Nereis pelagica

Nereis pelagica, commonly known as a marine ragworm, is a polychaete worm belonging to the family Nereidae. In the professional aquaculture sector, it is often considered a significant pest that can infiltrate recirculating aquaculture systems (RAS) and seawater farming facilities. Being a resilient and opportunistic predator, it can disrupt the delicate environment required for cultivating sensitive aquatic species.

The organism primarily threatens farms specializing in shrimp, shellfish, and macroalgae production. By burrowing into substrates and feeding on soft tissues, the worm causes structural damage to the habitat and directly kills juvenile stages of the target crops. This predation leads to reduced survival rates and significant yield losses for commercial producers who rely on stable ecological conditions.

The life cycle of Nereis pelagica involves a planktonic larval stage followed by a sedentary benthic stage. This biological flexibility allows the pest to colonize new systems via water intake pipes easily. Once established in the sediment or biofilters, they reproduce rapidly, making it challenging to eradicate the colony without precise and targeted biological or mechanical interventions.

Beyond direct consumption of livestock, the worm causes indirect damage by destabilizing the substrate. As these worms tunnel through the sediment, they re-suspend organic waste, which leads to spikes in turbidity and reduces dissolved oxygen levels. These environmental shifts stress the farmed species, making them more susceptible to secondary infections and reducing overall productivity across the facility.

Effective management strategies require a multi-faceted approach. Primary measures include installing ultra-fine mesh filters at intake points to prevent larval entry. Regular maintenance and deep cleaning of bio-tanks are essential to remove mature worms and their burrowing networks. In high-density systems, selective biological control agents or precise water treatments are often employed to manage population growth while ensuring the safety of the main aquaculture crops.