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SOUND SIGNALS USED INCASTNET FISHING WITHTHE HELP OF IRRAWADDYDOLPHINSTINT TUN aa Biodiversity and Nature ConservationAssociation (BANCA) , No 3/69, SanchaungStreet , Sanchaung , Yangon , Myanmar E-mail:Published online: 13 Apr 2012.

To cite this article: TINT TUN (2008) SOUND SIGNALS USED IN CASTNETFISHING WITH THE HELP OF IRRAWADDY DOLPHINS, Bioacoustics: TheInternational Journal of Animal Sound and its Recording, 17:1-3, 224-226, DOI:10.1080/09524622.2008.9753826

To link to this article: http://dx.doi.org/10.1080/09524622.2008.9753826

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SOUND SIGNALS USED IN CASTNET FISHING WITH THE HELP OF IRRAWADDY DOLPHINS

TINT TUN

Biodiversity and Nature Conservation Association (BANCA), No 3/69, Sanchaung Street, Sanchaung, Yangon, Myanmar. tinttun@gmail.com, tinttun@earthlink.net

INTRODUCTION

Castnet fishing with the help of Irrawaddy dolphins, Orcaella brevirostris, in the upper reaches of the Ayeyawady River (formerly known as Irrawaddy River) is unique to Myanmar. Cooperative fishing with the dolphins has been practiced only in the about 70-km-long Kyaukmyaung and Mingun segment of the Ayeyawady River. It is beneficial for both dolphins and fishermen. Dolphins and fishermen communicate by audio and visual signals during the fishing (Tun 2004, 2005).

CASTNET FISHING WITH THE HELP OF IRRAWADDY DOLPHINS

Dolphins herd the fish and then drive them toward the fishing boat during the fishing. The main strategy of the cooperative fishing technique is that fishermen are positioned at the riverbank or sandbank side while dolphins are positioned at the midwater side of the river in order to trap a shoal of fish against the fishing boats and riverbank or sandbank. The fishing technique has been practiced for more than a century, and it has been passed from generation to generation in both dolphins and fishermen in nature.

SOUND SIGNALS SENT BY CASTNET FISHERMEN

The fishermen try to call the dolphins while the dolphins are passing them. The fishermen start sending sound signals to the dolphins by using a conical wooden pin, castnet, paddle, and mouth so as to attract the passing dolphins to take part in their fishing.

The fishermen make signals by striking a conical wooden pin on a side of their fishing boat, making a guttural sound with their mouth, striking lead weights of the fishing net, or making water splash sounds by throwing the net, chopping the water surface with an edge of paddle blade, or scraping the water surface with a flat surface of the paddle. A signal sent by the fishermen has its meaning as interpreted by the working knowledge of the fishermen.

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A fisherman is sending sound signals with a conical wooden pin while he is following a group of Irrawaddy dolphins.

DISCUSSION

Signals from the fishermen to the dolphins are audio signals, whereas the dolphins send signals to the fishermen by an aerial display of its body parts during the cooperative fishing. These sound signals from castnet fishermen are positive to the fishing, but some anthropogenic noises such as boat noise and banging two iron bars in the water cause a negative affect to the fishing. Tun (2004, 2005) studied the cooperative fishing with the Irrawaddy dolphins but could study the fishery aspects of the fishing. No one has conducted a 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.

ACKNOWLEDGMENTS

This research was supported by the Wildlife Conservation Society (WCS), and the author greatly acknowledges the WCS. The author is

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also grateful to the castnet fishermen from Hsithe, Myitkangyi, and Myayzun villages for their enthusiastic help in this research.

REFERENCES

Tun, T. (2004). Irrawaddy Dolphins in Hsithe-Mandalay Segment of the Ayeyawady River and Cooperative Fishing Between Irrawaddy Dolphin, Orcaella brevirostris, and Castnet 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.

SHIP NOISE AFFECTS ACOUSTIC COMMUNICATION IN THE LUSITANIAN TOAD FISH

RAQUEL 0. VASCONCELOS1•2, M. CLARA P. AMORIM2, AND FRIEDRICH LADICH3

1 Departamento de Biologia Animal e Centro de Biologia Ambiental, Faculdade de Ciencias da Universidade de Lisboa, Bloco C2 Campo Grande, 1749-0161 Lisboa, Portugal. raquel_ vasconcelos@ispa.pt 2 Unidade de Investiga£;iio em Eco-Etologia, I.S.P.A., Rua Jardim do Tabaco 34, 1149-041 Lisboa, Portugal. clara.amorim@ispa.pt 3Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria. friedrich.ladich@univie.ac.at

INTRODUCTION

Ship noise pollution is an increasing environmental problem that might affect the ecology and fitness of aquatic organisms. Most studies on the effects of ship noise have focused on marine mammals or on population assessments for fisheries (Richardson et al. 1995; Vab0 et al. 2002). Only few efforts have been made to describe its harmful effects on fishes, in particular on their acoustic orientation and communication (Amoser et al. 2004; Scholik & Yan 2002; Wysocki et al. 2006).

This study investigates the implications of noise created by a ferryboat on sound detectability in the Lusitanian toadfish, Halobatrachus didactylus. This highly vocal batrachoidid (Dos Santos et al. 2000) occurs in intertidal habitats, which are frequently influenced by human activity.

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