Application of Dietary Content Analysis Using Dropped Feces to Assess Damage to Fisheries by Great Cormorant

The identification of predatory animals is essential to reducing fisheries damage. In this study, we investigated the presence of fish genes in the excrement of Great Cormorant Phalacrocorax carbo at a reservoir in Gifu Prefecture, Japan. DNA metabarcoding analysis revealed that most fish species eaten by Great Cormorants were Japanese Barbel Hemibarbus barbus (number of birds detected/tested, 10/16), Japanese Dace Pseudaspius hakonensis (9/16), and Japanese Smelt Hypomesus nipponensis (9/16), whereas the genes of released fish were detected in only a few samples. Our findings suggest that cormorants living at the reservoir rarely consumed released fish.