Kategorie: News
aquatil shows what’s really going on in our lakes at InterDive
From September 24 to 27, 2026, aquatil’s bullfrog team will once again be at InterDive in Friedrichshafen - in Hall B5 at Booth 141. The focus will be on an animal whose size surprises even experienced divers: the invasive North American bullfrog, whose tadpoles can grow up to 20 centimeters in length.
We first reported on this growing problem in the northern Upper Rhine region back in 2021, when dedicated recreational divers around Karlsruhe began removing tadpoles from affected lakes during authorized collection efforts. At that time, five lakes in the Karlsruhe area were affected, and around 20,000 tadpoles were collected annually - with the stated goal of slowing population growth, not completely solving the problem. A lot has happened since then: In 2025, we accompanied a nighttime collection effort at the Linkenheim quarry pond, during which Baden-Württemberg State Secretary Dr. Andre Baumann, himself a recreational diver, pitched in. His conclusion at the time: “For every reproductive-age female that is tracked down and removed, the laying of 10,000 to 20,000 eggs can potentially be prevented.”
A project that relies on recreational divers
The current funding project “Bullfrog Control in Baden-Württemberg” is initiated and led by Prof. Dr. Ralph Schill, who conducts research on biodiversity, stress adaptation, and non-native species at the University of Stuttgart and is also the managing partner of aquatil gGmbH. The project is funded by the Baden-Württemberg Nature Conservation Fund with approximately 152,000 euros from earmarked proceeds of the GlücksSpirale lottery. Schill is also responsible for science and the environment on the board of the Association of German Recreational Divers (VDST) - a dual role that works to his advantage: Because released animal species, in particular, cannot be easily mapped - unlike plants (“they don’t run away,” as Schill himself once put it” - he specifically relies on the observational skills of recreational divers.
Since around 2012, researchers have been documenting their observations during scientific dives. This has since evolved into a project employing a variety of methods: Adult animals are fitted with transmitters to track their movement patterns between land and water.
Furthermore, non-invasive telemetry on tadpoles has, for the first time, provided evidence of specific migratory behavior toward underwater overwintering sites - accompanied by skeletal chronological findings that show some larvae can even suspend metamorphosis over the winter. The toolkit is supplemented by species-detection dogs - deployed in Germany for the first time - that specifically track down overwintering frogs.
On the fair stage, the team will report directly from the field on all three days: On Friday, September 25, at 12:20 p.m., the presentation titled “Eye to Eye with the Giant Tadpole in Our Lakes” will focus on the fieldwork itself; on Saturday at 2:10 p.m., this will be followed by “With a Mask and Fins to the Giant Tadpoles,” before Sunday wraps up at 3:40 p.m. with “On the Trail of Bullfrogs in Our Lakes.”
More Than Just a Frog
While the bullfrog is the main focus, it’s not the only topic at the booth: Visitors will also learn how other invasive species are spreading in local waters and what consequences this has for the ecosystems there. This aligns with aquatil’s broader portfolio, which also includes organizing a citizen science monitoring project for the quagga mussel in collaboration with the University of Stuttgart’s Scientific Diving Group (WiTUS), as well as the free online lecture series ReefExplorer on coral reefs.
Anyone interested can pick up a free copy of the booklet “Ochsenfrosch-Wissen” at the booth - which provides background information on the frog’s lifestyle and range. After years of dedicated fieldwork and a growing scientific foundation, this renewed presence at InterDive demonstrates one thing above all: Interest in the giant tadpole underwater remains strong - and with it, the need to continue working on solutions together with the diving community.
Further information:
aquatil gGmbH
Taucher.Net / DiveInside – Non-native Species and the Problem with Bullfrogs (2021)
Taucher.Net / DiveInside – Bullfrog Hunt at the Linkenheim Quarry Lake (2025)
Taucher.Net / DiveInside – Focus on the Bullfrog (2026)
University of Stuttgart, Institute for Biomaterials and Biomolecular Systems