Data-mining social media platforms highlights conservation action for the Mediterranean Critically Endangered blue shark Prionace glauca

Abstract The Mediterranean Sea represents an area of elevated risk of extinction for sharks, where data deficiency is a pervasive problem. To compensate for such a paucity of information, this study investigated the use of social media content as a complementary approach to evaluate the distribution and habitat use of the Critically Endangered blue shark Prionace glauca in coastal waters, as well as public perceptions of the sharks. Through social media data mining a total of 146 records, comprising 158 individual blue sharks approaching Italian coastal waters, have been recorded from 2011 to 2020. This study revealed that, over the past decade, blue sharks regularly visited Italian coastal habitats for extended periods of time. Differences in the temporal distribution of blue sharks by sex and size appear to be linked to reproductive activity. The higher number of adult females approaching the shore in spring and the increase in young‐of‐the‐year (YOY) sightings in the following months possibly indicate parturition in coastal waters. Spatial analyses also showed that certain Italian coastal areas, such as those in Calabria and Puglia, were preferred coastal habitats for this species. Results also indicate that social media platforms can be considered an ever‐growing source of data on wildlife, which can shed light on the occurrence and distribution of endangered shark species in poorly known habitats. Furthermore, social media platforms should be used for awareness campaigns to educate the public, as this study showed that negative reactions to shark encounters remain widespread

First documented record of the leatherback turtle (Dermochelys coriacea) from Djibouti waters

AbstractA subadult leatherback turtle was documented in the Gulf of Goubet (Djibouti) during a research expedition. This sighting confirms for the first time previous anecdotal observations of the occurrence of the leatherback turtle, Dermochelys coriacea (Vandelli, 1761), in Djibouti waters. Coupled with observations from fishers, this finding underlines the urgent need to carry out research programs to evaluate the species habitat use within Djibouti waters, and to review the species distribution in the Gulf of Aden. Although marine turtles are protected in Djibouti, illegal harvest and entanglement in fishing gear pose a threat to their survival, and conservation measures should be implemented

Annual Recurrence of the Critically Endangered Bowmouth Guitarfish (Rhina ancylostomus) in Djibouti Waters

One of the least understood and most threatened groups of elasmobranchs is the Rhinopristiformes, the guitarfishes, wedgefishes, and sawfishes. Numbering more than 60 species, this order includes a high percentage of Critically Endangered and Endangered species, as designated by the International Union for the Conservation of Nature. There is a dearth of data on these species due to sightings being infrequent and unpredictable. Globally, Rhinopristiformes are both directly targeted for their meat and large fins and are caught as bycatch in their near-shore habitats. We report here a consistent and predictable long-term presence of the Critically Endangered bowmouth guitarfish (Rhina ancylostomus) in the Gulf of Tadjoura, Djibouti. This species has been reliably encountered during diving and whale shark research activities (November-February) over seven seasons, indicating long-term site fidelity of R. ancylostomus within the area. Currently receiving minimal legal protection and facing unknown fishing pressures and ecological risks, these animals and their habitat should be prioritized for research and conservation

Zooplankton as an indicator of the status of contamination of the Mediterranean Sea and temporal trends

Zooplankton has been intensively used as bioindicators of water pollution at global level, however, only few comprehensive studies have been conducted from the Mediterranean Sea and manly dated back to the 1970s. To redress the urgent need for updated data, this study provides information on the presence and levels of contaminants in zooplankton from the Tyrrhenian Sea. Although banned, both PCBs (46.9 +/- 37.2 ng g-1) and DDT (8.9 +/- 10.7 ng g-1) are still present and widespread, but their contamination appears to be a local problem and to be declining over the past 50 years. Zooplankton accumulates high levels of certain TEs, including Zn (400 +/- 388 ppm) and Pb (35.3 +/- 45.5 ppm), but shows intermediate concentrations of other TEs, including Cd (1.6 +/- 0.9 ppm) and Hg (0.1 +/- 0.1 ppm), comparing with both strongly polluted and more pristine marine habitats, which may reflect a general improvement

Playing “hide and seek” with the Mediterranean monk seal: a citizen science dataset reveals its distribution from molecular traces (eDNA)

Animal conservation relies on assessing the distribution and habitat use of species, but for endangered/elusive animals this can prove difficult. The Monk Seal, Monachus monachus, is one of the world's most endangered species of pinniped, and the only one endemic to the Mediterranean Sea. During recent decades, direct observations have been few and scattered, making it difficult to determine its distribution away from the Aegean Sea (core distribution area of the post-decline relict population). This study relies on environmental DNA (eDNA) analysis to detect the presence of the Monk Seal in 135 samples collected in 120 locations of the central/western Mediterranean Sea, spanning about 1500 km longitudinally and 1000 km latitudinally. A recently described species-specific qPCR assay was used on marine-water samples, mostly collected during 2021 by a Citizen Science (CS) project. Positive detections occurred throughout the longitudinal range, including the westernmost surveyed area (Balearic archipelago). The distribution of the positive detections indicated six “hotspots”, mostly overlapping with historical Monk Seal sites, suggesting that habitat-specific characteristics play a fundamental role. We applied single-season occupancy models to correct for detection probability and to assess the importance of site-specific characteristics. The distance from small islets and protected (or access-restricted) areas was correlated negatively with the detection probability. This novel molecular approach, applied here for the first time in an extensive CS study, proved its potential as a tool for monitoring the distribution of this endangered/elusive species

