Integrated Catchment Management


(Note: this information comes from Cawthron Report 1260 - see Publications for more details)

Methods to observe fish behaviour at structures and streams and the ability to count fish numbers passing these structures have been limited. Dual Frequency Identification Sonar (DIDSON) is a rapid method of determining the presence of a target organism or object in water regardless of water clarity.

The camera was trialled at several localities in and around Nelson where tidal gate structures exist, including the Motueka River.

Map of DIDSON trial site


The approach was to run the DIDSON for approximately 24 hours or to cover 2 tidal cycles and to collect sufficient imagery to demonstrate the effectiveness of the method and the behaviour of the fish in relation to tide gate operation.

DIDSON scan and whitebait near tidal gate

For more information contact Rowan Strickland or Roger Young.