Eirene viridula

Eirene viridula is a species of hydrozoan polyp belonging to the order Leptothecata and the family Eirenidae. It is a cosmopolitan organism recognized for its dual life cycle, which includes a sessile polyp stage and a planktonic medusa stage. While primarily a part of marine biodiversity, in the context of aquaculture, it is categorized as a biofouling agent that can disrupt industrial operations.

The biology and development of this species are characterized by the rapid colonization of various hard substrates. Polyps attach to surfaces such as nets, cages, and pipes, where they form colonies. These colonies release medusae, which then participate in sexual reproduction in the water column. The resulting planulae larvae settle back onto surfaces, perpetuating the cycle and leading to high density in favorable coastal environments.

In terms of economic impact, Eirene viridula primarily affects marine aquaculture installations. The main damage occurs when polyps settle on fish cages, nets, and intake pipes. This process is known as biofouling, which creates significant operational difficulties by reducing water flow through nets, leading to oxygen depletion within the cages and promoting the accumulation of organic waste.

The harm is twofold: mechanical and biological. Mechanically, the accumulation of colonies increases the weight and drag on farming equipment, often causing structural damage. Biologically, the medusa stage poses a threat to juvenile fish, as these jellyfish can prey on larvae or irritate the skin and gills of cultured species, thereby increasing the susceptibility of fish to secondary bacterial or parasitic infections.

Control measures are essential for maintaining farm productivity and include:

• Frequent high-pressure washing of nets and submerged gear.
• Application of specialized non-toxic anti-fouling coatings to prevent larval settlement.
• Environmental monitoring to track jellyfish swarms and adjust farming tactics accordingly.
• Improving water circulation management to discourage polyps from settling in stagnant areas.