Shrimp farms drive wild harvest of India's

India's shrimp hatcheries are consuming vast quantities of wild polychaete worms, also known as bristle worms, as live feed. Experts warn this unregulated harvest threatens natural stocks and the benthic ecosystems these worms inhabit.

According to Perumal Murugesan, an associate professor at Annamalai University, over 200 registered shrimp hatcheries on India's east coast require an estimated 400 kilograms of the worms every day. Hatchery operators prefer them due to their rich polyunsaturated fatty acid content, which is proven to increase shrimp spawning rates.

Ecological role and pollution indicators

Polychaete worms are a diverse group of marine annelids found in almost all marine habitats. They play crucial ecological roles. As detritivores, they break down organic matter and help transport and redistribute oxygen in sediments. They are also a major food source for other marine organisms.

Their sensitivity to environmental stress makes them valuable bioindicators. "Changes in their abundance and community composition can reflect changes in sediment quality and other environmental stresses," said Sanitha Sivadas, a scientist at the National Centre for Coastal Research. Moumita Bhowmik, a PhD scholar, is studying polychaetes in the polluted mudflats of the Gulf of Khambhat. She notes they are perfect model systems for studying adaptation to pollution and could even be valuable for future pollution remediation strategies.

The cost of wild harvesting

A large network has emerged to meet the shrimp industry's demand. On the Tamil Nadu coast, members of the Irular tribal community handpick the worms from intertidal mudflats. Murugesan states they receive only 500-800 Indian rupees per kilogram. By the time the worms reach a hatchery, the price has skyrocketed to 3,500-4,000 rupees per kg.

Murugesan is concerned that continued wild collection could deplete natural stocks. He emphasizes the need for a balance. "We have to see to it that the natural environment is protected, and their livelihood is also protected." he said. Researchers are exploring aquaculture as a sustainable alternative. Murugesan's team has patented a technology for farming the native Perinereis nuntia species.

Underexplored diversity

Despite their importance, polychaete worms in Indian waters remain poorly documented and understudied. Sivadas notes that the current recorded diversity represents only a part of the actual diversity. A 2020 checklist she co-authored compiled 727 marine annelid species from Indian waters, but about 25% of those records were considered questionable.

Taxonomic work is sparse. Between 2001 and 2019, researchers reported only eight new polychaete records for India. Sivadas calls for more support for taxonomists, calling taxonomy the foundation of biodiversity research. She also advocates for better exploration of poorly studied regions and habitats, as even previously surveyed areas can reveal overlooked species.