Wildlife Damage Management, Internet Center for


Date of this Version

February 1989


One hundred forty-eight double-crested cormorants (Phalacrocorax auritus) were collected in October-December 1988. Some were collected while actively feeding, but most were collected at loafing or roosting areas. Of the 135 with fish in them, 79% contained gizzard shad (Dorosoma cepedianum) and 16% contained centrarchids (mostly Lepomus sp.). The rest contained a variety of aquaculture (commercially raised) fish. Fish prey weights were estimated from total length of prey items and use of published length-weight tables. Total weights of prey ranged from 39 to 4558 with a mean of 185g. This was felt to be a conservative estimate of 1/2 daily consumption. Thus, these birds appear to be eating approximately 370g (0.81 lbs.) of fish per day. Potential impact at aquaculture facilities will depend on the value of the crop.