Fish movement from nursery bays to coral reefs: a matter of size?

Movement of fish across habitat boundaries provides an important link between marine ecosystems such as mangroves, seagrass beds, and coral reefs, yet direct evidence of ontogenetic movements across these systems is scarce. We used acoustic telemetry to investigate movement patterns between bay nursery habitats and adult reef habitats by a common Caribbean fish (Lutjanus apodus). We hypothesized that juvenile fish residing in their nurseries increase their home range as they grow and eventually include coral reefs in their activity range before their permanent migration to this adult habitat. Tagged fish were detected by underwater receivers for a period up to 12 months and a clear diel pattern was visible with most detections occurring during nighttime. Bay-to-reef movements were undertaken by fish that were larger than fish that were only detected in the bay. Stable isotope values of fin tissue from fish that showed reef-ward movements were similar to those of fish remaining in the bay, indicating that these movements were likely exploratory behavior as opposed to repeated feeding excursions. Understanding cross-habitat ontogenetic movements is essential for identification of ecologically relevant spatial scales for management of coastal fish populations.