Mangrove Clam

Mangrove Clam

Context

ICAR–Central Marine Fisheries Research Institute (CMFRI) achieved a rare global scientific milestone by successfully inducing the breeding of the mangrove clam under captive conditions. This breakthrough at the CMFRI's Mariculture Division aims to revive a rapidly declining estuarine resource and pioneer community-managed aquaculture models integrated with mangrove conservation.

About the Mangrove Clam

• Definition: An ecologically critical bivalve (mud clam) native to the mangrove and estuarine ecosystems of South and Southeast Asia.
• Scientific Name: Geloina erosa (alternatively known as Geloina expansa or Polymesoda erosa).
• Local Names: Popularly known as "Kandal Kakka" in northern Kerala, where it is a valued traditional delicacy.

Habitat and Ecology

• Niche: Inhabits organic-rich, muddy substrates specifically within intertidal mangrove zones.
• Salinity Tolerance: Exhibits remarkable euryhalinity, surviving in environments ranging from brackish water to nearly freshwater.
• Burrowing Behavior: A deep-burrowing, semi-infaunal species. Adults are typically found on the landward side of mangroves, while juveniles are more dependent on tidal presence.

Key Characteristics

• Giant Size: One of the world's largest mud clams, with shells reaching up to 10 cm in width.
• Filter Feeder: Acts as a biological filter, removing suspended particles and plankton, which recycles nutrients and improves water clarity.
• Indicator Species: Its abundance and health serve as indicators of coastal environmental pollution and ecosystem stability.
• Reproductive Trait: Lacks external sexual organs; sexes are identified internally by the color and structure of the gonads (e.g., in specimens under 34 mm).

Breakthrough in Restoration

Historically, farming this species was hindered by a total dependence on wild seed collection. The CMFRI breakthrough has "closed the life cycle" in captivity:

1. Induced Spawning: Scientists triggered spawning in captive broodstock under controlled environmental conditions.
2. Larval Development: Successful rearing through the embryonic and larval stages.
3. Spat Settlement: Reached the "spat" stage (the point where larvae settle and begin to resemble miniature clams) by the 18th day post-spawning.

Significance and Applications

• Sustainable Aquaculture: Paves the way for low-input, climate-resilient estuarine farming that requires minimal infrastructure.
• Ecosystem Ranching: Hatchery-produced seeds can be "ranched" (released) into degraded mangroves to restore natural populations and enhance biodiversity.
• Livelihood Security: Provides a steady, high-protein food source and income for mangrove-dependent coastal communities, particularly in Kerala and India's east coast.
• Conservation: Reduces the extreme harvesting pressure on dwindling wild stocks, which have been depleted by pollution and indiscriminate fishing.

Conclusion

The successful captive breeding of Geloina erosa by CMFRI marks a shift toward extractive aquaculture where the species actually helps clean and restore the environment it is grown in. By standardizing these hatchery protocols, India positions itself as a leader in merging food security with deep-tier mangrove ecosystem restoration.