The Replenishment of Popula Nons of Coral Reef Fishes, Recruitment Surveys, and the Problems of Variability Manifest on Multiple Scales

Unpredictable recruitment of juveniles is the greatest obstacle presently limiting descriptions of the population dynamics of benthic stocks of coral reef fishes and preventing the development of management strategies for these animals. Some workers have dismissed this problem as one only of scale on the assumption that most ecological studies are performed over spatial scales which emphasize variation and are mismatched to the needs of management. The effect of analytical scale was investigated by examining local, regional and geographic patterns of recruitment for one common damselfish, Pomacentrus wardi. These data were collected with several independent surveys of juvenile densities on the Great Barrier Reef, Australia. Collectively, the surveys spanned spatial scales from meters to >1,000 km and temporal scales from days to almost a decade. Spatial patterns were most consistent when aggregate statistics from more than one coral reef were involved. In contrast, coral reefs and parts thereof showed complex patterns of variation which suggest that pre-settlement fish are aggregated in the pelagic environment at two spatial scales: micro-scale patches of a few meters and meso-scale patches of tens of kilometers.