New research from Mote reveals stone crabs could feel effects of red tide


SARASOTA – Dr. Philip Gravinese does post-doctoral research at Mote Marine Lab.

He says the stone crab fishery has some good years, and some not so good.

“This year was a particularly bad year,” Gravinese said. “Last year was a little bit better, so we think there are some cyclical changes that happen.”

Gravinese says it’s hard to tell what causes a bad season.

“It could be larval supply; it could be results from the hurricanes; it could be environmental changes,” Gravinese said.

Like fluctuations of red tide.

The toxic algae is known to cause respiratory issues for us and release a neurotoxin that kills fish.

Gravinese is trying to figure out exactly what it does to the stone crabs.

“The study that we did in the lab, we controlled the red tide conditions to mimic a severe outbreak,” Gravinese said.

The experiment was on sublegal crabs, meaning they’re still too small to enter the fishery.

“[The study] showed that over long periods of time, so we exposed them for 9 days, they had a significant decrease in their stress response, but also their survivorship,” Gravinese said.

So the red tide effects on the crabs could have implications for the next crab fishing season, but Gravinese says the study left his team with more questions than answers.

“If they accumulate any toxin in the tissue, so that’s one for sure,” Gravinese said. “ it affects the adults, so the legal sized crabs, which we didn’t look at.”

And whether there’s any impact on the juvenile crabs and the larvae, which during the summertime get transported offshore, where Gravinese says the red tide bloom develops.

“So if they are not tolerant of the neurotoxin or the red tide itself, that could be trouble as well,” Gravinese said.

These questions he hopes to answer with even more research.


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