Rough periwinkle

The rough periwinkle (Littorina saxatilis) is a marine gastropod mollusk belonging to the family Littorinidae and the order Littorinimorpha. While it is primarily a component of rocky shore ecosystems, its feeding habits classify it as a pest in the context of commercial seaweed aquaculture and near-shore marine farming operations.

The biological cycle of this species is characterized by ovoviviparity, where the female retains eggs within a brood pouch until they hatch as miniature snails. This strategy provides a distinct advantage in the harsh intertidal environment. The species exhibits significant phenotypic plasticity, allowing it to colonize diverse coastal habitats ranging from exposed cliffs to protected lagoons.

In terms of economic damage, the rough periwinkle acts as a heavy grazer. By using its specialized radula to scrape off algal films and mature thalli, the mollusk significantly reduces the biomass of cultivated seaweed. High-density populations can strip marine farming structures, leading to reduced yields and loss of crop quality during the peak growing seasons.

Symptoms of infestation are easily identified by the appearance of patterned grazing scars on the surfaces of seaweeds or farming substrates. In severe cases, the entire surface of the crop may show signs of intensive scraping, resulting in tissue death and secondary infections of the damaged algal plants by opportunistic pathogens.

Pest management for Littorina saxatilis relies on integrated approaches. Mechanical barriers, such as mesh screens or deterrent coatings on cultivation lines, are widely used to physically exclude the snails. Regular monitoring of snail population densities and timely maintenance of cultivation gear are essential to minimize grazing damage and ensure the productivity of the aquaculture unit.