After being hauled aboard, the fish immediately inflated and produced clicking sounds. The capture extends the species’ documented northern boundary beyond previous Adriatic and Mediterranean records, although the observation of one individual does not by itself establish how widespread the population has become in northern Croatian waters. The fish was transported to the Laboratory of the Faculty of Natural Sciences in Pula for species identification, measurements, examination of its gonads and analysis of stomach contents.

Researchers identified it as Lagocephalus sceleratus , commonly known as the silver-cheeked toadfish. Its total length was 522 millimetres, standard length was 433 millimetres and weight was 1,330 grams. Macroscopic examination of the gonads determined that the specimen was male.

The study is a single-specimen record with anatomical, dietary and geographic observations; it does not provide a population estimate for northern Adriatic toadfish or quantify changes in their abundance around Croatia. The species was first recorded in the Mediterranean off the southeastern Aegean coast of Turkey in 2003. Subsequent records showed its presence across much of the eastern basin, particularly along the coasts of Greece, Turkey, Lebanon, Egypt, Cyprus, Malta and Tunisia, with reports extending to Gibraltar and the Black Sea.

Thirteen pufferfish species have been detected in the Mediterranean, including 11 non-indigenous species, and 11 have established populations according to the cited regional records. The silver-cheeked toadfish is among the most conspicuous of these arrivals. Habitat-suitability models described in the study predict that L. sceleratus is most likely to occur in coastal areas, with the highest modeled suitability in the eastern Mediterranean, especially along the coasts of Greece and Turkey.

The models also identify additional suitable areas along southern Italy, near the Strait of Gibraltar and in parts of the western Mediterranean, while some central and western areas receive lower suitability ratings. A merged distribution indicates that much of the Mediterranean is suitable for the species except for certain central and western regions. These are spatial model predictions rather than measurements of the fish’s current abundance, and the Medulin Bay capture lies outside the eastern area identified as having the highest predicted suitability.

The 2024 fish was the fifth reported L. sceleratus occurrence in the Adriatic Sea and the fourth on its eastern side. The first Adriatic specimen was caught in October 2012 north of Jakljan Island in southern Croatia, followed by a record near Tribunj in 2013 and another near Vodice in 2014. A fish was also documented on the Italian side of the Adriatic near Trani in Puglia in 2014, and another occurrence was reported in 2019.

The Medulin Bay animal was caught farther north than all of those records. The reported sequence of locations and dates documents the species’ presence across the Adriatic and identifies the latest capture as its northernmost, without establishing a uniform or uninterrupted expansion along the basin’s coasts. Ocean circulation may facilitate the movement of warm-water species into new Adriatic areas.

The Adriatic current flows north to northwest along the coasts of Albania and Croatia, reaches the Istrian Peninsula and then turns southeastward along Italy. The study notes that this circulation can assist the transport of larvae and juvenile fish. Medulin Bay also shares oceanographic features with the neighboring Kvarner area, including deeper water and somewhat higher bottom temperatures than parts of the shallow northern Adriatic shelf along western Istria.

Dense water production on the shallow shelf is contrasted with more frequent bottom-layer renewal in Kvarner Bay, which occurs annually rather than on the longer cycles found in some deep Adriatic basins. The authors identify these conditions as potentially favorable for thermophilic species, including other non-native organisms recorded nearby, but the record itself does not establish the route by which the captured fish reached Medulin Bay. Stomach analysis identified bivalve shells, gastropod shells, fragments of sea-urchin skeletons and particles of inorganic material.

Most prey could not be identified below a relatively high taxonomic level because the toadfish’s beak-like jaws crush food so thoroughly that recognizable species-level remains are rarely recovered. The observed contents nevertheless document the consumption of mollusks and armored benthic animals. The species’ powerful dentition allows it to feed on both pelagic and benthic organisms, including crustaceans, sea urchins and barnacles.

The Medulin Bay stomach contents therefore fit the species’ broad diet, but a single fish cannot establish how frequently different prey categories are consumed or how local predation changes across the Adriatic. The growing presence of L. sceleratus has consequences for coastal fisheries as well as marine monitoring. In some Mediterranean coastal areas, the species became an increasingly important component of small-scale fishing catches less than a decade after its first detection, creating socioeconomic repercussions.

