Use of acoustic telemetry to evaluate fish movement, habitat use, and protection effectiveness of a coral reef no-take zone (NTZ) in Brazil

Abstract

Movement is a key factor that shapes the distribution and structure of fish populations and influences the extent of the benefits provided by conservation and management measures, such as the implementation of marine no-take zones (NTZs). We used visual surveys and acoustic telemetry to investigate density and movement of 2 Brazilian endemic and highly targeted reef fish species inside and outside a coral reef NTZ, and subsequently inferred the effectiveness of the NTZ for protecting these species. To do so, visual surveys were performed on protected and unprotected reefs between 2016 and 2017. Moreover, 20 gray parrotfish Sparisoma axillare and 9 Brazilian snapper Lutjanus alexandrei were tagged with acoustic transmitters and passively monitored from December 2016 to October 2017. For both species, fish densities were significantly higher within the NTZ. Also, both species presented a high residence index over the short term, indicating they were full-time residents of the monitored area until detections were permanently lost. The absence of detections may indicate relocation to deeper reefs, predation, or fishing mortality when fish left the NTZ. Home ranges were small (0.10 to 0.45 km2), and both species presented spatially segregated subgroups within the populations. On average, the percentage of the home ranges within the NTZ was 88% for S. axillare and 95% for L. alexandrei. The results showed that small NTZs that are important to part of the life cycle of a target species are an effective measure to conserve reef fish populations, and also highlight the importance of fisheries management outside NTZs.