Green sunfish

Systematic position: The green sunfish (Lepomis cyanellus) belongs to the order Perciformes and the family Centrarchidae. Originating from North America, this species is recognized globally as a significant invasive threat due to its aggressive predatory behavior and extreme environmental tolerance, allowing it to colonize diverse aquatic habitats.

Affected industries: While not a crop pest in the traditional agricultural sense, it is a major nuisance in aquaculture and commercial fisheries. The green sunfish poses a serious threat to pond management by preying on the fry of valuable food fish species, effectively competing for food resources and disrupting the productivity of fish farms.

Biology and development: This species is characterized by its high plasticity, capable of thriving in hypoxic (low oxygen) waters and extreme temperatures. Spawning typically occurs from spring through mid-summer. Males establish and guard nests in the substrate, ensuring a high rate of offspring survival and rapid population expansion in closed or semi-enclosed aquatic systems.

Nature of damage: The primary harm is ecological and economic disruption. By outcompeting native fish and consuming the larval stages of economically significant species, the green sunfish can devastate the biomass yield of small ponds. Its presence often leads to stunted populations of desired fish, as the sunfish efficiently strips the pond of its invertebrate and juvenile fish food sources.

Control measures: Management of green sunfish requires a strategic approach:

• Complete drainage and drying of ponds to eliminate populations.
• Application of rotenone or other piscicides where permitted by environmental regulations.
• Introduction of apex aquatic predators (e.g., largemouth bass) to keep sunfish numbers suppressed.
• Strict prevention of stocking infected water bodies and screening of water inlets.