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At the European Anglers Alliance (EAA) General Assembly in Vienna, Dr Kurt Pinter (University of Natural Resources and Life Sciences Vienna âeuros BOKU, ProtectFish project partner) presented the first results of Work Package 4, on the effect of cormorants on grayling populations.
Intense predation
On the Upper Drau River, grayling biomass has fallen by 96% since 1989, despite restoration programs. Researchers point to intense cormorant predation as the main obstacle to population recovery. On the Traun River, using electronic chips (PIT-tags), they found that almost half of the tagged grayling had been eaten by the birds.
Rest areas have a clear impact
Even more strikingly, the study shows that a few dozen birds in close proximity to rivers cause far more damage than more distant colonies. A striking fact: the proximity of dormitories proves decisive. The impact of 20 cormorants living less than 25 km from their resting sites is greater than that of a thousand birds further away. These results underline the direct influence of colony geography on predation.
The BOKU will continue its research in the Spittal an der Drau district until 2028, combining annual monitoring, âeurosâeurossupplémentary tagging and wildlife surveillance cameras. The aim is to work with ProtectFish and local communities to develop management measures that balance fish conservation with protection of aquatic ecosystems.
