The Mediterranean Sea is a hotspot for shark conservation. A decline in large pelagic shark populations has been observed in this vast region over the last 50 years and a lack of data on the local ...population status of various species has been pointed out. Throughout history, the relation between people and sharks has been revolving around a mixture of mystery, fear, and attraction. Recently, however, a remunerative ecotourism industry has been growing in areas of shark aggregation globally. This growth has been accompanied by the establishment of a citizen science (CS) movement aimed to engage and recruit ecotourists in data collection for shark research. Several CS projects have generated interesting results in terms of scientific findings and public engagement. In the Mediterranean Sea, shark aggregations are not as relevant to support locally-focused CS actions on shark diving sites as in other parts of the world. However, a series of other initiatives are taking place and CS could offer an excellent opportunity for shark conservation in the Mediterranean Sea. The dramatic decline of shark populations shown in the region calls for alternative ways to collect data on species distributions and abundance. Obtaining such data to set proper conservation and management plans for sharks in the Mediterranean Sea will be possible if existing CS initiatives collaborate and coordinate, and CS is widely acknowledged and deployed as a valuable tool for public education, engagement, and scientific discovery. After providing an overview of multiple facets of the relationship between humans and sharks, we focus on the possibility of exploiting new technologies and attitudes toward sharks among some groups of ocean users to boost participatory research. CS is a great opportunity for shark science, especially for areas such as the Mediterranean Sea and for large pelagic sharks whose populations are highly impacted.
Species diversity assessments are an important step to evaluate the conservation status of a community, both in marine and terrestrial ecosystems. These assessments are pivotal if related to both, ...the constant increase of human pressure on ecosystems and the anthropogenic climate change occurring nowadays. Sharks and rays are globally threatened, and the situation is particularly alarming in the Mediterranean Sea where more than 50% of species are listed at risk of extinction by the International Union for Conservation of Nature (IUCN). In this paper, we revise and discuss the chondrichthyan species richness of the Mediterranean and the Black Sea. Through an accurate review of published taxonomic studies, historical data on species occurrence, analyses of scientific survey data and biodiversity databases and other scientific papers, we produced a revised list of species whose presence in the Mediterranean Sea is confirmed or highly probable and discussed on current taxonomic and occurrence disputes on the species that are instead rarer or claimed to be locally extinct. We listed a total of 88 species, representing 30 families and 48 genera that are currently present in the Mediterranean and the Black Sea. This number includes 48 shark species, 38 batoids, and 2 chimaeras. The review represents a reference for future conservation assessments of cartilaginous fish in the region and a guide for decision-makers when promoting the sustainable exploitation of fisheries resource within an ecosystem-based framework. This paper can help to set a baseline of the Mediterranean species and thus resolve some uncertainties regarding their conservation status, explaining the reasons for their prolonged absence in the reports. Indeed, failure to record over time may not be due to grubbing up, but because after careful review this species was not really part of the Mediterranean fauna.
In the last 50 yr, shark populations showed steep declines in the Mediterranean Sea. The IUCN lists most Mediterranean species as threatened (55%), while considering 27.5% of them Data Deficient. ...Here, sharks are currently one of the rarest and more elusive groups of animals, and data from fisheries and scientific monitoring still insufficiently support robust abundance and distribution assessments. New technologies can fill this data gap by linking people and scientists through new monitoring strategies. SharkPulse, an international collaborative project, aims at creating a large world database of shark occurrence records by mining images on the web, social networks, and private archives. Here we analyzed 1186 sharkPulse records from the Mediterranean Sea. We collected records to characterize spatio-temporal patterns on 37 species, highlighting distribution changes for 5, and, by using generalized linear models, estimating trends in sighting for the most abundant species. With 273 records,
Hexanchus griseus
had the most sighting records since the beginning of the series. We identified pupping areas and aggregation sites for immature
Prionace glauca
and
Isurus oxyrinchu
s
; pinpointed strongholds of the Critically Endangered
Squatina squatina
to focus conservation efforts; and identified broader than previously reported regional distribution ranges for
Alopias superciliosus
,
Dalatias licha
,
Heptranchias perlo
,
H. griseus
,
Oxynotus centrina
, and
P. glauca
. We confirmed that fishing is still the major threat for Mediterranean sharks and call for a greater effort in controlling the emerging patterns with efficient conservation effort indexes. If properly standardized, opportunistic data can efficiently and cost-effectively advance our understanding of shark abundance, distribution, and conservation status.
