Preliminary results of fish population distribution in a Senegalese coastal area with depths less than 15 m, using acoustic methods

¹ ORSTOM - CRODT, BP 2241, Dakar, Sénégal
² ORSTOM, Institut Océanographique, 195 rue St Jacques, 75005 Paris, France

Received: 9 December 1996
Accepted: 29 September 1997

Abstract

In order to manage the fish stock of the Senegal coastal zone it is necessary to carry out direct assessment surveys by acoustic methods. Acoustic surveys were carried out in this region from a sports-fishing boat, using a split-beam echo sounder in vertical mode, in areas with depth less than 15 m. On a short time scale, spatial structure of the fish population remained stable. The average acoustic biomass detected was variable, but we observed a relative stability of target strength distribution of single fish. The use of acoustic methods in these areas of shallow depths, the consequences of escape behaviour of the fish, and sampling strategies are discussed.