Dolphin-Assisted Cast Net Fishing

News: Scientists and conservationists launched an international project on cooperation between wild dolphins and fishers in Ashtamudi Lake, Kerala.

About Dolphin-Assisted Cast Net Fishing

• Dolphin-assisted cast net fishing is a unique, cooperative fishing technique where wild dolphins and human fishermen work together to increase fish catch efficiency.
• Mechanism used
  • The Humpback dolphins rush and zigzag towards mullet (medium-sized, silvery fish), tossing fish into the air and chasing them towards the shore.
  • Traditional cast net fishermen closely watch these movements and cast their nets in front of the advancing dolphins, matching the direction and timing of the chase.
  • This coordinated behaviour creates a form of mutualism, where fishermen get a much better catch of mullet, while dolphins also benefit through more successful foraging on their preferred prey.
  • This mutualism between dolphins and fishermen has been reported from Brazil and Myanmar also.

About Humpback Dolphins

• Type of species:  There are four recognized species of humpback dolphins –
  • Indo-Pacific humpback dolphin (Sousa chinensis)
  • Indian Ocean humpback dolphin (S. plumbea)
  • Atlantic humpback dolphin (S. teuszi)
  • Australian humpback dolphin (S. sahulensis)
• Habitat: They are found in relatively shallow nearshore waters throughout their range which includes most of the coastlines in Australia, Africa and Asia.
  • The Indian Ocean humpback dolphin (Sousa plumbea) is particularly seen along the Kerala coast.
• Conservation Status of Indian Ocean Humpback Dolphin
  • It is considered as ‘Endangered’ by the ICUN.
  • It is within Schedule I of the Wild Life (Protection) Act, 1972.