Use of encounter data to model spatio-temporal distribution patterns of endangered smalltooth sawfish, Pristis pectinata, in the western Atlantic

1. Sawfishes are among themost threatened fish species globally,with only the smalltooth sawfish (Pristis pectinata) currently regularly observed in the westernAtlantic. TheNational Sawfish EncounterDatabase (NSED) documents reported encounters with sawfishes in the western Atlantic and contains 4945 reports of 8773 individual P. pectinata (1782–2011). 2. Statistical modelling (generalized linear models and generalized additive models) and kernel density analyses were used to (1) identify spatio-temporal patterns among encounter reports, including range reduction in the western Atlantic; (2) determine current distribution to identify areas and time periods where conservation and recovery efforts could be focused; and (3) identify and describe spatio-temporal distribution patterns of large juveniles and adults. 3. Pristis pectinata were found to be year-round residents of Florida but showed relatively consistent spatial and temporal trends by life stage throughout the year. Although the historical range in the western Atlantic included coastal waters from North Carolina to Brazil, the current geographic range of the species was limited to Florida from 2001 through 2011, with occasional reports in neighbouring states, the Bahamas, and Cuba. 4. Seasonally, encounters of all life stages peaked fromMarch through July and annual recruitment of juveniles was apparent during the study period. Spatial hotspots based on increased numbers of encounters of large juveniles (201–340 cm) and adults (>340 cm) were identified in southern Charlotte Harbor, the Ten Thousand Islands, Florida Bay, theAtlantic side of the FloridaKeys, and off St. Lucie in south-east Florida. The analyses presented herein provide evidence of range reduction in the western Atlantic, provide an important tool for resource managers to focus research, monitoring, and conservation efforts, and may provide a framework to model and predict habitat use of other species.