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Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and environmental controls on nanga (Galaxias maculatus) spawning grounds

Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and... Galaxias maculatus is a declining amphidromous fish that supports New Zealands culturally important whitebait fisheries targeting the migratory juvenile stage. Spawning ground protection and rehabilitation is required to reverse historical degradation and improve fisheries prospects alongside conservation goals. Although spawning habitat has been characterised in tidal rivers, there has been no previous study of spawning in non-tidal rivermouths that are open to the sea. We assessed seven non-tidal rivers over 4 months using census surveys to quantify spawning activity, identify environmental cues, and characterise fundamental aspects of the biogeography of spawning grounds. Results include the identification of compact spawning reaches near the rivermouths. Spawning events were triggered by periods of elevated water levels that were often of very short duration, suggesting that potential lunar cues were less important, and that rapid fish movements had likely occurred within the catchment prior to spawning events. Spawning grounds exhibited consistent vertical structuring above typical low-flow levels, with associated horizontal translation away from the river channel leading to increased exposure to anthropogenic stressors and associated management implications for protecting the areas concerned. These consistent patterns provide a sound basis for advancing protective management at non-tidal rivermouths. Attention to flood management, vegetation control, and bankside recreational activities is needed and may be assisted by elucidating the biogeography of spawning grounds. The identification of rapid responses to environmental cues deserves further research to assess floodplain connectivity aspects that enable fish movements in ephemeral flowpaths, and as a confounding factor in commonly used fish survey techniques. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Pacific Conservation Biology CSIRO Publishing

Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and environmental controls on nanga (Galaxias maculatus) spawning grounds

Orchard, Shane; Schiel, David R.
Pacific Conservation Biology , Volume 28 (2): 14 – May 11, 2021
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Publisher
CSIRO Publishing
Copyright
Copyright © The Author(s). Published by CSIRO Publishing
ISSN
1038-2097
eISSN
2204-4604
DOI
10.1071/PC21004
Publisher site
See Article on Publisher Site

Abstract

Galaxias maculatus is a declining amphidromous fish that supports New Zealands culturally important whitebait fisheries targeting the migratory juvenile stage. Spawning ground protection and rehabilitation is required to reverse historical degradation and improve fisheries prospects alongside conservation goals. Although spawning habitat has been characterised in tidal rivers, there has been no previous study of spawning in non-tidal rivermouths that are open to the sea. We assessed seven non-tidal rivers over 4 months using census surveys to quantify spawning activity, identify environmental cues, and characterise fundamental aspects of the biogeography of spawning grounds. Results include the identification of compact spawning reaches near the rivermouths. Spawning events were triggered by periods of elevated water levels that were often of very short duration, suggesting that potential lunar cues were less important, and that rapid fish movements had likely occurred within the catchment prior to spawning events. Spawning grounds exhibited consistent vertical structuring above typical low-flow levels, with associated horizontal translation away from the river channel leading to increased exposure to anthropogenic stressors and associated management implications for protecting the areas concerned. These consistent patterns provide a sound basis for advancing protective management at non-tidal rivermouths. Attention to flood management, vegetation control, and bankside recreational activities is needed and may be assisted by elucidating the biogeography of spawning grounds. The identification of rapid responses to environmental cues deserves further research to assess floodplain connectivity aspects that enable fish movements in ephemeral flowpaths, and as a confounding factor in commonly used fish survey techniques.

Journal

Pacific Conservation Biology – CSIRO Publishing

Published: May 11, 2021

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