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

Abstract

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.

Prisustvom prirodnih neprijatelja riba mogu da nastanu velike ekonomske štete na ribnjacima. Direktne štete nastaju tako, što su ihtiofagne vrste ptica u stanju da u kratkom vremenskom intervalu pojedu veliku količinu ribe ili kod riba stvore mehaničke povrede, koje kasnije postaju idealna mesta za razvoj sekundarnih infekcija. Kod preživelih riba, zavisno od dubine lezija, sanacioni proces protiče ili regeneracijom ili supstitucijom. Teža, veća oštećenja zaceljuju ožiljkom koji može da uzrokuje deformacije delova tela, a sve to kod potrošača izaziva gađenje i takva riba se ne koristi za ishranu ljudi. Prema Scheperclausu ptice mogu da prouzrokuju čak i više od 60 posto gubitaka na šaranskim ribnjacima, naročito u objektima u kojima je smeštena šaranska mlađ. Indirektne štete nastaju kada u organima ptica žive larveni ili drugi oblici pojedinih parazita koji izmetom dospevaju u vodu, a kasnije preko prelaznih domaćina postaju patogeni za ribe.