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Sawfishes are among the most threatened fish species globally, with only the smalltooth sawfish (Pristis pectinata) currently regularly observed in the western Atlantic. The National Sawfish Encounter Database (NSED) documents reported encounters with sawfishes in the western Atlantic and contains 4945 reports of 8773 individual P. pectinata (1782–2011).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.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.Seasonally, encounters of all life stages peaked from March 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, the Atlantic side of the Florida Keys, 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. Copyright © 2014 John Wiley & Sons, Ltd.

Background The evolutionary processes that shape patterns of species richness in marine ecosystems are complex and may differ between organismal groups. There has been considerable interest in understanding the evolutionary processes that led to marine species richness being concentrated in specific geographical locations. In this study we focus on the evolutionary history of a group of small-to-medium sized sharks known as carpet sharks. While a few carpet shark species are widespread, the majority of carpet shark species richness is contained within a biodiversity hotspot at the boundary of the Indian and Pacific oceans. We address the significance of this biodiversity hotspot in carpet shark evolution and speciation by leveraging a rich fossil record and molecular phylogenetics to examine the prehistoric distribution of carpet sharks. Results We find that carpet sharks species richness was greatest in shallow seas connected to the Atlantic Ocean during the Late Cretaceous, but that there was a subsequent loss of biodiversity in Atlantic waters. Fossil evidence from sites in close geographic proximity to the current center of carpet shark diversity are generally restricted to younger geologic strata. Conclusions From this data we conclude that (1) center of carpet shark biodiversity has shifted during the last 100 million years, (2) carpet sharks have repeatedly dispersed to nascent habitat (including to their current center of diversity), and (3) the current center of carpet shark biodiversity conserves lineages that have been extirpated from this prehistoric range and is a source of new carpet shark species. Our findings provide insights into the roles of marine biodiversity hotspots for higher-tropic level predators and the methods applied here can be used for additional studies of shark evolution.

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