed the genetic variation among four nominal southern polar species within this complex ( L. kempi , L. squamifrons , Nototheniops larseni , Nototheniops nudifrons ) by means of three different markers ( ND2 and tRNA mitochondrial genes and a panel of 16 nuclear microsatellites). We tested whether individuals morphologically assigned to L. kempi showed genetic separation from L. squamifrons . Our analyses indicated a lack of differentiation between L. kempi and L. squamifrons . However, a genetically distinct population was found for L. squamifrons at the Shag Rocks islands near South Georgia. Antarctic and sub‐Antarctic islands are known to be home to many cryptic species and further studies will elucidate if the genetically differentiated population we found potentially originated from this context and can be considered an incipient species. Our analysis contributes to further characterize the species composition of the most abundant fish suborder in the Southern Ocean, which is among the regions most threatened by climate change.

The life history traits of many large-sized and commercial Antarctic icefishes are reasonably well known, except for smaller species such as Pagetopsis maculata Barsukov and Permitin, 1958. Therefore, we provide, for the first-time, data on growth and reproductive biology of this species based on a representative sample collected in the Weddell Sea during summer. Individual age and gonad stage of development were assessed by sagittal otolith readings and histological analysis of gonads respectively. The sampled population had an equal sex ratio and was composed of adult specimens spread over a wide size range. Both sexes exhibited isometric body growth and comparable condition factors. The estimated life span and growth parameters were similar between sexes, although females attained a larger asymptotic size than males, consistent with the length-frequency distributions. Typically, the reproductive investment of females, based on the gonadosomatic index, was larger than in males, although they both attained sexual maturity at a similar size. Most individuals were at an advanced stage of gonad maturity, indicating imminent spawning in late summer-early autumn. Compared to other icefish species with different geographical distributions, maximum sizes and lifestyles, P. maculata had the lowest growth performance and reproductive investment, primarily because of its smaller body size.

Ichthyoplankton assemblages in the south central Tyrrhenian Sea are not known in spite of this being an intensely fished area. There are two large canyons in this region: Dohrn, in the Gulf of Naples, and Cuma, at the south end of the Gulf of Gaeta. In this study, we provide the first description of summer ichthyoplankton assemblages in the vicinity of the two canyons and present the physical features and Lagrangian particle tracking analyses at the time of the sampling. We identified fish larvae of 19 families and fish eggs of 8 families. The most abundant species was Engraulis encrasicolus, which was found at densities comparable to other known spawning grounds of the western Mediterranean. Mesopelagic species, such as Gonostomatidae and Myctophidae, were also abundant, especially at the Cuma Canyon. The notochord and standard length of the E. encrasicolus larvae ranged from 2.06 to 10.47 mm and was significantly smaller at the Cuma stations than at the Dohrn stations, suggesting the presence of sub-populations with different spawning phenologies. The passive particle tracking analyses and the examination of currents confirmed distinct circulation features between the two sampled regions and in relation to depth and proximity to the canyon heads. These results uncover previously unknown rich assemblages of fish eggs and larvae and have conservation and management implications given the proximity of these canyons to a marine protected area and to an intensely fished continental shelf.

From 1 June 2010 in the Italian coastal waters of the Northern Adriatic Sea, trawl fishery within three nautical miles became banned. This activity was previously allowed for some species as an exception to legislation. In order to evaluate the consequences both on demersal resources and economic yields of the trawl which will oblige fishermen to trawl beyond three miles, a pilot study was performed. Twenty hauls comparing catch discard and income between hauls within and external to three nautical miles were performed. Results highlighted differences in catch composition both for landing and discard. Landing per unit of effort and discard per unit of effort did not differ in relation to distance from the coast, while income was higher for offshore hauls than inshore ones even if not significantly. Fishery management is a complex task, and the results of this study can contribute to the debate providing new insights into the consequences of the regulation on the trawling within three nautical miles. Considering the high amounts of discard, the habitat damages caused by otter trawling, the presence of juveniles in coastal waters and data regarding fishermen income, this study supports the actual European Community regulation on coastal trawling.

