Hawaiian giant darner

The Hawaiian giant darner (Anax strenuus) is an endemic species of dragonfly belonging to the Odonata order and the Aeshnidae family. Recognized as the largest dragonfly in the Hawaiian Islands, it plays a significant ecological role, yet it can pose specific challenges in managed aquatic environments and agricultural pond systems.

Unlike conventional agricultural pests that damage crops directly, Anax strenuus is considered a pest in the context of aquaculture. Its larvae, known as naiads, are voracious predators that inhabit freshwater ponds. They actively compete with and prey upon juvenile fish, creating substantial economic loss in controlled fishery settings.

The life cycle begins with eggs deposited into aquatic vegetation or the stems of shoreline plants. The larval stage is entirely aquatic and lasts for several months to a year. During this period, the naiads are highly mobile and adapt quickly to changes in their habitat, often outcompeting native fauna.

The harm caused by this insect is primarily concentrated in its predatory behavior. By feeding on fingerlings and beneficial macroinvertebrates, they disrupt the balance of artificial ecosystems. High population densities of Anax strenuus naiads can lead to significantly lower yields for pond farmers who specialize in sensitive fish stocks.

Management and control strategies focus on habitat manipulation to deter egg-laying and larval growth. Key tactics include:

• Removal of submerged and floating weeds to eliminate nesting sites.
• Installation of fine-mesh screens in intake pipes and pond perimeters to prevent access.
• Routine biological surveys to monitor naiad density and manual removal during cleaning operations.