Long-wristed hermit crab

The long-wristed hermit crab (Pagurus longicarpus) is a crustacean belonging to the order Decapoda and the family Paguridae. While naturally occurring in marine environments, this species is identified as an opportunistic pest in specific aquaculture settings, particularly where shellfish farming operations are conducted within their native or introduced range.

These crustaceans are predominantly found in estuarine and coastal waters along the Atlantic coast, favoring muddy or sandy substrates. In an agricultural and aquaculture context, their presence becomes a concern when they congregate near shellfish beds or submerged cages, posing a threat to the viability of the cultivated stock through resource competition and predation.

The biology of Pagurus longicarpus is characterized by a specialized lifecycle involving multiple larval stages that disperse through water currents. Once they reach the megalopa stage, they settle on the substrate and seek empty gastropod shells for shelter, a behavior that dictates their spatial distribution and seasonal abundance patterns in farming areas.

The primary economic impact is attributed to the damage inflicted on juvenile bivalves. By penetrating protective enclosures or congregating in nursery areas, these crabs can disrupt the feeding and growth cycles of shellfish. Their opportunistic scavenging and predatory habits lead to significant losses in biomass, necessitating vigilant management to protect the harvest.

Management and control strategies include several proactive measures:

• Installation of fine-mesh barriers to prevent crustacean entry into cultivation cages.
• Regular manual inspection and cleaning of aquaculture equipment to remove encroaching crabs.
• Deployment of specialized bait traps to reduce the population density around sensitive shellfish beds.
• Strategic site selection to avoid areas with historically high hermit crab density during critical larval settlement phases.