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Within and between day variability in coral reef fish assemblages: Implications for fish community surveys

Within and between day variability in coral reef fish assemblages: Implications for fish... Coral reef ecosystems are under increasing anthropogenic pressures making it ever more important to monitor changes in fish communities to implement appropriate management. In contrast to long‐term spatial and temporal variation which has been extensively documented, little work has been carried out to identify variability in fish assemblages on short time scales, with few studies testing patterns of fish assemblages between and within days. Here we investigated the diurnal changes in species richness, relative abundance and assemblage composition in a shallow coral reef fish community in Egypt. To do so, a section of coral reef was filmed during the morning (0600 h), midday (1000 and 1400 h) and afternoon (1800 h) over eleven days. Dusk (0600 h) and dawn samples (1800 h) showed higher species richness compared to late morning (1000 h) and mid‐day samples (1400 h) and borderline significantly higher numbers of total individuals, likely associated with feeding activity and predator avoidance. Assemblage composition varied across days and time‐of‐day, showing greater variability during dusk and dawn associated with a transition between day‐time and night‐time assemblages. Our results have implications for designing coral reef fish surveys, emphasising that short‐term changes in fish communities should be considered when designing experiments to monitor fish assemblages over time. Where possible, we suggest increasing replication within sites and time scales or randomising data within a specific time window at all sites, looking to exclude dusk and dawn. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Ichthyology Wiley

Within and between day variability in coral reef fish assemblages: Implications for fish community surveys

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Publisher
Wiley
Copyright
Copyright © 2021 Blackwell Verlag GmbH
ISSN
0175-8659
eISSN
1439-0426
DOI
10.1111/jai.14267
Publisher site
See Article on Publisher Site

Abstract

Coral reef ecosystems are under increasing anthropogenic pressures making it ever more important to monitor changes in fish communities to implement appropriate management. In contrast to long‐term spatial and temporal variation which has been extensively documented, little work has been carried out to identify variability in fish assemblages on short time scales, with few studies testing patterns of fish assemblages between and within days. Here we investigated the diurnal changes in species richness, relative abundance and assemblage composition in a shallow coral reef fish community in Egypt. To do so, a section of coral reef was filmed during the morning (0600 h), midday (1000 and 1400 h) and afternoon (1800 h) over eleven days. Dusk (0600 h) and dawn samples (1800 h) showed higher species richness compared to late morning (1000 h) and mid‐day samples (1400 h) and borderline significantly higher numbers of total individuals, likely associated with feeding activity and predator avoidance. Assemblage composition varied across days and time‐of‐day, showing greater variability during dusk and dawn associated with a transition between day‐time and night‐time assemblages. Our results have implications for designing coral reef fish surveys, emphasising that short‐term changes in fish communities should be considered when designing experiments to monitor fish assemblages over time. Where possible, we suggest increasing replication within sites and time scales or randomising data within a specific time window at all sites, looking to exclude dusk and dawn.

Journal

Journal of Applied IchthyologyWiley

Published: Dec 1, 2021

Keywords: community assemblage; coral; diurnal patterns; monitoring; reef fish; survey; temporal variability

References