The relationship between swimming ability and habitat use in wrasses (Labridae)
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Habitat use is described for a local assemblage of wrasses (family Labridae) at the among-habitat and microhabitat scales of two fringing reef sites at Lizard Island, northern Great Barrier Reef. Visual censuses were used to determine the distribution and abundance of species in five reef habitat zones, and their relative positions within the water column over the reef flat. Based on previous theoretical and empirical analysis of labrid locomotion, mean pectoral fin aspect-ratio residuals were used as an estimate of swimming performance to examine the relationship between swimming ability and habitat use. Among-habitat distributions of inferred swimming ability displayed a distinct dichotomy between shallow and deep reef habitat zones, suggesting a relationship with wave energy. High wave energy (shallow) habitats were characterised by labrids with high (above 0.2) pectoral fin aspect-ratio residuals (fish that use lift-based swimming and achieve high sustained swimming speeds). Although low (below –0.2) aspect-ratio residual species were only in abundance in low wave energy (deeper) habitats, they were also present in low numbers (<7 individuals/100 m2) on the high wave energy reef flat. Water-column use within the reef flat indicated that these low aspect-ratio residual species display a restricted use of the water column and may use substratum complexity and boundary layer effects as a refuge from high levels of water movement. Overall, locomotor morphology was a good predictor of among-habitat and microhabitat use for wrasses at this location. We propose that locomotor performance may be a general force in shaping habitat use by wrasses over these two spatial scales. Some deviations from these general patterns are discussed with regard to the role of behaviour as a mediating factor between morphology and ecology.
KeywordsGreat Barrier Reef Reef Flat Swimming Performance Fringe Reef Swimming Ability
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