Natural enemies of fish as cause of economic losses in fish ponds

The presence of natural enemies of fish can result in huge economic damage to fish ponds. Direct damages result from the fact that ichthyophagous bird species are capable of eating large quantities of fish in a short time interval, or can cause mechanical injuries to fish which later on become ideal places for the development of secondary infections. In the surviving fish, depending on the depth of the lesions, the healing process takes place either by regeneration or substitution. More serious, bigger damaged areas heal with a scar that can lead to the deforming of parts of the body, and consumers find such fish, which are generally used for human consumption, repellent. According to Schaperclaus, birds can cause even more than 60% losses in carp breeding ponds, in particular in objects where carp fry are maintained. Indirect damages occur when the bird organs are inhabited by larvae or other forms of parasites, which reach the water through feces, and later become fish pathogens through transitory hosts.