Listening to Fish in Florida Bay: Understanding impacts of Freshwater Runoff on Estuarine Fish Behavior

Aaron Rice, Ph.D. January 9, 2018

As freshwater drains south through Florida from Lake Okeechobee into the Gulf of Mexico, it travels through the Everglades and Florida Bay at the southern tip of Florida. This freshwater is critical for providing South Florida with water for drinking and agriculture, but flow is closely managed and regulated to account for major seasonal differences in water availability between the wet and dry seasons. One of the key questions in this freshwater management effort is how it impacts the saltwater fish living in Florida Bay.

View of Florida Bay, showing the calm seas. Average depth of the entire bay is approximately 3 feet
Florida Bay and the study area

In a collaboration between Cornell and the National Park Service, we have been using acoustic recorders to document fish sounds across the bay, and how the amount of these fish sounds varies throughout the year, across the bay, and under different water conditions. We attached our recorders to an existing network of water monitoring stations across Florida Bay and Everglades National Park, so we can collect audio data in tandem with environmental data.

NPS water monitoring station and acoustic recorder at Buoy Key, in Western Florida Bay. Buoy Key was one of the sites of the massive seagrass die-off in 2016
National Park Service water monitoring station near the entrance to Joe Bay, part of the Crocodile Sanctuary within Florida Bay

Approximately 200 species of fish are found in Florida Bay, and nearly half of those species have been documented to produce sounds. Acoustic communication plays an integral role in the life history of many marine vertebrates, especially marine mammals and fishes. Unlike other communication modalities, acoustic communication can be observed remotely and passively and used to assess species-specific patterns of occurrence and behavior. These surveys result in a permanent historical record that can be used to investigate a wide variety of species and habitat conditions. Thus, passive acoustic recordings provide a promising survey methodology to quantitatively evaluate community responses to environmental change in the context of conservation and restoration efforts.

Vocalizations of Gulf toadfish recorded in Apalachicola Bay, Florida. Sound courtesy of Luke Remage-Healey and Andrew Bass

The observed ecological responses will directly inform adaptive management strategies of the park. This project will also demonstrate how passive acoustic fish surveys can be used as an effective approach to increase understanding of broader management, conservation, and restoration efforts across Florida Bay and Everglades National Park. This collaborative effort between the National Park Service and Cornell University could result in several valuable and exciting scientific and management outcomes. The large-scale acoustic monitoring of fish populations in the Everglades would provide detailed data on the diversity of fishes within the park and reveal how fish populations and communities are affected by changing environmental conditions or human activities. As the project continues, we will gather continuous data on multiple fish species in the park and evaluate the frequency of their occurrence and reproductive activity. Going forward, it could be possible to have several permanent recording platforms across the park with continuous documentation of the status of different fish sounds or populations at different locations through time.