Foraging microhabitat preferences of invertivorous fishes within tropical macroalgal meadows: identification of canopy specialists

Abstract

Invertivorous fishes are key middle-order consumers that connect energy flows across different trophic levels. However, the potential for distinct functional roles to exist within this trophic guild has not been satisfactorily explored to date, meaning that current assessments of ecosystem resilience are likely to over-estimate the level of functional redundancy within a given invertivorous fish assembly. Our study examined the foraging behaviour and microhabitat preferences of invertivorous fish communities within the productive canopy macroalgal meadows of Ningaloo Marine Park, Western Australia. Our aim was to identify foraging specialisations that could yield distinct functional roles for species belonging to the guild. We found that invertivorous fishes at this location were chiefly represented by species belonging to the Labridae, Lethrinidae and Mullidae families. Individual species demonstrated strong preferences for foraging within specific microhabitat types, suggesting that the guild can be grouped into three categories of foraging specialists: ‘canopy forager’, ‘generalist’ and ‘abiotic forager’. Our results highlight subtle niche partitioning of foraging microhabitats within the trophic guild of invertivorous fishes associated with tropical macroalgal meadows. Moreover, this partitioning is consistent across seasons, despite significant fluctuations in canopy structure and biomass. The resulting refinement of foraging specialisations allows us to identify the functional roles of invertivorous fishes and afford greater protection to individual species that might otherwise be considered functionally redundant. Our results will help to inform knowledge of the functional impact of particular species and their ecological specialisations and improve our understanding of trophic flows in marine food webs for appropriate management and conservation.