Abstract
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.
Highlights
The aspects on which we focused were growth parameters, feeding habits, and size at sexual maturity in specimens of G. melastomus from the southern Tyrrhenian Sea
For the entire sample, Results obtained with the analysis of covariance (ANCOVA) test showed that females were heavier than males (p-value the total length ranged from 14.5 to 52 cm (SD = 9.4), and the weight from 9.5 to 538 g
Further studies are needed to better understand the biology and ecology of this species in the Mediterranean Sea, our study provided new data on several biological and ecological aspects of G. melastomus in the southern Tyrrhenian Sea and contributed to filling some of the gaps in the literature
Summary
Elasmobranchs are a key group for the smooth functioning of marine ecosystems, as they regulate prey populations and the ecological dynamics among the different habitats they move between [1,2,3,4]. Skates, and rays are both top predators and mesopredators in most marine environments, but despite their importance, elasmobranchs are seriously threatened by fishing activities worldwide. Their vulnerability to fishing activities, both directly for human consumption (meat and fins) and as by-catch in several fisheries, is related to their reproductive cycle, characterized by low fecundity and delayed age at maturity [5,6]. More than half of the Mediterranean elasmobranchs are regarded as threatened (included in the IUCN red list) [7], including “deep-water species”
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