Lear et al.: Fine-scale behavior and habitat use of Pristispectinate 
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depth distributions of YOY and older fish, with fish age 1 
and older venturing deeper than YOY This ontogenetic 
shift in depth use has been reported in a number of previous 
studies of both smalltooth and largetooth sawfish, indicat¬ 
ing that YOY individuals stayed in shallow areas close to 
shore while larger fish that have less predation risk ven¬ 
tured farther from shorelines to use deeper habitats (Whitty 
et al., 2009; Simpfendorfer et al., 2010; Huston et al., 2017). 
Habitat use and foraging ecology 
The patterns of activity and putative foraging effort, com¬ 
bined with knowledge about depth and habitat use, reveal 
important insights into the foraging ecology of these ani¬ 
mals. Increased activity and putative foraging of small¬ 
tooth sawfish was tied to habitats in the main stem of the 
Peace River, and refuging was more common in shallow 
habitats. This pattern is the opposite of that observed in 
the morphologically similar largetooth sawfish (Gleiss 
et al., 2017; Whitty et al., 2017). Largetooth sawfish stud¬ 
ied in the Fitzroy River, Australia, are thought to use 
shallow sandbar habitats, which are generally devoid of 
woody debris, to forage because of increased abundance 
of prey, and snags and woody debris in the deeper areas of 
the river offer better refuging habitats from crocodilians, 
which are common along shorelines (Morgan et al., 2017; 
Whitty et al., 2017). Although foraging in shallow habitats 
could be similarly beneficial for smalltooth sawfish, some 
shallow habitats in the Peace River, such as red-mangrove- 
lined tidal creeks, have increased habitat complexity and 
are spatially restricted, possibly limiting overall foraging 
success. Moving away from these shallow habitats into the 
slightly deeper main channel at night may improve forag¬ 
ing success in the Peace River, and the shallow mangrove 
creeks and shorelines may provide more of a protection 
function from bull sharks; these habitats are known to be 
used as refuging areas in multiple nurseries in Florida 
(Simpfendorfer et al., 2010; Poulakis et al., 2013, 2016). 
Shallow creek habitats in the Peace River may offer protec¬ 
tion from boat traffic and noise as well as from predators. 
A similar diel pattern in habitat use has been reported 
from passive acoustic monitoring conducted over many 
years in the Peace River (Huston et al., 2017; Scharer et al., 
2017; May et al., 2019), as well as from active and passive 
acoustic tracking conducted in other Florida nurseries 
(Simpfendorfer et al., 2010,2011; Poulakis et al., 2013,2016; 
Hollensead et al., 2016). All of these studies confirm that 
juvenile smalltooth sawfish refuge during the day in pro¬ 
tected creek habitats, especially those lined with red man¬ 
groves (Norton et al., 2012). Although the authors of some 
of these studies have proposed that smalltooth sawfish use 
deeper habitats to forage because of increased nighttime 
detections by receivers in main channels (e.g., Poulakis 
et al., 2016; Huston et al., 2017), the use of alternative 
shallow nighttime foraging grounds has been observed in 
other studies. For example, May et al. (2019) found that, 
although smalltooth sawfish in the Peace River crossed the 
deeper main stem of the river at night, they did so in large 
part to use shallow habitats that included oyster reefs on 
the shoreline opposite to their protected daytime refuge. 
Shallow mud flats and habitats within the main river chan¬ 
nel have also been reported as possible nighttime foraging 
areas for smalltooth sawfish in different Florida nurseries 
(Hollensead et al., 2016; Poulakis et al., 2016). Therefore, 
food availability and acquisition success may play roles in 
influencing where juveniles forage. For example, juveniles 
may forage in or near refuge locations when sufficient prey 
is available but venture farther into or across the main 
stem of the river if there is not sufficient prey or if densities 
of conspecifics near refuge locations are too high. 
In our study, burst events were recorded at depths rang¬ 
ing from 0.1 to 3.6 m, indicating that a variety of habitats 
are important foraging areas for this species. However, 
regardless of foraging location, the timing of heightened 
activity and foraging appears to be maintained across 
nursery habitats and populations, given that all previous 
studies have found heightened activity at night in the 
Peace River and other nurseries (Poulakis et al., 2013, 
2016; Hollensead et al., 2016; Huston et al., 2017; Scharer 
et al., 2017; May et al., 2019). 
Conservation implications and future directions 
This new information that relates putative foraging activ¬ 
ity to habitat use has improved our understanding of the 
early life history of the smalltooth sawfish and validated 
previous hypotheses about activity patterns developed 
through acoustic monitoring studies. Increasing ADL 
deployment times and deploying ADLs throughout the 
year in future studies would help to identify long-term 
foraging and activity patterns, particularly in associa¬ 
tion with seasonal changes in abiotic variables, such as 
temperature and salinity. Additionally, deploying ADLs 
concurrently with a tracking system that can detect move¬ 
ments on a scale as small as meters, such as a Vemco Posi¬ 
tioning System, would help to determine habitat use on a 
fine scale by enabling the matching of behaviors to specific 
sites within a nursery. Finally, conducting laboratory tri¬ 
als for validation of acceleration signals of smalltooth saw¬ 
fish or deploying video cameras concurrently with ADLs in 
the field would help to conclusively determine feeding and 
other behaviors. 
Even with its limitations, the information describing hab¬ 
itat use and potential foraging strategies provided by this 
study is valuable for understanding the habitat require¬ 
ments of this species and emphasizes the importance of 
preserving a variety of habitats, including mangrove-lined 
creeks used by smalltooth sawfish as refuging areas and 
less complex habitats used as foraging grounds within nurs¬ 
eries. This information will help to guide crucial manage¬ 
ment and conservation efforts for the smalltooth sawfish in 
the Peace River and throughout the range of this species. 
Acknowledgments 
This research was supported by funding from the National 
Marine Fisheries Service (grant NA13NMF4720047) under 
