Released goldfish threaten amphibian breeding ponds in Vorarlberg

Released goldfish are eating amphibian larvae in breeding ponds in Vorarlberg, threatening frogs, toads and newts, ORF reports. Thousands of amphibians are carried across roads by volunteers each spring, while the number of sites requiring protection has increased in recent years.

Protective fences and collection buckets are installed at about 30 danger points for species including common toads, grass frogs and alpine newts. The fences prevent the animals from reaching the road and guide them into buckets sunk into the ground. About 130 volunteers check the buckets at least once a day, or twice during sudden changes in weather, before releasing the animals at a breeding pond.

The largest migration point is at Levner Weiher, a pond in Feldkirch, with about 2,500 animals per season. It is followed by Reutestraße in Hohenems, with about 1,800 animals. The report does not provide figures for every migration point.

The Vorarlberg Amphibian Coordination Centre, a state-run body, has been monitoring more sites after new problem areas were reported. The report says some breeding ponds near migration routes are increasingly silting up and should be maintained. Where suitable ponds are unavailable, replacement ponds are considered important.

In one case in February 2026, a water wheel was shut down on the same day a warning was received because it had become a deadly danger to grass frogs.

Permanent structures such as amphibian tunnels beneath roads are described in the report as the best solution. They protect animals during both their spring migration and their return journey, work regardless of weather or volunteer availability, and can also benefit other small animals.

However, surveys are needed to determine where such structures should be built. Detailed surveys were carried out in Satteins in 2024 and in Götzis near St. Arbogast in 2025. The report says no detailed survey of the main migration routes was conducted this year because the budget was too limited as more ponds required monitoring.

The fences also provide data on population sizes and trends. Volunteers are expected to record the number of animals by species during each inspection. The inatura nature exhibition in Dornbirn again called for amphibian monitoring this year, and volunteers are still needed to help rescue grass frogs and other species.

Amphibians are among the most threatened animal groups worldwide. Vorarlberg’s Red List also shows a continuing decline. Habitat loss, expanding and increasingly busy transport networks, pavement edges, drainage shafts and drainage channels can all threaten the animals by dividing their habitats or creating barriers and traps.

The report identifies released goldfish as another problem. The fish eat amphibian larvae and are almost impossible to remove once they are in a pond. Draining the pond or leaving it dry for several weeks in winter are the only methods described as effective. The report says goldfish continue to be released into the wild despite a legal ban, affecting breeding ponds particularly in Dornbirn, Schwarzach, Nenzing and Tschagguns.

Goldfish and tadpoles may coexist in larger ponds with abundant vegetation, structures and hiding places, the report says. Common toad tadpoles are an exception because bitter substances in their bodies mean they are rarely eaten by fish.

The environmental organisation WWF also warns against releasing goldfish into the wild, describing them as being “as alien as aliens” to frogs.