Lear et al.: Fine-scale behavior and habitat use of Pristis pectinata 
355 
Depth (m) 
Hour of day 
Hour of day 
Figure 5 
Patterns of activity of smalltooth sawfish (Pristis pecti¬ 
nata) in the Peace River, Florida, with percentage of time 
fish were active in relation to (A) depth and (B) time of 
day and tidal period, from data analysis conducted with 
generalized additive mixed models (GAMMs). The lines 
for first ebb and second flood are essentially the same and 
overlay each other. (C) The relationship of the number of 
burst events of smalltooth sawfish with time of day, the 
only predictor of the burst frequency included in the best- 
fit GAMM. Dashed lines in panels A and C show standard 
error of the GAMM smoother; standard errors are not 
shown in panel B in the interest of clarity. Data used in 
the models were collected from acceleration data loggers 
deployed on smalltooth sawfish caught and tagged in the 
Peace River between May 2014 and November 2015. 
sawfish may travel or wait near the bottom and quickly 
burst upward into the water column, potentially in pursuit 
of teleost fishes, their primary prey (Poulakis et al., 2017). 
Other burst events were not accompanied by predictable 
changes in depth, instead occurring at relatively constant 
depths, presumably on or near the bottom. We hypothesize 
that these events indicate benthic prey capture or pinning 
behavior, in which smalltooth sawfish pin prey, such as 
rays, on the substrate (Poulakis et al., 2017), using their 
rostrum until they can maneuver prey into their mouths 
(Wueringer et al., 2012). These high-acceleration amplitude 
Depth (m) 
Figure 6 
Frequency of use of depths by smalltooth sawfish (Pristis 
pectinata), by age class, in the Peace River, Florida, from 
May 2014 through November 2015. Depth values are 
mean depths (in paired bins of 0.25 m) from all hours of 
deployment of acceleration data loggers. The age classes 
were young of the year (YOY, <1.5 m stretch total length 
[STL]) and individuals >age 1 (>1.5 m STL). The young¬ 
est individuals used shallower depths than those used by 
older individuals, and they did not occur below 1.5 m; older 
individuals made occasional excusions up to 3.6 m. 
signals could also represent sawfish avoiding predation by 
bull sharks (Carcharhinus leucas), which are one of the 
main predators of smalltooth sawfish in Florida (Brame 
et al., 2019). However, predation pressure on smalltooth 
sawfish in the Peace River is considered low because of the 
divergent salinity affinities between bull sharks and small¬ 
tooth sawfish (Poulakis et al., 2011). 
Environmental drivers of activity and foraging 
Temperature and time of day were the most influential 
drivers of activity, with both factors included in the top-5 
candidate models for activity. The highest activity rates 
were observed at higher water temperatures and during 
evening and night hours. That activity increased with 
water temperature was not unexpected because ectother- 
mic animals, including elasmobranchs, often increase 
activity as temperatures increase and, therefore, muscle 
performance capacity and metabolic needs increase 
(Halsey et al., 2015; Lear et al., 2017, 2019). The crepus¬ 
cular and nocturnal activity observed in the smalltooth 
sawfish is also similar to that observed in many elasmo¬ 
branchs (reviewed by Hammerschlag et al., 2017), activity 
that is often attributed to the exceptional sensory capabil¬ 
ities of elasmobranchs (Hueter et al., 2004). 
Similar crepuscular and nocturnal activity has been 
observed in other sawfish species (Gleiss et al., 2017; 
Whitty et al., 2017), and these findings confirm hypothe¬ 
ses of diel activity patterns in juvenile smalltooth saw¬ 
fish formed during previous studies that included passive 
and active acoustic monitoring (Hollensead et al., 2016; 