Proposed measures in invaded areas include more robust fishing gear, changes in fishing tactics during periods when the fish are frequently present and exploration of their commercialization. The study identifies targeted removal during the spawning period as the principal control priority for decision-makers. Such proposals remain management recommendations rather than interventions evaluated by the present single-catch report.

The authors also emphasize that the changing Mediterranean biodiversity profile does not yet establish the precise effect of warm-water arrivals on trophic webs or ecosystem functioning. Human health adds another reason to track the species’ distribution. The silver-cheeked toadfish is described as aggressive and has been reported to bite people approached in coastal water.

Although such incidents are rare, the cited southern and eastern Mediterranean cases include severe injuries and partial finger amputation. The growing occurrence of the fish in coastal areas therefore creates a particular concern for swimmers in frequently visited tourist zones. The species is also highly toxic, which the study links to the need to prevent its marketing and consumption.

The authors call for education of medical staff, tourism workers, marine-recreation professionals and the public, along with guidance from Croatia’s Directorate of Fisheries for fishers handling accidental catches. They describe this as a need for coordinated preparedness, not as a response tested by the reported specimen. Regulatory gaps complicate efforts to address invasive marine species.

European Union regulation on invasive species focuses mainly on freshwater and terrestrial ecosystems, while many marine species are excluded because of scientific uncertainties and conflicts between conservation goals and fisheries interests. Croatian national policy addresses some marine species in aquarium-related contexts but does not provide comprehensive controls for wild populations such as L. sceleratus . The study therefore recommends targeted national and local action involving enforcement, catch-handling information, public education and targeted removal.

It also presents the Medulin Bay record as an example of the value of citizen science: local fishers, recreational anglers and marine enthusiasts have contributed to the detection of Croatian records, and mobile reporting systems could improve early detection. The finding confirms the northernmost Mediterranean occurrence while leaving the abundance, ecological effect and future movement of the species in the northern Adriatic unresolved.

Subject of Research: A single-specimen record of the silver-cheeked toadfish in Croatia’s northern Adriatic

Article Title: Northernmost Mediterranean record of the silver-cheeked toadfish, Lagocephalus sceleratus ( Actinopterygii , Tetraodontiformes , Tetraodontidae )

Article References: Iveša, N., Buršić, M., & Dulčić, J. (2025). Northernmost Mediterranean record of the silver-cheeked toadfish, Lagocephalus sceleratus (Actinopterygii, Tetraodontiformes, Tetraodontidae). Acta Ichthyologica et Piscatoria, 55, 77-81. https://doi.org/10.3897/aiep.55.146945

Image Credits: AI Generated

DOI: 10.3897/aiep.55.146945

Keywords: silver-cheeked toadfish, Lagocephalus sceleratus, northern Adriatic, Mediterranean Sea, Croatia, invasive species, Lessepsian migration, pufferfish, coastal fisheries, citizen science, Northernmost, Mediterranean

Offshore freshened groundwater is water stored in the pores of sediments and fractures of rocks below the seabed, with a total dissolved solids concentration lower than that of seawater. These reserves are far from exotic curiosities. They have been documented on continental shelves around the world, from the New Jersey Shelf in the United States to the Canterbury Bight in New Zealand, the Pearl River Estuary in China, and the waters offshore Malta. Coastal communities have known about and used freshwater discharging from the sea floor for centuries, with records stretching back as far as 1,000 BC. What has been missing, according to the research team led by Ariel T. Thomas of the University of Malta, is a rigorous, cost-effective method for deciding which of these buried reservoirs are actually worth pursuing before expensive site-specific surveys are commissioned.

The new study addresses that gap with a two-step, data-driven framework built entirely on openly available datasets. In the first step, the researchers compiled a geospatial database combining confirmed OFG occurrences from the OFF-SOURCE database, predicted OFG volumes for coastal unconsolidated aquifers, global bathymetry, paleo-coastline reconstructions from the Last Glacial Maximum, regional water stress indicators from the Aqueduct 3.0 platform, and the locations of existing desalination plants and offshore oil and gas platforms. Sites were then classified into three feasibility tiers based on four cost-relevant criteria: seafloor depths of less than 125 metres, where offshore drilling is considerably cheaper and technically simpler; distances of less than 15 kilometres from the shoreline, corresponding to the upper range of typical infield pipeline lengths; the presence of nearby desalination plants; and the existence of offshore platforms that could be repurposed for water exploration.