The Aegean region of Greece hosts a series of crustal-scale extensional detachment systems that have accommodated the southward retreating Hellenic subduction zone. Extension has overprinted and ...dissected the Alpine nappe pile and locally exhumed Cordilleran-type metamorphic core complexes. On the island of Paros, a low-angle extensional detachment fault separates metamorphic footwall rocks from an unmetamorphosed sedimentary succession of the hanging wall. Basement orthogneisses were extensionally sheared in the footwall of the detachment until after 16Ma (zircon U–Pb age of a slightly deformed granite), but pervasive ductile deformation had ceased by 7Ma (zircon U–Pb age of an undeformed rhyolite dike that intrudes gneisses). Apatite and zircon (U–Th)/He ages from the gneisses confirm a period of cooling at rates >100°C/Ma from 16 to 7Ma. In the upper-plate, the basal sedimentary unit yields reset detrital apatite (U–Th)/He (DAHe) ages from 17 to 7Ma and detrital zircon (U–Th)/He (DZHe) ages ranging from 270 to 18Ma. DAHe ages from the stratigraphically higher fanglomerate units are reset to 10–7Ma. The DZHe data have a primary thermal signature of 12–7Ma, but preserve ages up to 113Ma. The uppermost conglomerates exhibit completely reset DAHe ages of 15–9Ma and reset DZHe ages from 10 to 8Ma, with DZHe ages up to 104Ma. Reset DAHe ages indicate late exposure of the footwall and constrain the depositional age of most sedimentary rocks on Paros to be from 14 to 7Ma. Unreset DZHe ages preserve thermal signatures from the major Mesozoic–Tertiary tectonic events in the Aegean Region: 1 Cretaceous Pelagonian-type metamorphism; 2 Eocene peak HP metamorphism; and 3 Miocene Barrovian overprinting. Preservation of these signatures indicates long-term upper-plate recycling prior to syn-extensional deposition. The Paros supradetachment basin represents a classic inverted unroofing sequence deposited during progressive core complex exhumation in the Middle to Late Miocene.
► New zircon U–Pb and (U–Th)/He data from the core complex on Paros, Greece ► Footwall underwent ductile shearing after 16Ma and brittle shearing after 7Ma. ► The Paros footwall cooled at rates >100°C/Ma for a short period between 16 and 7Ma. ► Detrital apatite (U–Th)/He data from Paros constrain deposition to be 14–7Ma. ► Detrital zircon (U–Th)/He data from Paros record episodes of regional tectonism.
A major limitation in the accuracy of zircon (U–Th)/He thermochronometry (ZHe) is the alpha-ejection correction. The standard alpha-ejection correction (FT) assumes a homogeneous U–Th distribution in ...the host crystal. Here, two approaches are used to address parent nuclide heterogeneity often observed in natural zircons: 1) a new methodology where offending zonation is mechanically removed, and 2) custom alpha-ejection corrections informed by a LA-ICP-MS depth-profile (FZAC). We present an empirical test of these methodologies on a suite of bedrock zircons from Variscan orthogneisses of the central Aegean, which display marked parent nuclide zonation, which has impacted the ability to obtain accurate and precise thermochronometric data. During the progressive mechanical abrasion of enriched U, Th, and He zones, the change in grain diameter exhibits a parabolic relationship with respect to the apparent age, where the youngest age should represent the true age of the sample. The abrasion-corrected weighted mean age for sample 08PA01 is 8.8±0.7Ma (FT=1), a “too young” age possibly the result of parent nuclide enriched cores. The findings also show that using FZAC instead of FT may change single sample ZHe aliquots up to ~29%. Using FZAC increases the weighted mean age ~17% for sample 08PA01, from 9.2±0.7Ma (FT) to 10.8±0.9Ma (FZAC), and ~6% for sample 08PA71, from 10.9±0.8 (FT) Ma to 11.5±0.9Ma (FZAC). In this case, the FZAC correction improves the overall accuracy of the ZHe data, but does not impact the problem of over-dispersed ages, suggesting they may be separate issues. The increase in ZHe age brings the dataset into agreement with previous thermochronometric studies, indicating that cooling of the Paros footwall below 180°C may have occurred earlier than hitherto thought.
•New methods for improving the accuracy of zircon (U–Th)/He.•Modeled 3D α-ejection corrections from laser ablation-derived nuclide concentration.•Heterogeneous zircons from an Aegean core complex are used to demonstrate method.•Further refinement needed to reduce overdispersion of ages.
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