This paper presents a characterization of the fishing fleet operating in Campania, one of the twenty administrative Regions of Italy. An analysis of the contribution of the regional fleet to the national fishing capacity is also provided. The fleet is characterized​ according to its technical features (number of vessels, tonnage, engine power, length over all and fishing technique). The geographical distribution of Campanian vessels is also reported, thus highlighting the areas with the greatest importance for the fishery as well as those characterized by a predominant fishing technique. Also, the paper compares the results for the year 2018 with those of the previous years, thus offering an analysis of the trends followed by the Campanian fishing fleet in terms of the number of vessels, GT and kW. The results show that the regional fleet has lost one third of its size in nearly twenty years. Local fleet trends are set side by side with the evolution of the national, European and Mediterranean fleets. Finally, the study compares the evolution of capacity indicators with landing data of the fishery, showing that the capacity reduction caused by both management and market forces has not generated any tangible benefit to the targeted stocks and associated fisheries landings so far.

The adoption of parental care behaviours is the distinctive reproductive characteristic associated with the diversification and divergence of notothenioid fishes into an array of habitats in the subzero shelf and upper slope waters around Antarctica and sub-Antarctic environments. These include a variety of pre- and post-fertilization activities, including courtship behaviour and mate choice, linked to the development of sexually dimorphic traits, nest construction and egg guarding until hatch. Using published literature and new data, this review synthesizes and evaluates, in a phylogenetic context, information related to parental care, specifically sex-specific morphological adaptations, nest location and structure, sexual differences in egg guarding and post-spawning mortality, duration of egg incubation times and larval size at hatch. The existence of parental care in phylogenetically basal notothenioids is not documented and unlikely; however, the derived lineages of the Antarctic clade (cryonotothenioids), especially bathydraconids and channichthyids, clearly exhibit a trend towards larger egg size and reduced fecundity that are considered proxies for parental care behaviours. In addition, the reproductive strategies of cryonotothenioids exhibiting parental care show latitudinal patterns at intra- and inter-specific levels. Antarctic species spawn in spring-summer and have low fecundity, large egg size at spawning and large larvae at hatching. Sub-Antarctic species spawn in autumn-winter and have moderate to high fecundity, moderate egg size and larval size at hatching, whereas non-Antarctic species spawn in winter and possess high fecundity, small egg size at spawning and small larvae at hatching.

Parental care is a rather common reproductive strategy in fishes, particularly in species with low fecundity and large eggs as the Antarctic icefish (Channichthyidae). The infrequent use of underwater devices to record fish behaviour and the logistic limitations of operating in the Antarctic marine environment have prevented, so far, the collection of data about rare species. Integrating results from benthic trawling and underwater photographic images, we provide the first demographic and reproductive behavioural data for the channichthyid Neopagetopsis ionah, describing the nesting and parental care behaviour of a spawning population in the south-eastern Weddell Sea. The population sampled by the Agassiz trawl was dominated by females, and consisted of several post-spawning as well as a few mature females spread over a narrow size range. Based on otolith reading, the population included two cohorts estimated as four- and five-year-old fish. Following common trade-off between fecundity and egg size, females of N. ionah spawned few large eggs (733–1810 eggs/female, 4.9–6.5 mm in diameter). The nesting site was characterized by fine sediments with sparse gravel and the accompanying benthic invertebrate community showed low densities and was relatively poor. A total of 93 nests were counted along the video transect, most of them with a single guarding male or left unattended. Fish remains or whole dead specimens were frequently observed in the proximity of the nest. This observation represents the first record of post-spawning mortality associated with parental care which has never been documented before in Antarctic fishes.