The screening exercise produced a striking result. Of seven potential OFG sites evaluated, only one met all four infrastructure criteria alongside high regional water stress: the Northern Adriatic Sea offshore Rimini, Italy. Several boreholes in this area indicate salinity levels below 1 gram per litre at shallow seafloor depths of less than 30 metres, all within 15 kilometres of the coast, with multiple offshore platforms and desalination plants already operating along the nearby shoreline. The analysis also flagged new high-potential exploration zones offshore southern Spain, Belgium, and Malta, regions where high water stress and existing infrastructure co-exist even though OFG has not yet been confirmed there. According to the authors, this finding supports a strategic shift from reacting to incidental discoveries toward proactive exploration targeting in areas with the highest pre-existing economic viability.

With the Tier 1 site identified, the team turned to a detailed quantitative assessment of the Northern Adriatic resource. They extracted the depths and thicknesses of fresh and brackish water intervals from 37 borehole datasets, many drawn from Italy’s public ViDEPI archive of hydrocarbon exploration wells, and used kriging interpolation on a 400-metre grid to map the OFG body across an area of 9,343 square kilometres. Cross-validation confirmed a well-calibrated interpolation, with a root mean square error of 152.9 metres and a standardised error ratio of 0.97. The mapped interval thicknesses range from about 300 metres near Venice to roughly 500 metres along the coast near Rimini, thinning to approximately 170 metres at the farthest offshore extent of the study area.

A key geological insight emerged from this mapping. The spatial distribution of the freshwater body reveals an elongated, channelized trend that correlates directly with the reconstructed position of the Po River paleochannel, the ancient riverbed that flowed across the exposed Adriatic shelf during the Last Glacial Maximum, when sea levels were far lower than today. The researchers conclude that this proto-riverbed most likely acted as a primary conduit for meteoric recharge during sea-level lowstands, allowing rainwater to infiltrate deep into the shelf sediments. This correlation, they argue, marks paleochannels as high-priority exploration targets not only in the Adriatic but in similar deltaic settings worldwide.

To quantify the resource while honestly accounting for uncertainty, the team ran a Monte Carlo simulation of one million iterations. Because the legacy oil-exploration wells only recorded salinity data from depths of roughly 200 to 400 metres below the seabed, the shallower overlying interval of unknown salinity represented the dominant uncertainty. Drawing on empirical fresh-fraction analysis from eight wells within the study area, which yielded freshwater fractions ranging from 14 to 100 percent with a mean of 72 percent, the researchers assigned probabilistic distributions to each volumetric component. The results are remarkable: a conservative mean volume of 766 cubic kilometres based on confirmed freshwater intervals alone, rising to a broader mean estimate of 2,413 cubic kilometres when the overlying interval is probabilistically included, with an 80 percent confidence interval spanning 1,516 to 3,215 cubic kilometres. For context, the adjacent Venetian-Friulian Plain currently extracts groundwater at 48.6 cubic metres per second against a recharge rate of only 43.7 cubic metres per second, a deficit the estimated offshore reserve exceeds by a factor of more than 4,000 in annual terms.

The economic case rests on a simple physical principle: the energy required to push water through reverse-osmosis membranes scales with salinity. Energy typically accounts for 40 to 50 percent of the cost of seawater reverse osmosis, and the pressure needed to overcome osmotic pressure is the single largest component. Using industry-standard simulation software calibrated to state-of-the-art efficiency, the researchers found that desalinating OFG at salinities of 1 to 10 grams per litre requires only about 23 to 56 percent of the membrane energy needed for seawater at a 75 percent recovery rate, compared with the 35 to 50 percent recovery typical of seawater plants. Applied across a full cost model for a large-scale facility, this translates into total desalination costs 10.6 to 18.4 percent lower than seawater over the same salinity range. Because previous work has estimated the at-sea extraction costs of OFG at less than 10 percent of overall costs, the authors conclude that OFG could plausibly be cost-competitive with, or cheaper than, conventional seawater desalination.

