| Summary: | Verkefnið er lokað til 15.08.2022. Global waterbird populations have been declining over the past few decades. Disturbances and hab-itat loss caused by anthropogenic activities are some of the main drivers of these declines. While shellfish aquaculture is a globally increasing sector, its influence on waterbird populations is not well studied. This study aimed to fill this gap by analysing waterbird trends across the island of Ireland in relation to intertidal shellfish aquaculture. Population indices were calculated for eight representative waterbird species wintering in Ireland: Light-bellied Brent Goose (Branta bernicla hrota), Mallard (Anas platyrhynchos), Shelduck (Tadorna tadorna), Wigeon (Anas penelope), Curlew (Numenius arquata), Dunlin (Calidris alpina), Oystercatcher (Haematopus ostralegus), and Redshank (Tringa totanus). A total of 37 sites were included in both Northern Ireland and in the Republic of Ireland (RoI). Population trends were then analysed for each species at all-Ireland, national, and at regional level between winter 1994/95 and 2018/19. The influence of the presence of aquaculture was ana-lysed using negative binomial GLMs. Overall, decreasing trends in population indices were found for five out of eight species over 25 years. Only the Light-bellied Brent Goose showed an increasing population trend, while Dunlin experienced the most declines across all levels. Redshank and Oys-tercatcher populations remained mostly stable. Aquaculture presence was found to have a significant negative influence on the indices of six species, while it positively affected the indices of Mallard and Wigeon. Within the RoI, the absence of aquaculture had an overall positive effect on waterbird indices, but the effect varied between regions. For migrating waterbirds in particular, different factors could have impacted the species at population level, and at different stages of their flyways. These factors include, among others, agriculture practice, hunting, disturbance, poor productivity, or habitat loss ...
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