Acilius diving beetle

The genus Acilius belongs to the Dytiscidae family within the order Coleoptera. In the context of aquaculture and agricultural water management, these insects are considered significant pests that threaten the survival of fish populations in commercial ponds and hatcheries.

These beetles primarily damage fish fry and eggs. As voracious aquatic predators, both adults and larvae prey on juvenile fish, which negatively impacts the profitability of aquaculture ventures. They are particularly dangerous in nursery ponds where fish density is high and shelter for predators is available.

The biological cycle of the Acilius beetle consists of four stages: egg, larva, pupa, and adult. Eggs are laid into the tissues of submerged aquatic plants. The larvae, which are highly mobile and equipped with sharp, sickle-like mandibles, hunt for prey in the water column. Pupation occurs on land in moist soil, marking the transition from an aquatic life stage to an adult beetle.

The damage caused by these insects is mechanical and digestive. The larvae utilize extra-oral digestion, injecting enzymes into the prey to liquefy its tissues. This hunting strategy allows them to consume numerous fish fry, significantly reducing the survival rate of the fingerlings and causing considerable economic losses for farmers.

Effective management strategies focus on habitat modification and mechanical control. Key practices include:

• Drainage and desiccation of ponds between production cycles to eliminate larvae.
• Removal of excessive aquatic weeds where beetles lay eggs and hide.
• Installation of fine-mesh screens on water intake pipes to prevent adult beetles from entering ponds.
• Manual removal of adults using specialized nets during the early stages of pond colonization.