The common and the rare : relative abundance and the life history drivers of rarity in tropical reef fish

\n \t\t\tA rare species is one with low abundance and/or a small range size. A research approach that prioritises an understanding of the natural causes of rarity and commonness brings attention to those rare species most sensitive to anthropogenic disturbance. This thesis examines the correlations between life history traits and fishing pressure on the rarity and commonness of reef fish and the temporal consistency of these patterns of relative abundance through time. Data were taken from the AIMS Long Term Monitoring Program on the Great Barrier Reef Marine Park (1994 - 2005). The influence of traits (body size, schooling, activity, home range, trophic status, fishing pressure) on patterns of relative abundance was examined using GLMM analysis.Predators with large mean body sizes (lethrinids, lutjanids and serranids) and home ranges were found to be rarest across a range of measures. These species are also the targets of commercial and recreational fisheries. Re-analysis of the dataset after categorization of species as rare or common suggested that mean body size and fishing pressure along with home range, are important determinants of relative abundance. Wide-ranging species also tend to be rare.Relative abundance was strongly negatively correlated with temporal variability. Common species varied little in relative abundance from year to year while rare species varied greatly. Due to this stochastic variation in recruitment, the use of rare species as indicators of reef health may be unreliable.The results of this study suggest that widely ranging rare species may be inadequately conserved using current Marine Protected Areas and ‘no-take’ marine reserves even if the protected area is regarded as of ‘adequate size’ or forms part of an interlinked network of smaller areas. Effective management needs to occur across agencies and national and international borders to support the persistence of rare coral reef species.\n