Human–dolphin cooperative fishing in Ashtamudi lake

Ashtamudi Lake in Kerala is home to one of the world’s few remaining examples of active human–wildlife cooperative foraging.

Collaboration occurs between artisanal fishers and Indo-Pacific humpback dolphins (Sousa plumbea).

Indo-Pacific humpback dolphin (Sousa plumbea)

• Found in shallow coastal and estuarine ecosystems.

• Known for social intelligence and ability to engage in complex cooperative behaviour.

Dolphins herd fish into shallow waters near the shoreline.

They signal fishers through tail-slaps or rolling movements.

Fishers cast nets immediately upon receiving these cues.

Mutual benefit:

• Fishers get a higher catch.

• Dolphins feed on scattered fish after net deployment.

Fishers possess knowledge of dolphin behaviour.

Cooperation is not accidental but a culturally maintained practice on both sides.

Indo-Pacific humpback dolphin (Sousa plumbea) is a coastal marine mammal found in the Indian Ocean and western Pacific region.

Known for distinctive hump-like dorsal area and high levels of social intelligence.

Often associated with shallow, turbid waters near river mouths, estuaries, lagoons, and mangrove ecosystems.

Genus: Sousa

Species: plumbea

Commonly referred to as the Indian Ocean humpback dolphin.

Earlier considered part of Sousa chinensis, but later classified as a distinct species.

Coastal waters of:

• East Africa to the Bay of Bengal

• Arabian Sea

• Coast of India (both east and west coasts)

• Sri Lanka and Maldives

Prefers water depths less than 30 metres.

Shallow coastal waters

Estuaries and river mouths

Lagoons and mangrove belts

Turbid waters with high productivity

Brackish ecosystems like Ashtamudi Lake, Kerala

Length: 2–2.8 metres.

Colour: Light grey to dark grey; juveniles lighter.

Distinctive hump below the dorsal fin.

Highly social and intelligent species.

Display complex behaviours such as:

• Cooperative hunting

• Tool-like use of group coordination

• Acoustic communication

• Synchronised foraging strategies

Feeds on fish, crustaceans, and cephalopods.

Often hunts in turbid, shallow waters where fish density is high.

IUCN status: Near Threatened.

CITES Appendix I – highest level of protection.

Indian Wildlife (Protection) Act: Schedule II species.

Coastal habitat loss and degradation

Noise pollution (ports, shipping, dredging)

Overfishing and prey depletion

Bycatch in fishing nets

Pollution: heavy metals, industrial effluents, plastics

Climate change impacts on coastal ecosystems

Habitat-based conservation in lagoons, estuaries, mangroves

Reduction of bycatch through gear modification

Marine protected areas and coastal zone regulation

Community engagement for sustainable fishing

Research on behaviour, migration, and population dynamics

Kerala

Goa

Maharashtra

Odisha

West Bengal

Gujarat (Gulf of Kutch and Gulf of Khambhat)