A sunken WWII hospital ship is now home to devil firefish and rare monk seals

A World War II hospital ship resting on the seabed off the coast of Albania has become an unlikely meeting point for two very different kinds of wildlife: an invasive, venomous fish expanding its range northward, and an endangered seal that had not been documented in the surrounding bay in nearly three decades. Researchers who surveyed the wreck say it illustrates both the promise and the risk of shipwrecks acting as artificial habitat as the Mediterranean warms.

The ship, known as the Po, sank in Vlora Bay in 1941 after being struck by a torpedo fired from a British Fairey Swordfish aircraft during the Greco-Italian War, one of the conflicts folded into the wider Second World War. Divers rediscovered the wreck in 2005, but it had never been the subject of a dedicated biological survey until a research team began documenting it in recent years.

A Hospital Ship Torpedoed in the Greco-Italian War

The Po now sits largely intact on the seabed, where researchers say more than 80% of its surface has been colonized by marine life since it went down more than eight decades ago. Scientific diver Simone Modugno of the University of Ferrara in Italy, a co-author of the new study, and colleagues set out to fill a gap in the record: while Vlora Bay itself had been studied before, there was no historical biological or quantitative data specific to the Po wreck. The team wanted to understand both how the ship’s physical structure had reshaped the surrounding seabed and how marine organisms had moved in to occupy it.

Mapping an Artificial Reef Off the Albanian Coast

Over repeated dives between June 2022 and September 2024, the researchers documented the wreck’s transformation into what ecologists call an artificial reef, a process in which a submerged structure is gradually colonized by marine organisms that use its crevices and dens as shelter and its surfaces as a substrate for algae and other growth. The study catalogued 28 fish species living around the wreck, alongside egg clusters belonging to the Ommastrephidae family of squid, turning a sunken vessel built for war into a functioning, if unplanned, piece of marine infrastructure.

The survey, led by Modugno alongside co-authors R. Castro, I. Pustina, G. Kromidha, Z. Dedej and A. Meçöllari, was published July 27 in Frontiers in Ocean Sustainability under the title “First assessments on marine geomorphology and bio-colonization through the study and survey of the wreck of the Hospital Ship ‘Po’ along the Albanian coasts (Vlora Bay).” The paper’s scope reflects how little formal attention the wreck had received despite decades of local knowledge that it existed: divers had known the general location of the Po since 2005, but no one had systematically recorded which species were using it or how the ship’s hull and cargo holds had altered the surrounding sediment and current patterns.

Devil Firefish Push Deeper Into the Adriatic

Among the animals the researchers found repeatedly patrolling the wreck was the devil firefish (Pterois miles), a venomous species native to the warm coastal waters and coral reefs of the West Indian Ocean and Red Sea, roughly 800 miles, or about 1,300 kilometers, away. Between June 2022 and September 2024, the team observed as many as seven individual firefish around the Po at once, in what the study identified as one of the northernmost confirmed occurrences of the species in the Adriatic Sea. The researchers linked the sighting to a broader pattern of invasive species moving from the Red Sea through the Suez Canal into the Adriatic as sea temperatures climb, with shipwrecks like the Po potentially acting as stepping stones that help the fish establish themselves farther from their native range.

A Monk Seal’s First Vlora Bay Sighting Since 1996

The wreck’s most striking find, however, involved an animal at the opposite end of the conservation spectrum. In August 2023, researchers photographing marine life at the Po captured a Mediterranean monk seal (Monachus monachus) resting inside one of the wreck’s sheltered cavities, the first confirmed sighting of the species in Vlora Bay since 1996. The Mediterranean monk seal typically breeds in sheltered sea caves along Mediterranean coastlines, but tourism and other human activity have pushed the species into more isolated and dangerous caves, compounding threats such as entanglement in fishing gear. The researchers said the sighting suggests monk seals may be using artificial reefs like the Po as resting sites as their natural habitat becomes more fragmented.

Weighing an Invasion Against a Conservation Opportunity

The dual discovery leaves researchers with a genuine tension to navigate rather than a simple success story. Modugno told Live Science that the arrival of devil firefish was not a scientific shock given how well-documented climate-driven range shifts have become, but that the pace of the change still stood out. “What’s perhaps most surprising is the speed with which these climate changes are occurring, acting as a driver and amplifier for the incursions of tropical and alien organisms,” Modugno said, pointing to unusually high salinity and persistent extreme-heat peaks in the region. Modugno added that similar patterns are unfolding beyond Albania’s coast: “For at least three years, I’ve observed a steady and unstoppable increase in fish such as Pterois miles along the Albanian coast, as well as other invasive plant species, mollusks, and shellfish, as well as the spontaneous return of the Mediterranean monk seal.” Modugno said a “serious problem” involving the devil firefish population is likely within the next decade even as the same warming waters and altered coastline appear to be drawing the endangered seals back. The wreck survey was reported by Live Science, drawing on a study published in the journal Frontiers in Ocean Sustainability.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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