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Predicting Sawfish Habitat in a Changing Environment

January 22, 2025

NOAA Fisheries and partners published research that identifies key habitat features of juvenile endangered smalltooth sawfish and predicts where else they could be.

A small, flattened, elongated ray-like fish with a long tootled snout rests in the water on a muddy bottom A juvenile smalltooth sawfish. Credit: Olivier Born (Permit #22078)

It’s not easy to study rare species. They can be hard to find when they are few and far between. Such is the case for the endangered smalltooth sawfish. NOAA Fisheries and partners have been studying sawfish for more than 15 years, and are learning more about them each survey season. Now, we’re preparing for how to study potential shifts in their distribution in a changing climate.

We can only monitor the population in a few places. So, our team—along with scientists from Havenworth Coastal Conservation and Florida International University—developed a new spatial model to predict where else sawfish may live. This will help us identify potential habitats outside our survey area based on key environmental characteristics where they were sampled. 

The research, “Predictive modeling of juvenile smalltooth sawfish habitats: challenges and opportunities for conservation” was published in the journal Ecology and Evolution on January 21, 2025.

Identifying Key Elements of Sawfish Habitat 

To identify key habitat features influencing the occurrence of juvenile smalltooth sawfish, we assessed long-term sawfish abundance data in relation to environmental data from where they were found—including water and mangrove tree properties. Fortunately, our long-term survey efforts have produced a large and valuable dataset of sawfish abundance and habitat traits. When we encounter a sawfish, we measure nearby environmental attributes including:

Image
A woman standing in water holding a sawfish
Dr. Andrea Kroetz prepares to release a juvenile smalltooth sawfish in Everglades National Park after collecting valuable biological information that is used to inform recovery actions for the species. Handling endangered species, such as smalltooth sawfish, is a permit-authorized activity. Credit: NOAA Fisheries (ESA permit 22078).
  • Mangrove canopy overhang
  • Mangrove root density
  • Water temperature
  • Water salinity
  • Water depth
  • Bottom substrate

"Models can only perform as good as the data they're fed", said coauthor Simon Dedman of Florida International University. "We're excited to learn key habitat features for this species, and are optimistic that ongoing improvements in data sharing will make it easier to do these kinds of analyses, to make it easier to protect species faster."

Predicting Sawfish Distribution

We used the results of spatial modeling to predict where else juvenile sawfish might live outside of our long-term sampling area. The predictions were based on areas with specific habitat features most strongly correlated with sawfish presence and abundance from our surveys. 

By analyzing more than a decade of data, we found juvenile sawfish rely heavily on very shallow, warm, saline waters fringed with dense mangrove roots.

Using these features, the model successfully predicted consistent sawfish presence beyond areas we currently monitor. This includes additional areas within the Ten Thousand Islands National Wildlife Refuge and Everglades National Park. While we do have many sample sites within the park, the model identified new places we’ve either never sampled before or have very limited sampling efforts. 

“We already know that Everglades National Park and Ten Thousand Islands National Wildlife Refuge serve as crucial nursery habitat for juvenile smalltooth sawfish, but our sampling efforts have limitations,” said Andrea Kroetz, lead author of the study. “The model provides additional evidence that juvenile sawfish are very likely present in other areas within this Critical Habitat that we haven’t been able to sample yet, which will guide us in future sampling and monitoring efforts for the species.”

The model domain covered one of the two existing Critical Habitat units, that were designated in 2009 to promote juvenile recruitment to the adult population. It could not predict sawfish presence outside this area due to a lack of high-resolution coastal environmental data. 

Now that we know what environmental characteristics are most important for juvenile smalltooth sawfish habitat, we know what data are needed to identify other important places. With higher resolution environmental data, this model can be a powerful tool to predict habitat for smalltooth sawfish beyond our sampling universe. It can also predict if sawfish habitat exists outside designated Critical Habitat units.

Healthy Habitats Support Recovery

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A map of Southwest Florida with multiple colors indicated predicted smalltooth sawfish abundance
Predicted smalltooth sawfish abundance in terms of catch-per-unit effort, or CPUE (numbers per hour) in Southwest Florida. Predictions of more smalltooth sawfish presence are denoted by warmer colors of yellow to red and locations with low or zero predictions are denoted by cooler hues of blue The inset panel shows these predictions for Whitewater Bay (WWB), Ponce de Leon Bay (PDLB), Snake Bight (SB), Little Madeira Bay (LMB), and Trout Cove (TC). Credit: NOAA Fisheries/Havenworth Coastal Conservation/Google Maps/TerraMetrics

The primary threats to smalltooth sawfish are habitat loss and bycatch in fisheries. Young sawfish rely on shallow estuarine habitats fringed with vegetation, especially red mangroves, as nursery areas. Coastal development in the Southeast United States has changed or destroyed much of this habitat. Continued development of these areas—in particular, the Charlotte Harbor Estuary Unit—threatens viable nursery habitats and could limit sawfish population growth.

These findings provide information that can be used to inform conservation actions to support sawfish recovery. As climate change continues to impact marine ecosystems, understanding the specific environmental preferences of threatened and endangered species becomes increasingly vital. Protecting mangrove habitats, especially in regions vulnerable to pressures such as coastal development and pollution, is critical for sawfish recovery. These habitats should be prioritized for protection and restoration.

The publication was led by Dr. Andrea Kroetz of Havenworth Coastal Conservation and included researchers from NOAA Fisheries and Florida International University.

Last updated by Southeast Fisheries Science Center on February 07, 2025