Abstrakt
The Great Cormorant Phalacrocorax carbo is a widespread piscivorous water bird. Cormorant predation on fish stocks has been causing widespread conflicts between recreational anglers and environmentalists.
This study aimed to evaluate the difference in fish catches between anglers and overwintering cormorants. We collected and analysed cormorant pellets in North Bohemia (Czech Republic) during winter.
We compared species composition and size of fish caught by cormorants to species composition and fish size in catches of anglers from the most important fishing grounds in the area, calculating a dietary overlap between cormorants and anglers. Roach Rutilus rutilus dominated in cormorant diet while common carp Cyprinus carpio dominated in catches of anglers.
Cormorants targeted significantly different fish species of different sizes than anglers did. Cormorants mostly preyed upon small fish of lower angling value while anglers mostly took large fish of higher angling value.
Dietary overlap between catches of cormorants and anglers was low. Cormorants mostly preyed upon fish species and sizes that are generally very abundant while anglers mostly selected rare stocked fish species and sizes with an addition of bream Abramis brama.
In case of fish species with high angling value, cormorants took almost exclusively fish legally undersized for anglers.