European perch

Perca fluviatilis, known as the European perch, is a member of the Perciformes order and the Percidae family. Within the context of aquaculture and commercial fish farming, it is considered an invasive pest or an unwanted predator that significantly impacts the growth and survival rates of economically valuable fish species.

The damage caused by this species primarily affects fry and fingerlings in nursery ponds. As an aggressive predator, the European perch consumes substantial quantities of young fish stock, which leads to reduced yields for fish farmers. Furthermore, it competes directly for food resources, significantly lowering the overall productivity of the artificial aquatic ecosystem.

The life cycle begins in early spring, when water temperatures reach 7–15°C. Spawning involves the deposition of jelly-like egg ribbons onto submerged vegetation, roots, or debris. The development of embryos is highly temperature-dependent, usually lasting a few weeks. The larvae start their life feeding on zooplankton but shift to a piscivorous diet relatively quickly, posing an increasing risk to surrounding fish populations.

The harmfulness of this species is characterized by its rapid population growth and high adaptability. In enclosed ponds, the presence of perch disrupts the intended ecological balance, leading to the depletion of desired fish stocks. Its efficiency as a predator makes it a major concern for intensive aquaculture operations, where survival rates of juvenile fish are critical for commercial success.

Protection and control measures in fisheries include:

• Total pond drainage and disinfection of the pond bottom to eliminate egg clusters.
• Installation of fine-mesh filters on water inlets to prevent the entry of perch eggs or larvae.
• Systematic netting programs aimed at removing both juvenile and mature individuals.
• Maintenance of water quality and management of aquatic vegetation to minimize suitable spawning grounds.