Sponge crab

Dromia vulgaris, commonly known as the sponge crab, is a species of decapod crustacean belonging to the family Dromiidae. It is strictly a marine organism and does not pose a threat to terrestrial agriculture. However, in the context of marine aquaculture, it is recognized as a pest that can cause economic losses in shellfish farming operations.

The biology of this species is characterized by its symbiotic relationship with sponges or ascidians, which it carries on its back for camouflage. Development involves larval stages that drift in the water column before settling on the seabed. Adults are nocturnal predators, showing significant adaptability to various marine environments, including rocky reefs and artificial aquaculture structures.

The pest potential of the sponge crab lies in its feeding behavior directed toward farmed bivalves. They utilize their strong chelae to manipulate and crush the shells of mussels and oysters. In areas with high concentrations of shellfish collectors, the presence of Dromia vulgaris can lead to substantial reduction in marketable yields, particularly during the growth phases of the mollusks.

Damage symptoms include fractured shells and empty valves found within the culture collectors. Unlike fish predation, which often targets soft tissue, sponge crabs break down the protective shell, often leading to the complete consumption of the animal inside. This damage is particularly problematic in systems where shellfish are grown in proximity to the natural habitat of these crabs.

Management strategies focus on physical exclusion rather than chemical eradication to maintain ecological balance. Implementation of specialized protective netting is the most effective approach to prevent access to cultivation areas. Regular underwater surveys and manual removal of crabs from structures remain the standard practices for mitigating damages in commercial mollusk farms.