Identifying priority sites for whale shark ship collision management globally

The expansion of the world's merchant fleet poses a great threat to the ocean's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable species. The Endangered whale shark (Rhincodon typus) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These "constellation" sites are of significant ecological, socio-economic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world (>50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species

Whale shark foraging on baitfish off Djibouti

In the Gulf of Tadjoura, Republic of Djibouti, whale sharks (Rhincodon typus Smith, 1828) are known to feed on a wide variety of zooplankton organisms. However, for the first time in this area, seven juvenile whale sharks were filmed feeding on a school of baitfish (anchovies). During the event, zooplankton samples were collected and biomass was calculated. Results support the hypothesis that when dense patches of zooplankton are not available in the Gulf of Tadjoura, whale sharks remain in the area and feed on alternative energy-rich prey, such as baitfish, to meet their energetic demands

To what extent are filter feeder elasmobranchs exposed to marine pollution? A systematic review

: Filter feeding elasmobranchs may be considered as biological indicators of marine pollution, despite most of these species are under some degree of extinction risk. Among threats to this taxonomic group, marine pollution might represent an additional concern for their survival. In this review, a comprehensive systematic search of scientific literature on pollutants in filter feeding elasmobranchs was conducted to evaluate the bioaccumulation patterns, and risk for human consumers. We found that, despite an increasing trend in the number of published studies, the geographical coverage is still very limited and most of the studies focused solely on trace elements (70.8%). Among sharks, Rhincodon typus was the most represented species (66.7%), while Mobula mobular the most studied ray species (41.7%). Comparing the levels of pollutants in filter feeders between ocean basins, this review highlighted that Hg, As and Cd levels are mostly higher in those areas affected by both strong natural and anthropogenic source of emissions, such as the Indian Ocean. With regards to OCs, ΣPCB levels in muscle of C. maximus were between 4.3 and 50.5 μg kg-1 ww, highlighting a persistent contamination of PCB in the Mediterranean Sea. Some species exceeded the maximum allowable limits for foodstuff consumption for As, Cd and Pb. A total of 77.8% of the analyzed species exceeded the Environmental Quality Standards for Hg, while they were always below the EQSbiota for HCB, PBDEs, PFOS and DDT. Given their feeding mechanism that continuously samples the marine environment, further investigations are urgently needed to determine not only the extent of contaminant exposure in different hotspot locations but also the risks posed to the elasmobranch health

The ecology of the whale shark in Djibouti

Within the Gulf of Aden, Djibouti is an important site where whale sharks (Rhincodon typus Smith 1828) aggregate seasonally; however, up to now, only few studies have been carried out in the area (Rowat et al. in Environ Biol Fishes, 2007. https://doi.org/10.1007/s10641-006-9148-7; Mar Freshw Res, 2011. https://doi.org/10.1071/MF10135; Rezzolla and Storai in Cybium 34:195\u2013206, 2010). From 2015 to 2018, whale shark photo-id, skin biopsies, and zooplankton samples were collected to investigate the ecology of this species in Djibouti. Of the 190 photo-identified individuals, the majority were juvenile males, confirming a significant male-based aggregation (X2 = 65, df = 1, p < 0.0001). Within each season, the maximum number of times an individual was re-sighted was 11, while the inter-annual re-sighting rates varied between 11 and 32%. Animals were feeding on surface zooplankton, consisting primarily of copepods (85%); however, Chaetognatha and Ctenophora appeared to be important taxa as well, since the areas most visited were also those with higher concentration of these organisms. Feeding zooplankton patches had a mean biomass of 42.2 \ub1 31.9 mg m 123, almost 1.5 higher than control stations, indicating that the abundance of this species was positively related to food availability. Furthermore, whale sharks exhibited a clear temporal distribution associated with the variation in zooplankton biomass due to the monsoon winds. Sharks aggregated in October\u2013February, with a peak in sightings in November, and dispersed outside the upwelling season. \u3b413C values suggested that whale sharks might migrate to other habitats or shift their activities to deeper areas outside the aggregation phase. Little intra-specific variation in \u3b415N and \u3b413C was found between animals, suggesting a similar habitat use

Evaluation of a low-cost, non-invasive survey technique to assess the relative abundance, diversity and behaviour of sharks on Sudanese reefs (Southern Red Sea)

A low-cost and non-invasive survey technique focused on pelagic sharks was evaluated during an ecotourism cruise on two Sudanese reefs, Angarosh and Sha'ab Rumi, in the Southern Red Sea. The research technology was based on a set of small, underwater video recording cameras and a pair of laser pointers. Video footage provided insight into shark biodiversity on the two reefs, detecting five species, Alopias vulpinus, Sphyrna lewini, Triaenodon obesus, Carcharhinus amblyrhynchos and Galeocerdo cuvier, during 15.8 h of video recording. These recordings also provided preliminary information on aggregations of S. lewini. The laser pointers were used to measure the size of sharks, providing seven total length (TL) measurements for S. lewini (N = 2) and C. amblyrhynchos (N = 5), confirming the possibility of easily obtaining size parameters using this tool. These low-cost and user-friendly instruments provide ecotourism divers with an opportunity to become involved in marine research projects. © Marine Biological Association of the United Kingdom 2014