Suitability of Dual-frequency Identification Sonar (DIDSON) to monitor juvenile fish movement at floodgates

• Published in: New Zealand journal of marine and freshwater research Vol. 45; no. 3; pp. 413 - 422
• Main Authors: Doehring, K, Young, RG, Hay, J, Quarterman, AJ
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 01.09.2011; Taylor & Francis Ltd
• Subjects: barriers; Brackish; DIDSON; Fish; fish behaviour; fish passage; Freshwater; Galaxias; Marine; Radio frequency; Sonar; tide gate; PSE, New Zealand
• ISSN: 0028-8330; 1175-8805
• DOI: 10.1080/00288330.2011.571701

The effects of coastal floodgates on fish distribution are largely unknown. In this study, we used Dual-frequency Identification Sonar (DIDSON) to assess the effect of tidal floodgates on movement of diadromous juvenile galaxiids in a New Zealand estuarine system and test the suitability of DIDSON as a tool for monitoring behaviour of small fish. DIDSON allowed observations of juvenile galaxiid movements over 24 h through contrasting gated and un-gated culverts. More than twice as many fish were recorded passing the un-gated culvert than the gated culvert. Movement occurred during the day and night and was highest at the un-gated culvert just before high tide. By contrast, movement past the gated culvert was highest during low tide, when the gate was open. DIDSON is suitable for discretely observing in situ behaviour of small fish at night or in turbid water and will assist to identify design and operational needs for fish-friendly floodgates.