9/27/2023 0 Comments Uninstall deeptrawl![]() These problems are particularly severe for species characterized by low abundances or considered rare, for which only scattered observations and fragmented knowledge are available, thus resulting of extreme importance. ![]() In addition, the problem is compounded by the lack of nomenclature stability and taxonomic resolution, due to the taxonomic issues typical of the cartilaginous species, combined to the ongoing changes in species occurrence in the different parts of the basin. As a twofold consequence, on the one hand, these species are marketed grouped under generic names, raising additional difficulties in collecting landings information and, on the other, they often take second place in official data collection programs. Species with low commercial value, indeed, are not directly targeted by commercial fishery, being instead part of its by-catch. The underlying causes of this data scarcity are linked to several concomitant factors, such as low commercial value and taxonomic uncertainty. Furthermore, a large number of species (about 20%) are listed as Data Deficient, testifying that knowledge on them is insufficient to make any refined assessment, creating uncertainty on their extinction rates at a global level and excluding them from priority species list at a regional scale. Moreover, some of these assessments appear to be quite old and need to be updated. The International Union for the Conservation of Nature (IUCN) estimates that at least 53% of the 88 species currently inhabiting the basin are Vulnerable, Endangered or Critically Endangered. This led to a rapid decrease in abundance of many Mediterranean populations of sharks and batoids observed during the last 50 years and, in the worst cases, to some local extinctions. At the same time, due to their k-selected life-history traits, cartilaginous fish are particularly vulnerable to overfishing, habitat deterioration and to the modifications in the biological communities’ composition, which are also linked to biodiversity loss and to the introduction of alien species, in a rapidly changing scenario. Among these, cartilaginous fishes such as sharks, batoids (skates and rays) and chimaeras are certainly some of the most iconic species for the majority of public opinion, mainly due to their fundamental ecological role as top predators. Even though the Mediterranean basin represents only 1% of the global oceans, it is estimated that it hosts up to the 18% of the world’s macroscopic marine species, about 30% of which are endemic. In this context, the Mediterranean Sea is considered, at the same time, a biodiversity hotspot and one of the most threatened marine areas in the world. Due to this high resource availability, the human pressure on marine ecosystems is constantly rising, thus negatively impacting their biodiversity. Marine ecosystems represent Earth’s largest biodiversity reservoirs, providing a wide range of contributions to human well-being, which collectively go under the name of Marine Ecosystem Services. On the basis of the stomach content analysis, it was possible to identify five different predator groups. licha, which appeared to be capable of reproducing earlier than what was previously hypothesized, representing very valuable information for a better understanding of these rare species populations status and, eventually, their conservation. In addition, the present study updates the sizes of first maturity of C. circularis which were both found capable of becoming older than ten years. Particularly, the present paper provides for the first time the age estimation of D. In this regard, this paper aims at providing new information on the life-history traits, such as age, maturity, reproductive period, in addition to diet characteristics of eleven rare cartilaginous fish inhabiting the Central-Western Mediterranean Sea belonging to the orders Chimaeriformes ( Chimaera monstrosa), Hexanchiformes ( Heptranchias perlo and Hexanchus griseus), Myliobatiformes ( Aetomylaeus bovinus and Myliobatis aquila), Rajiformes ( Dipturus nidarosiensis and Leucoraja circularis), Squaliformes ( Centrophorus uyato, Dalatias licha and Oxynotus centrina) and Torpediniformes ( Tetronarce nobiliana), useful for their assessment and for future management actions. ![]() Nevertheless, effective management plans for cartilaginous fish are still missing, due to the lack of knowledge on their abundance, distribution or even life-history. Cartilaginous fish are commonly recognized as key species in marine ecosystems for their fundamental ecological role as top predators.
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