Data on the biology and ecology of Galeus melastomus are old/absent for the Southern Tyrrhenian Sea, despite there being numerous studies in the wider area. A total of 127 specimens of G. melastomus from the southern Tyrrhenian Sea, collected in 2018–2019 using trawling nets, were analyzed to investigate size at sexual maturity, sex ratio, length–weight relationships, and feeding habits. To our best knowledge, this is the first time in which all these features were investigated in the Southern Tyrrhenian Sea for G. melastomus. The stomach content analysis showed that G. melastomus had intermediate feeding habits, preying on a great variety of species, especially Cephalopoda, Osteichthyes, and Crustacea. The Levin’s index value (Bi) was 0.53. Sex ratio was 0.92:1, with females slightly more abundant and bigger than males. The results also showed a decrease (33.7 cm for females, 31.1 cm for males) in length at 50% maturity (L₅₀). This could be a result of anthropogenic stressors, such as overfishing and/or and environmental changes, which can induce physiological responses in several species. Our results highlighted the differences related to sexual maturity, growth, and feeding habits of the blackmouth catshark in the studied area, providing reference data to allow comparison with future studies on this species adaptations to this and other deep-sea areas in the Mediterranean Sea.

The progressive increase of marine macro-litter on the bottom of the Mediterranean Sea is an urgent problem that needs accurate information and guidance to identify those areas most at risk of accumulation. In the absence of dedicated monitoring programs, an important source of opportunistic data is fishery-independent monitoring campaigns of demersal resources. These data have long been used but not yet extensively. In this paper, MEDiterranean International Trawl Survey (MEDITS) data was supplemented with 18 layers of information related to major environmental (e.g. depth, sea water and wind velocity, sea waves) and anthropogenic (e.g. river inputs, shipping lanes, urban areas and ports, fishing effort) forcings that influence seafloor macro-litter distribution. The Random Forest (RF), a machine learning approach, was applied to: i) model the distribution of several litter categories at a high spatial resolution (i.e. 1 km²); ii) identify major accumulation hot spots and their temporal trends. Results indicate that RF is a very effective approach to model the distribution of marine macro-litter and provides a consistent picture of the heterogeneous distribution of different macro-litter categories. The most critical situation in the study area was observed in the north-eastern part of the western basin. In addition, the combined analysis of weight and density data identified a tendency for lighter items to accumulate in areas (such as the northern part of the Tyrrhenian Sea) with more stagnant currents. This approach, based on georeferenced information widely available in public databases, seems a natural candidate to be applied in other basins as a support and complement tool to field monitoring activities and strategies for protection and remediation of the most impacted areas.

We reviewed literature on the diet of the Galeus melastomus Rafinesque, 1810, from the Mediterranean Sea. Specific keywords (“Galeus melastomus diet”, “feeding habits”, “trophic position”, “biology”, “deep environment adaptation”) in the principal data sources, such as Web of Science, PubMed, and Google Scholar were used. Seventeen studies conducted on the diet and trophic position of G. melastomus have been considered for Mediterranean Sea regions. The feeding habits have been analyzed in many areas of the western basin; instead, for the Tyrrhenian, Adriatic, and central Mediterranean Seas, information is outdated and fragmentary. In all investigated sub areas, the data showed that G. melastomus is an opportunistic demersal supra benthic predator, benthic feeder, and scavenger, that adapts its diet to the seasonal and geographical fluctuations of the prey availability. It occupies a generalist niche showing individual specialization. In all reviewed Mediterranean sub areas, the most important prey groups were crustaceans, cephalopods, and teleost fishes. Taxa percentage in its diet composition can vary depending on different habitats with ontogenetic development of individuals, depth (that is correlated with the ontogenetic development), seasonal availability, and distribution of different prey groups. Widening knowledge of G. melastomus feeding habits is a fundamental tool for better understand meso and bathy-pelagic ecosystems.

The present paper aims to investigate the ecological role of Merluccius merluccius, Linnaeus, 1758, in southern and central Tyrrhenian Sea (GSA 10, Resolution GFCM/33/2009/2 General Fisheries Commission for the Mediterranean), analyzing ontogenetic diet shifts, geographical variations on prey composition, and feeding habits. A total of 734 hake specimens ranging in size between 6 cm and 73 cm (Total Length, TL) were collected in 2018. In order to evaluate ontogenetic shifts in prey composition, samples were divided into five size classes and for each class the quantitative feeding indices have been calculated. The statistical analysis, based on index of relative importance percentage (%IRI), resulted in three trophic groups. The most abundant prey found in the immature hake specimens (size class I) were the Euphausiids, Stylocheiron longicorne and Mysidacea, while for samples with a total length over 10.5 cm were crustaceans and fish. Engraulis encrasicolus was the most abundant fish prey identified, followed by Boops boops and Myctophids. The high presence of Euphausiids, Mysids, Myctophidae, and Sternoptychidae in classes I, II, II, and IV (6–23 cm) showed the relevant role of mesopelagic fauna in hake diets, with an essential organic matter and energy flow from the mesopelagic to the epipelagic environment. Additionally, decapod crustaceans were found in the stomach contents of hakes belonging to class V (with size over 36 cm TL), which is notable considering that our study area includes an important decapod crustacean fishing area.

Merluccius merluccius is one of the most important Mediterranean benthopelagic predators. It represents a key species for the ecosystem’s functioning due to its fundamental role in the energy transferal between different domains and depth strata. The aim of this study was to explore the feeding habits of European hakes in the southern and central Mediterranean Sea, and also to analyze timescale variations and ontogenetic shift in five size length classes. A total of 411 stomachs collected from 2018 to 2020 were analyzed to assess diet and feeding habits. Results confirmed hakes’ role as a generalist benthopelagic predator, preying both in the suprabenthic layer and in the entire water column. Concerning the ontogenetic diet shift, juvenile hakes prefer zooplanktonic prey, while larger hakes have a diet mainly based on teleosts and decapods. The variations in diet composition between years, characterized by a fluctuation of cephalopods, bioluminescent teleost species and mesopelagic crustaceans, have highlighted the ability of European hake to model its diet to the geographical and prey availability. These features make analysis of the diet of M. merluccius essential to understanding the trophic dynamic existing in bentho-meso-pelagic environments, to improve ecosystem conservation in accordance with ecosystem-based fishery management.