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Florida scientists are mapping red tide fish kills to help regulate fishing afterward

a dead fish on a beach
Jessica Meszaros
Dead fish washed ashore after a red tide event in 2018.

Satellite images of red tide blooms in the Gulf of Mexico and modeling from within the water column will then be combined with a foodweb model to estimate mortality rates of different fish species.

Florida researchers are working to map fish kills after red tide events to help regulators determine harvesting limitations. The National Oceanic and Atmospheric Administration awarded the five-year project with about $1.7 million.

Toxic red tide algae blooms can result in large fish kills.

David Chagaris, a research associate professor at the University of Florida's Nature Coast Biological Station, said the Gulf of Mexico Fisheries Management Council often doesn't have enough information about the events to create safe catch levels in the following years for species like grouper and snapper.

“If there's a red tide that's occurring, they oftentimes don't have enough information to say, ‘Well, the effects are going to be severe or not so severe,' " Chagaris said. "And so, they don't have that information to then say what would be the safe catch levels in the following years.

“So, this project … it aims to create this modeling framework that can provide that information on a timely manner for managers when setting catch limits.”

There are three components to the project:

One involves satellites. Chuanmin Hu, with the University of South Florida College of Marine Science, will use a new satellite to detect red tides from space to have near real-time information.

Part two involves biogeochemical modeling with Mike Stukel at Florida State University.

“That will allow us to understand more about the role of red tide across, up, and down, throughout the water column, instead of just a surface because the satellite only detects surface blooms,” Chagaris said.

He said both of these will feed into the third component: Chagaris’ ecosystem model.

“Like a foodweb model that has about 80 different species in it, and they're connected to one another through foodweb interactions and fisheries,” he said.

“We can take … the information from the satellites and the biogeochemical model overlaid on our ecosystem model. And from that, we can then estimate what would be the mortality rates on those species due to red tide. And that then feeds directly into the stock assessment in the management process to help managers make better informed decisions.”

But he said this will not always result in less catch for fishermen because in the past, without this information, he said the Management Council and its scientific advisory bodies have been overly precautious in setting the catch levels.

“This will allow them to kind of thread that needle a little bit better to … promote the sustainability of a stock, but not also take too much catch away from fishermen when the red tide is not so severe," Chagaris said.

He added that they hope to predict what fishing regulations will look like in 20-to- 30 years combining the red tide data with climate change figures. 

“When we link the ecosystem model with the biogeochemical model, that opens the door for us to then bring in some climate forecasts because the biogeochemical model is more accommodating to like the ocean climate projection forecast,” Chagaris said.

“And so those could drive the biogeochemical model, which could then make predictions about red tides in the future, or … whether they're likely to be more frequent or severe.”

My main role for WUSF is to report on climate change and the environment, while taking part in NPR’s High-Impact Climate Change Team. I’m also a participant of the Florida Climate Change Reporting Network.