Monitoring of European shag populations

The European shag (Phalacrocorax aristotelis desmarestii) is a predatory cormorant that often eats into fishers’ and aquaculture producers’ profits. To better understand their behaviour and interactions with fish species, researchers monitored three coastal N2000 shellfish farms, where the majority of the Slovenian shag population roosts. Monthly boat trips were undertaken between July and September using ESAS (European Seabirds at Sea) methods, and shag bycatch information from the Fisheries Research Institute of Slovenia was used for the assessment.

Density and biometric parameters of Gobius niger, the shag’s main prey, was assessed by a diving team; videorecording with a camera on sleds (SKICAM) dragged along transects; analysis of Gobius niger bycatch data; and analysis of shag spew content.