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Diel variation in stream fish habitat suitability criteria: implications for instream flow assessment

Diel variation in stream fish habitat suitability criteria: implications for instream flow... 1. Habitat suitability criteria that fail to incorporate temporal variability in habitat preferences of stream fish may mis‐represent critical habitat requirements and lead to setting of inappropriate flow targets when used in instream flow assessments. Developing suitability criteria from daytime observations alone relies on the assumption that habitat preferences are constant over the diel cycle. Few studies have tested these assumptions, particularly for small‐bodied, cryptic, benthic species. 2. During summer in two gravel‐bed rivers, bluegill bullies (Gobiomorphus hubbsi), torrentfish (Cheimarrichthys fosteri) and upland bullies (Gobiomorphus breviceps) exhibited strong preferences with respect to water depth, velocity and substratum size. All three species underwent a diel shift in microhabitat preference for at least two of these variables. 3. Microhabitat preferences were generally weaker when fish were active at night; bluegill bullies, upland bullies and especially torrentfish were observed over a broader range of depths, velocities and substratum sizes at night than during the day. Observations of fish in a stream simulator confirmed that bluegill bullies and torrentfish showed a preference for runs at dusk and return to riffles before dawn, but habitat preferences of upland bullies remained static across the diel cycle. 4. Diel microhabitat shifts affected the assessment of flow requirements. Instream habitat analysis of the Waipara River using separate day and night suitability criteria predicted differing amounts of habitat available at a given flow, and the relationships between fish abundance, fish density and flow. The presence of diel microhabitat shifts in stream fishes suggests that instream habitat analyses will produce more effective and defensible flow recommendations when patterns of nocturnal microhabitat preferences are known and critical habitat bottlenecks can be identified. Copyright © 2011 John Wiley & Sons, Ltd. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aquatic Conservation: Marine and Freshwater Ecosystems Wiley

Diel variation in stream fish habitat suitability criteria: implications for instream flow assessment

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References (107)

Publisher
Wiley
Copyright
Copyright © 2011 John Wiley & Sons, Ltd.
ISSN
1052-7613
eISSN
1099-0755
DOI
10.1002/aqc.1166
Publisher site
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Abstract

1. Habitat suitability criteria that fail to incorporate temporal variability in habitat preferences of stream fish may mis‐represent critical habitat requirements and lead to setting of inappropriate flow targets when used in instream flow assessments. Developing suitability criteria from daytime observations alone relies on the assumption that habitat preferences are constant over the diel cycle. Few studies have tested these assumptions, particularly for small‐bodied, cryptic, benthic species. 2. During summer in two gravel‐bed rivers, bluegill bullies (Gobiomorphus hubbsi), torrentfish (Cheimarrichthys fosteri) and upland bullies (Gobiomorphus breviceps) exhibited strong preferences with respect to water depth, velocity and substratum size. All three species underwent a diel shift in microhabitat preference for at least two of these variables. 3. Microhabitat preferences were generally weaker when fish were active at night; bluegill bullies, upland bullies and especially torrentfish were observed over a broader range of depths, velocities and substratum sizes at night than during the day. Observations of fish in a stream simulator confirmed that bluegill bullies and torrentfish showed a preference for runs at dusk and return to riffles before dawn, but habitat preferences of upland bullies remained static across the diel cycle. 4. Diel microhabitat shifts affected the assessment of flow requirements. Instream habitat analysis of the Waipara River using separate day and night suitability criteria predicted differing amounts of habitat available at a given flow, and the relationships between fish abundance, fish density and flow. The presence of diel microhabitat shifts in stream fishes suggests that instream habitat analyses will produce more effective and defensible flow recommendations when patterns of nocturnal microhabitat preferences are known and critical habitat bottlenecks can be identified. Copyright © 2011 John Wiley & Sons, Ltd.

Journal

Aquatic Conservation: Marine and Freshwater Ecosystems – Wiley

Published: Mar 1, 2011

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