Context is more important than habitat type in determining use by juvenile fish
Habitat characteristics are often equated with habitat function for animals. However, in heterogeneous landscapes, similar habitat types occur in different environmental contexts. In the marine realm, landscape studies have been confined to particular environments, rather than encompassing entire seascapes, due to incompatible sampling methods required in different situations.
We examined the interactive structuring effects of local habitat characteristics and environmental context on assemblage composition.
We used a single technique—remote underwater video census—to explore the importance of habitat type (biotic structural components, substrate, and depth) and environmental context (marine vs estuarine) in structuring juvenile fish assemblages throughout an entire coastal region. In this model system, a range of structural habitat types were present in both estuarine and marine contexts.
The 1315 video surveys collected show a clear hierarchy in the organisation of juvenile fish communities, with assemblages first distinguished by environmental context, then by habitat type. Marine and estuarine mangroves contained entirely different assemblages, and likewise for rocky reefs and submerged aquatic vegetation. Our results suggest that two functionally different ‘seascape nursery’ types exist at local scales within a single region, defined by their context.
The context of a location can be of greater significance in determining potential habitat function than what habitat-forming biota and substrates are present, and apparently similar habitat types in different contexts may be functionally distinct. These findings have important implications for local-scale management and conservation of juvenile fish habitats, particularly in regard to offsetting and restoration.
KeywordsHabitat Function Nursery role Ecological context Environmental setting Coastal ecosystem Juvenile fish Underwater video
We thank the many people involved in the field sampling and video analysis.
MB, RB, IN and MS contributed to the ideas and design, MB led the field sampling, video analysis, statistical analysis and writing.
This study was funded by the Fisheries Research and Development Corporation, Project No. 2013-046, and the Wet Tropics Management Authority Student Research Grant scheme. RB was partially supported by a fellowship from the Tropical Landscapes Joint Venture between CSIRO and JCU
Compliance with ethical standards
Conflicts of interest
The authors declare that they have no conflict of interest.
This work was conducted with the approval of the JCU Animal Ethics Committee (protocol A2258), and conducted in accordance with DAFF general fisheries permit #168652 and GBRMP permit #CMES63.
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