Snook survive the cold water as Florida fishing season picks up.Researchers have spent the past seven years examining the long-term effects of two unique cold spells that struck South Florida in 2010, including different species' abilities to recover in the Everglades. In the case of the common snook, known to be sensitive to temperature changes, the researchers found location was a key factor in the fish's ability to survive the cold when temperatures dipped into the 30s. 

 

"Our findings were very surprising. If we look at the average temperatures throughout the entire ecosystem during the cold spell, no snook should've survived," said Ross Boucek, a biologist with Bonefish & Tarpon Trust who conducted the study as a Ph.D. student in biological sciences at FIU. "But if you zoom in on temperatures in different habitats, you see certain features allowed a couple of habitats to stay warm enough for a few fish to make it out alive."

While further research is needed, these findings show freshwater flow could help push snook to warmer habitats in the short time they have before water turns lethal when a cold spell strikes. According to Boucek, water temperatures remain constant in deeper habitats. Yet, when freshwater flow is lacking, snook are often concentrated in locations far from these deep water habitats.

Climate change is expected to increase the frequency and intensity of extreme climate events. According to Jennifer Rehage, FIU ecologist and scientist with the Florida Coastal Everglades Long Term Ecological Research (FCE LTER) Program, if researchers understand what keeps water temperatures warmer, and how and why snook seek refuge in those habitats, managers can understand their vulnerability and manage accordingly. 

Snook exposure to cold anomalies and possible lethal effects is governed not only by fish behavior, but by cold water and hot water mixing due to winds, river flow, tides and water depth, according to Tom Torgersen, program director of the NSF's Water Sustainability and Climate Program, which supported the research. 

"The effect on snook of any single extreme event should be viewed in terms of the physical conditions in which it happened, as well as the biological processes that affect snook distribution."

FCE LTER Program monitoring networks provided the scientists with long-term data on environmental conditions. The scientists outfitted more than 100 snook with acoustic transmitters, following their movements throughout the Everglades. Housed at FIU, the FCE LTER Program is part of the National Science Foundation's (NSF's) LTER Network.

"Sudden changes in water temperature due to cold snaps may have lethal effects on many economically important species of fish and other marine creatures," said John Schade, program director in the NSF's LTER Network. "The risks to these species are especially high when they are unable to move to more hospitable environments. In a world where extreme climate events are becoming more common, studies like this are critical to our ability to manage fisheries we need to feed growing human populations."

The study was published in Global Change Biology. It was funded by the National Science Foundation with support from the Everglades Foundation.