The framework is not a green light for immediate exploitation. The authors caution that a full economic assessment, including capital costs for offshore drilling, pipelines, and infrastructure conversion, remains necessary, and that any future development would need careful environmental evaluation. Sustained offshore pumping could reduce onshore groundwater availability, promote seawater intrusion into coastal aquifers, and alter submarine groundwater discharge, with knock-on effects for benthic ecosystems. Subsidence is a particular concern in the Northern Adriatic, where land sinking already threatens cities such as Venice. Brine effluent from brackish-water desalination, though considerably less saline than seaward brine, would still require management. What the study delivers instead is a replicable methodology: a transparent, data-driven bridge from regional prioritisation to site-specific feasibility that water-stressed coastal nations can apply wherever borehole records and open datasets exist. As climate change intensifies pressure on coastal aquifers that already supply more than one billion people worldwide, the vast freshwater volumes quietly resting beneath shallow continental shelves may soon move from geological curiosity to strategic asset.

Subject of Research: Infrastructure-based prioritization and cost analysis of offshore freshened groundwater in the Northern Adriatic Sea

Article Title: Infrastructure-based prioritization and cost analysis of offshore freshened groundwater: a Northern Adriatic case study

Article References: Thomas, A. T., Tschaikowski, J., Katz, D., & Micallef, A. (2026). Infrastructure-based prioritization and cost analysis of offshore freshened groundwater: a Northern Adriatic case study. Frontiers in Water, 8, Article 1828540. https://doi.org/10.3389/frwa.2026.1828540

Image Credits: AI Generated

DOI: 10.3389/frwa.2026.1828540

Keywords: offshore freshened groundwater, desalination, Northern Adriatic, water resources, reverse osmosis, Po River paleochannel, Monte Carlo simulation, unconventional water, Infrastructure-based, prioritization, cost, analysis

The central finding is staggering in its implications for how prehistoric life is understood in the region. Land once roamed by hunter-gatherers and later tended by early farmers now lies deep beneath the sea. The present-day Venice Lagoon, famous for its island city built on marshy, muddy ground, was once dry land that lay kilometres from the coast. The same is true of other towns in the lagoons further east, such as Grado, and even present-day coastal cities like Trieste would once have stood in hills overlooking swamps and lagoons below. In other words, some of the most archaeologically significant terrain in the region is invisible to conventional, land-based survey, hidden beneath seabed sediments that have accumulated over millennia.

Technically, the study is a palaeolandscape reconstruction built from two complementary strands of evidence. The researchers combined existing data from the analysis of sediment cores with new, high-resolution geophysical data acquired by OGS. Sediment cores allow scientists to identify different types of deposits, each characteristic of a particular environment, whether open marine, coastal barrier, lagoon, marsh or floodplain. Geophysical surveys, in turn, reveal the buried architecture of these deposits across wide areas of the seabed. By identifying the sediment types and modelling successive flooding episodes, the team was able to trace the backward shifting of coastal barriers, deposits running parallel to the shore, and the back-barrier systems, the marshy areas that lay beyond them. The result is a sequence of maps showing how the coastline retreated inland, stage by stage, across five millennia.

The timeline that emerges is anything but smooth. The reconstruction identifies a rapid rise in sea level around 8,400 BC that created tidal channels, marshes, sandbanks and large lagoons, followed by a more stable phase in which these features could persist and develop. Then came a large rise, a total of eight metres in the 1,200 years leading up to 6,600 BC, during which the sea repeatedly created, subsumed and recreated lagoons and marshes, pushing kilometres inland. A further major rise of up to five metres after 6,000 BC again shifted coastal features landward. Finally, after about 5,800 BC, the origins of the lagoons and the landscape recognisable today began to form. At times, the rate of rise reached up to 25 millimetres per year, a pace that would have been plainly visible within a single human lifetime.

