SOUND SIGNALS USED IN CASTNET FISHING WITH THE HELP OF IRRAWADDY DOLPHINS Tint Tun Biodiversity and Nature Conservation Association, Union of Myanmar.

Introduction Castnet fishing with the help of Irrawaddy dolphins, Orcaella brevirostris, in upper reaches of the Ayeyawady River (previously known as Irrawaddy River) is a unique

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Sound Signals Sent by Castnet Fishermen

Castnet Fishing with the Help of Irrawaddy Dolphins The main strategy of cooperative fishing technique with Irrawaddy dolphin is: fishermen are positioned at a river-bank or sand-bank side while dolphins are being positioned at mid-water side of the river in order to trap a shoal of fish against the

1.

Signal

Series of striking sound

Making

This sound, trat tat tat tat,

Fishermen make sound signals during the attracting and fishing phases but they

like a series of shortpulsed decrescendo drum rolls, is made by striking

do not make any signals in terminating phase. Fishermen send audio signals of one vocal and five non-vocal sounds in

on a side of boat with a conical wooden pin.

air and water medium respectively and dolphins show signals to the fishermen

fishing boat(s) and river/sand bank. Castnet fishing with the help of the Irrawaddy dolphins can be divisible into three phases: Attracting, Fishing and Terminating.

of Myanmar (previously known as Burma). Cooperative fishing with the

1.Attracting Fishermen follow the dolphins and make

dolphins has been practiced only in about 75km long Kyaukmyaung

'call' sounds with a conical wooden pin on their way. They make signals with leadweight of the castnet and guttural sound

and Mandalay segment of

with their mouth when the dolphins are

the Ayeyawady River. The fishing technique has been practiced for more than a

near to them. They also throw a few casts to let the dolphins know that they are castnet fishermen and where they are fishing.

century and it has been passing from generation to generation in both dolphins and fishermen in nature. Dolphins and fishermen communicate each other by audio and visual signals during the fishing. (Tun, 2004, 2005).

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2. Fishing The dolphins slaps the water surface with its fluke, like lob-tailing, and it means that they engage in fishing and they start to herd fishes. Then, they drive the fishes Dolphin drives fishes towards the towards a fishing boat by a forceful lateral fishing boat at a net-throw distance from the boat. wave of halfway-submerged fluke in the direction of a fishing boat at a net-throw distance. It is the time to throw the net. The fishermen keep sending signals made with mouth and paddle so as to keep attracting dolphins and continue their fishing with the Kyauk Myaung help of the dolphins. 3. Terminating Cooperative fishing comes to an end when fishermen or dolphins terminate the fishing. In this phase, dolphins show no more interest in cooperative fishing by neglecting the fishermen’s signals and swim away or fishermen stop sending signals. However, other fishing boats which wants to continue or conduct cooperative fishing will make 'call' signals to keep dolphins staying with them and to help them.

2.

by its body displays. Except for a conical wooden pin of about 30 cm. in length as a

Signal

Guttural sound

Making

Fishermen make this

special instrument, all the rest instruments are those used in their fishing.

sound (Karururu) by his mouth. Meaning Come and help. We are fishing and we are ready.

Fishermen start sending sound signals when they sight dolphins. They make signals by striking a conical wooden pin on a side of their fishing boat or making guttural sound with their mouth or

3.

Signal

Striking sounds

Making

Striking on a side of boat or on the floor of boat with lead-weights attached at the fringe of a cast net.

Meaning Come and help. We are castnet fishermen.

4.

Signal

Splash sound (net throwing)

Making

Throwing cast-net.

Meaning We are castnet fishermen and we are fishing here.

striking led-weights of the fishing net or making water splash sounds by throwing net or chopping water surface with an edge of paddle blade or scrapping water surface with a flat surface of the paddle.

Acknowledgements This research was supported by Wildlife Conservation Society (WCS). The author is grateful to WCS and the castnet fishermen from Hsithe, Myitkangyi and Myayzun villages for their enthusiastic help in this research.

References Tun, T. (2004). Irrawaddy Dolphins in HsitheMandalay Segment of the Ayeyawady River and Cooperative Fishing Between Irrawaddy Dolphin,

5.

Signal

Splash sound (chopping)

Making

Water surface is chopped with an edge of paddle’s flat.

Meaning Not ready to throw yet.

Discussion Signals from fishermen to the dolphins are audio signals whereas dolphins send signals to the fishermen by aerial display of its body parts during the cooperative fishing. These sound signals from castnet fishermen are positive to the fishing but some Fishing with the help of Irrawaddy dolphins can only be found anthropogenic noises such as boat noise and in Kyauk Myaung and Mandalay segment of the Ayeyawady banging two iron bars in the water cause negative River (previously known as Irrawaddy River). affect to the fishing. Tun (2004, 2005) studied the cooperative fishing with the Irrawaddy dolphins but he could study fishery aspects of the fishing. However,

Meaning Come and help.

Show up where you are.

Orcaella brevirostris, and Cast-net Fishermen in Myanmar. A report submitted to the Wildlife Conservation Society. Tun, T. (2005). Castnet Fisheries in Cooperation with Irrawaddy Dolphins (Ayeyawady Dolphins) at Hsithe, Myitkangyi and Myayzun Villages, Mandalay Division, in Myanmar. A report submitted to the Wildlife Conservation Society.

MANDALAY

6.

Signal

Splash sound (scrapping)

Making

Water surface is scraped with a flat end of a paddle to make a splash sound.

Meaning Swim along with us because we do not like the

communication among the dolphins may also be made while they are taking part in the fishing. No one has been conducted scientific acoustics study on the cooperative fishing, especially, signals sent among the dolphins, so far. Furthermore, any bioacoustics study on marine mammals has not been done in Myanmar water and, therefore, it is a great challenge and opportunity for the bioacoustic scientists.

current location to throw net. Suspend your fluke strike as we are moving to a desired location.

Dolphins feed on the fishes which are in panic while fisherman is hauling his net.

A cooperative fishing event observed at the Hsithe village 1. A group of dolphins swam from downstream to upstream; passed the village near sand bank side. 2. Fishermen sighted the dolphins; left their village; followed and called the dolphins on their way. 3. Dolphins turned to downstream. Fishermen had been calling dolphins. 4. Dolphins engaged castnet fishing. 5. Fishermen stopped fishing with the dolphins and let them swam as they like; dolphins swam downstream.

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