The Mediterranean Sea has a long-lasting history of fishery exploitation that, together with other anthropogenic impacts, has led to declines in several marine organisms. In particular, elasmobranch populations have been severely impacted, with drastic decreases in abundance and species diversity. Based on their experience, fishers can provide information on marine species occurrence, abundance and behavioural traits on a long-term scale, therefore contributing to research on the poorly studied biological aspects of elusive or rare elasmobranch species. In this study, for the first time, the use of the Local Ecological Knowledge (LEK) of fishers was applied to study the behavioural traits of sharks, rays and skates in 12 FAO-GFCM geographical sub-areas (GSAs) of the Mediterranean Sea. This study found both new insight and proved the reliability of LEK-based catch seasonality, reflecting seasonal movements, by comparing LEK-based findings and available literature on five elasmobranch taxa (Mustelus spp., Squalus acanthias, Raja spp., Myliobatis aquila and Scyliorhinus stellaris) in the Adriatic Sea and 7 taxa (Mustelus spp., Raja spp., Prionace glauca, Scyliorhinus canicula, Torpedo spp., Pteroplatytrygon violacea and Isurus oxyrinchus) in the remaining Mediterranean GSAs. In addition, LEK provided new insights into a novel comprehensive representation of species aggregations (Mustelus spp., S. acanthias, M. aquila and S. canicula) in the sampled GSAs and supplied the first descriptions of the size, number of individuals and sex composition of the aggregations. When the limits and shortcomings of LEK-based research are considered, this methodology can be a complementary and cost-effective tool used to study elasmobranchs in either a data-poor scenario or a scenario in which a baseline is missing. LEK can also be useful for the evaluation and inclusion of fishers’ perceptions on bottom-up management and to provide important evidence for conservation plans.

The species of the genus Chionodraco (Notothenioidei) are the most abundant icefish on the continental shelf of the Weddell Sea. While previous studies indicated that only Chionodraco hamatus and Chionodraco myersi inhabit the Weddell Sea, the third Chionodraco species, Chionodraco rastrospinosus, was recently sampled in the area. As C. rastrospinosus is supposed to be found only at the Antarctic Peninsula and Scotia Arc, this study aimed at confirming the species classification of C. rastrospinosus by molecular methods and identifying its putative source population. Given the documented evidence of introgression among the three species, we tested whether the newly found C. rastrospinosus shared any genetic variability with the other Chionodraco species. To explain the pattern of distribution of the Chionodraco species, we aimed at estimating the hydrodynamic connectivity between the Antarctic Peninsula and the Weddell Sea.

The bigeye notothen, Trematomus tokarevi , is a rare nototheniid fish with a putative circum-Antarctic distribution. Due to its prevalent deep water occurrence, this species is rarely caught and its biology poorly known. In addition, this species has been often misidentified with Trematomus nicolai , a morphologically similar species with a partially overlapping distribution. The odd catch of a few specimens of T. tokarevi in the southern Weddell Sea enabled us to provide for the first time preliminary data on reproductive traits and individual age of this species. Fish sample consisted of five females, collected in the austral summer north east of the Filchner Trough at about 750 m depth. Based on histological analyses of gonads, smaller females were in early developing phase, whilst larger ones were regressing, suggesting a summer spawning season, as reported elsewhere. The analysis of growth rings pattern of sagittal otoliths allowed to estimate the individual age, which ranged between 4 and 10 years. In conclusion, this species exhibits most of the common biological traits described in other trematomids, although with some peculiarities, showing at the same time low fecundity and small egg size at spawning.

Despite their wide distribution around the Antarctic continent, the life strategies of the long-fingered icefish Cryodraco antarcticus have been rarely investigated and are not well understood. The aim of this paper was to provide more insights on the demographic characteristics of the population living off the South Shetland Islands, focusing attention on key biological traits such as age and growth and the reproductive cycle. Individual age and reproductive status were assessed through the microstructural analyses of sagittal otoliths and histological analysis of gonads, respectively. The sex-balanced sampled population consisted of juvenile and adult fishes covering a wide size range. Both sexes had positive allometric growth, although males exhibited smaller maximum size and lower body condition than females. Fish longevity was comparable between sexes, being 16 and 18 years in males and females, respectively. Applying the von Bertalanffy growth model to length-at-age estimates, males consistently reached lower maximum asymptotic size at a faster rate than females. Based on the gametogenic process, the spawning period was inferred to occur from late summer to early autumn. As commonly found in icefishes, females devoted a great investment to reproduction as gonadosomatic index, egg size, and fecundity. A single female (62 cm TL) spawned about 7730 eggs as large as 3–4 mm. Considering also the results of previous studies conducted in other areas, this species is characterized by a long-lasting pelagic juvenile phase and adults share similar life strategies across the range of their spatial distribution, suggesting the possibility of a single panmictic circum-Antarctic population.