Abstract
Habitat use and movements of juvenile (<3 yr old) Critically Endangered smalltooth sawfish Pristis pectinata were studied in the Peace River in southwest Florida to estimate the size of a known nursery hotspot (high-use area). A total of 23 smalltooth sawfish were tagged during the peak recruitment period of April and May 2014 and were tracked until the end of September 2014 using passive acoustic monitoring. Active tracking was used to estimate positions of individuals relative to the shoreline and major habitat types. During the day, sawfish <1500 mm stretched total length (STL; n=11), representing <1 year old fish, and those measuring 1504 to 1881 mm STL (n=12), representing >1-year-old fish (1–3 years old), remained along the northern shoreline of the river in a protected cove. The younger age class remained closer (<25 m) to red mangrove-dominated shorelines than did the older age class. At night, both age classes moved away from the shoreline and away from the protected cove; the older individuals made the longest excursions (~5 km), toward the southern shoreline of the river. The discovery of these regular diel movements has led to the expansion of the boundaries of the single recognized nursery hotspot in the Peace River, which was previously defined solely by daytime catch data. These data are crucial for aiding the conservation of this Critically Endangered species and adding an extra layer of protection within its federally-designated Critical Habitat.