Abstract
The smalltooth sawfish (Pristis pectinata) is an elasmobranch and one of five sawfish species. The distribution of the United States population of smalltooth sawfish is now limited to southwest and south Florida. In 2009, the Charlotte Harbor estuarine system, which includes the Peace River, was listed as critical habitat for juveniles of this species. Considering their endangered status, it is important to monitor these fish to understand what could be done to facilitate protection of the population. Previous research had identified the lower Peace River as the northernmost occupied nursery, and diel movements suggested differences in habitat use associated with both sides of the river. Because use of the northern shoreline has been relatively well documented, this study characterizes the habitat use of the southern shoreline using a series of nine, time-synchronized acoustic receivers. Twenty individuals were tagged and continuously tracked using passive acoustic monitoring in the study area from 27 May–26 October 2016. Eleven sawfish were detected by receivers on the southern shoreline, and six individuals used habitats there extensively; these position estimates were sorted into three habitat types: deep (>1 m), shallow (≤1 m), and human-built oyster reefs along the shoreline. In addition, diel movement patterns and swimming speeds were investigated for these six individuals. Collectively, results indicated that sawfish regularly crossed the river at night. Timing of river crossing was not influenced by tidal cycle. All sawfish tended to be detected in shallow water including oyster habitats. One age-1 individual exhibited reduced swimming speeds during the day, and two young-of-the-year individuals were more active at night. These data will support management decisions about this unique nursery and has implications for recovery planning in other remaining nurseries.
