Multiple lines and levels of evidence for avian zoochory promoting fish colonization of artificial lakes

Understanding how obligate freshwater organisms colonize seemingly isolated ecosystems has long fascinated ecologists. While recent investigations reveal that fish eggs can survive the digestive tract of birds and successfully hatch once deposited, evidence for avian zoochory in natura are still lacking. Here, we used a multiple lines and levels of evidence approach to demonstrate plausible bird-mediated colonization of lakes by the European perch (Perca fluviatilis). We studied a set of newly-formed artificial lakes that the public is either prohibited to access because of gravel extraction or allow to access (mainly for angling). The motivating observation is that a large proportion of prohibited-access lakes (>80%) were colonized by European perch while stocking by anglers and managers never occurred. Three supplementary lines of evidence supported avian zoochory. First, European perch spawning occurs when waterfowl abundance is very high. Second, European perch lays sticky eggs a..., ,