Storskarvens (Phalacrocorax carbo) ekologi, roll i ekosystemet och effekter på fiskpopulationer: en sammanställning av kunskap och kunskapsbehov

There is a lack of knowledge about the ecology of cormorants in Swedish aquatic ecosystems and how fish populations and ecosystems are affected by cormorants in different areas. Above all, better data on cormorants' food choices, foraging behaviour, numbers and migrations is needed to be able to assess the impact on fish populations and ecosystems. Basic evidence on the biology of cormorants, for a better understanding of their ecological role, should be collected through standardised and internationally coordinated monitoring. Aquatic ecosystems are complex and interconnected, with multiple species and ecological processes interacting. Fish populations are also affected by a number of factors other than predation by cormorants, both biological and non-biological. It can therefore be difficult to separate effects from cormorants from other impacts. It is therefore difficult to draw general conclusions about the impact of cormorants on different fish populations in different areas and during different times. In general, the impact of cormorants on fish populations seems to be small in healthy ecosystems. However, cormorant predation seems to have a negative impact on specific fish populations, especially weak populations that are also negatively affected by other factors. In order to improve the state of knowledge, it is important that management measures aimed at reducing the impact of cormorants on fish populations are followed up scientifically. These management measures should, where possible, be coordinated with other measures in order to better understand which pressures have the greatest impact on different fish populations.