Stone crab larvae perish from red tide, but bloom intensity matters

Mote scientists and Pitzer College partners aimed to better understand how newly hatched larvae might be affected by a bloom of Florida red tide (Karenia brevis) persisting into the stone crabs’ summer reproductive season. K. brevis blooms typically occur in the Gulf of Mexico from early fall into spring but can last a year or more — as did the severe bloom from late 2017 into early 2019.

This study is the latest of several Mote projects investigating multiple stressors to stone crabs, with the goal of better understanding the 25% decrease in southwest Florida’s yearly stone crab catch since 2000 and informing resource managers working to help the fishery rebound. The study was supported by grants to Mote from The Steinwachs Family Foundation and The National Science Foundation Research Experiences for Undergraduate program.

“Our previous research suggests that sublegal stone crabs, whose claws are nearing legal harvest size, have a short window of tolerance for elevated concentrations of Florida red tide algae and begin to die off when that window is exceeded,” said Mote Postdoctoral Research Fellow Dr. Phil Gravinese. “This is one possible way that red tide might reduce the catch rate. Alternatively, severe and prolonged blooms that overlap with the crabs’ summer reproductive season might be reducing the number of offspring, or larvae, that are available to recruit into the fishery.”