That pace matters for understanding what prehistoric communities actually experienced. A rise of 25 millimetres per year translates into roughly a metre of relative sea level change across two or three generations, enough to permanently abandon settlements, alter hunting grounds and redraw the geography of trade and movement. The study highlights the constantly changing environment that Mesolithic hunter-gatherers had to cope with, as rising water altered habitats, resources and the availability of food such as plants, fish and animal prey. Coastal barriers were overrun and rebuilt; lagoons formed, filled and re-formed. Successive shaping and reshaping of coastal features influenced the lives of Mesolithic and Neolithic people and the development of local communities, as the sea swallowed features it had previously formed, shaped new ones, and eventually produced the origins of the modern coast.

Samuele Ongaro, lead author and PhD researcher at the University of Southampton, an archaeologist by training, emphasises why these drowned terrains matter. Submerged landscapes, he notes, are an important missing piece in the study of prehistory, especially in the Northern Adriatic, because they hold many secrets about how ancestors lived and how they were connected to the land. According to Ongaro, the results of the research allow the reconstruction of these lost landscapes, the environments they hosted, how they changed over time, and what significance they might have held for prehistoric populations, which he describes as a fundamental step for future archaeological research in the area. The framing is significant: rather than treating the seabed as a blank between terrestrial sites, the study treats it as a continuous, inhabited landscape worthy of systematic investigation.

The environmental variety of the reconstructed coast also helps explain why people were drawn to it in the first place. As Ongaro points out, the variety of coastal environments, lagoons, river deltas, marshes and swamps, would have been an attractive landscape for foragers and hunters, offering diverse and productive ecological niches. Yet the flat nature of the landscape also made it prone to significant land loss, and communities were forced to adapt over time, choosing where to hunt, fish and settle. This tension, between ecological richness and geographic vulnerability, is central to the study’s archaeological implications. The team hopes further study will reveal more about how communities shifted their activities in response to coastal flooding, and how this eventually affected the advent of farming in the region by Neolithic people, one of the most debated transitions in European prehistory.

From the marine geoscience side, the collaboration demonstrates the value of integrating geological and geophysical data. Dr Federica Donda, a marine geologist from the Geophysics section of OGS and co-author of the paper, comments that the study shows how integrating geological and geophysical data makes it possible to reconstruct the environmental evolution of areas that are now submerged, while highlighting that the seabed is an integral part of archaeological heritage. In her view, a significant portion of the areas frequented by ancient populations is now underwater, and their history and evolution cannot be understood through terrestrial archaeology alone. This is a pointed methodological claim: any model of Mesolithic or Neolithic settlement in the Northern Adriatic that ignores the drowned plains is, by definition, incomplete, because it excludes the very terrain where much of early coastal life unfolded.

The paper, titled Palaeolandscape reconstructions for the Northern Adriatic: Inundation models, depositional environments, and potential archaeological implications, underscores the potential of palaeogeographic reconstructions for studying the evolution of past societies. By returning to archaeological research a piece of territory that is no longer visible today, but which for thousands of years was part of the European landscape, the work opens a path toward predictive models of where submerged prehistoric sites might survive. The method of research is described as computational simulation and modelling, combining inundation models with depositional interpretations, an approach that could be applied to other drowned coastlines around the world where post-glacial sea level rise has erased the record of early coastal adaptation.

For a region whose modern identity is bound up with the fragile balance between water and land, from the Venice Lagoon to the gravelly shores of Trieste, the study offers a deep-time perspective on an ongoing process. The coast that residents and visitors know today is merely the latest configuration in a long sequence of flooding, barrier migration and lagoon formation that began when the last ice age ended. What the Southampton and OGS team has shown is that this sequence is readable in the sediments beneath the seabed, and that within those sediments lie clues to how some of Europe’s earliest coastal communities lived, moved and adapted as the sea rose around them. The next stage of research, the authors suggest, will focus on pinning down how human activity responded to each successive inundation, turning a drowned landscape into a map of prehistoric resilience.

Subject of Research: Prehistoric sea level rise and coastal landscape change in the Northern Adriatic

Article Title: Study reveals how prehistoric coastal flooding shaped the Northern Adriatic

Article References: Study reveals how prehistoric coastal flooding shaped the Northern Adriatic. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Northern Adriatic, sea level rise, Venice Lagoon, Mesolithic, Neolithic, submerged landscapes, palaeogeography, coastal barriers, lagoons, sediment cores, geophysics, Quaternary Science Reviews