Tethys Research Institute

A solitary common bottlenose dolphin Tursiops truncatus entered the Venetian Lagoon and was monitored between June–December 2025. After roaming the lagoon for three months, it settled in Venice, with a preference for waters adjacent to San Marco Square – one of the world’s busiest tourist destinations – where it was consistently observed feeding on mullet (Mugilidae). The Venetian Lagoon was historically part of the range of Adriatic dolphins, but such records have been rare since the 1970s. The ‘dolphin of Venice’ soon became a celebrity, resulting in people attempting to feed, touch and interact with the animal, as well as guided tours and erratic approaches by boats. Such inappropriate behaviour by humans increased disturbance, and the risk of propeller/boat strikes and habituation to human proximity. Following evidence of disturbance and lesions, in November 2025 an attempt was made to drive the dolphin away from the high-risk waters of the San Marco Basin using boats and acoustic deterrents. However, the dolphin immediately returned. Here, we report on the monitoring efforts and actions undertaken, review the relevant regulations, and discuss the options of 1) acoustic deterrence, 2) capture/removal, and 3) tolerance combined with best management practice. We argue that the occurrence of such a charismatic animal could serve as a model for human-wildlife coexistence in urban environments, demanding compliance with existing laws, area-specific measures, appropriate implementation and patrolling, resolute deterrence of inappropriate human behaviour, continued monitoring, and efforts to promote the type of social change that leads to widespread appreciation of, and respect for, wildlife.

The comparability of methods applied to environmental DNA (eDNA) samples across laboratories remains a significant challenge for biodiversity monitoring on a global scale. Performance differences between protocols can jeopardize effective conservation strategies across regions and focal species. To address potential discrepancies amongst four international partners within a collaborative eDNA initiative, an inter-laboratory comparison (i.e., ring test) was conducted to compare efficiencies of established DNA extraction methodologies based on 39 eDNA samples. Each laboratory contributed eight to eleven samples collected throughout the North-East Atlantic and the Mediterranean Sea near sperm whales, porbeagle sharks, basking sharks, bottlenose dolphins and common dolphins. After lysis, aliquots were exchanged between laboratories before subsequent DNA extraction using each facility’s preferred method. Extracts were returned to the lysates’ respective laboratories of origin for measurements of total DNA concentration, as well as quantitative PCR using three novel species-specific assays for marine megafauna. Our findings revealed similar concentrations of total DNA, yet a significant reduction in extraction performance for targeted qPCR reactions by one laboratory, who has therefore modified their extraction method to be used for the remainder of this project. Overall, detection success differed based on the target taxa with sharks being less often detected (and at lower concentrations) than marine mammals. Significant interaction effects were found between combinations of laboratories and species, suggesting a link between extraction protocols and variable environmental conditions. Our study serves as a foundational step towards establishing reproducible practices that are crucial for the success of multinational eDNA projects to enable comparable results.

Monitoring cetaceans is essential for evaluating ecosystem health and informing the establishment of marine protected areas. Conventional cetacean monitoring techniques, such as photo-identification, acoustic surveys, and satellite tagging, are often resource-intensive, costly, and sometimes intrusive. Environmental DNA (eDNA)-based methods have emerged as non-invasive, cost-efficient complements based on the analysis of genetic material shed into the environment. However, eDNA research is still evolving, with ongoing efforts to optimize field sampling and laboratory protocols. Building on the challenges of conventional monitoring methods, this study sought to refine eDNA sampling parameters to offer a more efficient and scalable approach for cetacean research, leveraging citizen science platforms. From June to October 2023, eDNA samples were collected across three regions in the Northeast Atlantic Ocean and Mediterranean Sea aboard whale-watching vessels or monitoring platforms engaging citizen scientists. Samples were analyzed for total DNA concentration using Qubit fluorometry and target DNA concentration with quantitative polymerase chain reactions (qPCR). Key variables tested in the field included water volume (2, 5, and 10 L), sampling timing (immediately after a whale was present and at 5-, 10-, and 20-min intervals), and three filter types (pore sizes of 1.2, 0.8, and 0.45 mu m). Our results illustrate that larger water volumes (10 L), sampling immediately after a whale breach or fluking behavior, and Smith-Root eDNA filters (1.2 mu m pore size) significantly increased eDNA detection probability and signal strength. However, the combination of certain filter types with different water volumes had a significant impact on detection probability, with smaller pore sizes more effectively yielding detections with a lower water volume. These findings provide guidance for future cetacean research initiatives and highlight the potential of eDNA methods in enhancing research and conservation efforts through scalable citizen science-based initiatives.

To investigate the seasonal migratory behaviour of spinetail devil rays, Mobula mobular, across the Mediterranean Sea, we used satellite telemetry to track nine individuals between 2016 and 2021. The species is listed as Endangered in the IUCN’s Red List of Threatened Species and appears to be most vulnerable to fishing impacts when gathering in large assemblages. The only known targeted devil ray fishery harvests significant numbers each winter off Gaza. While broadly distributed during summer across the more productive areas of the western and central portions of the Mediterranean, most tracked rays showed an eastward movement towards eastern Levantine waters during the second half of the year. One individual, tagged off Gaza in March 2016, travelled to Spain before swimming back to the Levantine Sea one year later. Our study corroborates the notion that the species undergoes predictable basin-wide migrations across the Mediterranean Sea, favouring the Levantine waters in late winter and early spring, thanks to the subregion’s milder sea surface temperatures in that time of the year compared to the rest of the Mediterranean. Understanding the species’ seasonal movement pattern in the Mediterranean could support the implementation of robust place-based conservation measures, especially in light of unregulated fishing pressure.

Manta and devil rays are a diverse group of globally endangered elasmobranchs with a complicated taxonomic history. The emergence of genomic techniques has significantly improved our understanding of species units in the group, yet there is one species of devil ray for which uncertainty remains. Mobula rochebrunei (Vaillant, 1879), a pygmy devil ray inhabiting tropical waters of the eastern Atlantic, was recently synonymised with Mobula hypostoma (Bancroft, 1831), its western Atlantic counterpart. However, since there have been no sightings of the species in West and Central Africa for several decades, the revision was based on limited data, and further investigation was recommended. A dedicated monitoring effort in Cameroon recently led to the rare discovery of three pygmy devil rays, providing a unique opportunity to build on recent work. We use a combination of MinION sequencing and morphometric analysis to provide confirmation that pygmy devil rays on both sides of the Atlantic constitute the same species. Crucially, our work highlights the persistence of pygmy devil rays in West Africa despite concerns of disappearance and emphasises the need for urgent conservation action to avoid local extinction.