The enormous wels catfish is rapidly expanding in German waters. The fish can grow up to 10 feet long and weigh over 300 pounds, making recreational fishermen excited about the prospects of catching one. While biologists aren't yet calling the fish pests, they are puzzled by the boom.
The opinions of fishermen on the wels are diverse. Many are excited about the growing population and are upgrading their equipment -- in order to catch the wels catfish, you need an extremely heavy fishing rod and large pieces of bait. But many traditional fishermen hate the wels. As soon as it appears on the scene, populations of native species seem to drop.
LINK (via: Speigal Online)
The wels catfish lives on annelid worms, gastropods, insects, crustaceans, and fish including other catfishes; the larger ones also eat frogs, mice, rats, and aquatic birds such as ducks.