Abstract
Nonreef habitats such as mangroves, seagrass, and macroalgal beds are important for foraging, spawning, and as nursery habitat for some coral reef fishes. The spatial configuration of nonreef habitats adjacent to coral reefs can therefore have a substantial influence on the distribution and composition of reef fish. We investigate how different habitats in a tropical seascape in the Philippines influence the presence, density, and biomass of coral reef fishes to understand the relative importance of different habitats across various spatial scales. A detailed seascape map generated from satellite imagery was combined with field surveys of fish and benthic habitat on coral reefs. We then compared the relative importance of local reef (within coral reef) and adjacent habitat (habitats in the surrounding seascape) variables for coral reef fishes. Overall, adjacent habitat variables were as important as local reef variables in explaining reef fish density and biomass, despite being fewer in number in final models. For adult and juvenile wrasses (Labridae), and juveniles of some parrotfish taxa (Chlorurus), adjacent habitat was more important in explaining fish density and biomass. Notably, wrasses were positively influenced by the amount of sand and macroalgae in the adjacent seascape. Adjacent habitat metrics with the highest relative importance were sand (positive), macroalgae (positive), and mangrove habitats (negative), and fish responses to these metrics were consistent across fish groups evaluated. The 500‐m spatial scale was selected most often in models for seascape variables. Local coral reef variables with the greatest importance were percent cover of live coral (positive), sand (negative), and macroalgae (mixed). Incorporating spatial metrics that describe the surrounding seascape will capture more holistic patterns of fish–habitat relationships on reefs. This is important in regions where protection of reef fish habitat is an integral part of fisheries management but where protection of nonreef habitats is often overlooked.
Highlights
Fishes use multiple habitats for a variety of ecological reasons
Local reef variables were selected most often in models, the mean relative importance for influential variables was similar between adjacent habitat and local reef
Other research comparing the influence of local coral reef and adjacent habitats on coral reef fishes has found that seascape-scale habitat can be more important than local reef habitat (Henderson et al, 2017; Kendall et al, 2011; Knudby et al, 2011; Olds, et al, 2012; Yeager et al, 2011)
Summary
Fishes use multiple habitats for a variety of ecological reasons. In tropical coral reef ecosystems, nonreef habitats include, but are not limited to mangrove forests, seagrass meadows, and macroalgal beds. Remote sensing technology and spatial analysis software have allowed for the development of marine habitat maps that describe diverse seascapes in high resolution across large spatial extents (Hedley et al, 2016; Kendall & Miller, 2008; Roelfsema et al, 2018) This provides users with the flexibility to explore species–habitat relationships across multiple spatial scales, at spatial resolutions that are useful for ecological studies. In the Philippines, coral reefs are often adjacent to or near large areas of seagrass beds, macroalgal beds, and/or mangrove stands We use this system to explore how spatial connectivity of multiple habitats in a seascape affects coral reef fish. We aim to understand fish–habitat relationships in a diverse model seascape, focusing on coral reef fishes to explore 1. the relative importance of local scale coral reef habitat and adjacent nonreef habitats on fish species presence, density, and biomass, and 2. which nonreef habitats and spatial connectivity metrics are the most important
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