Study shows red tide may have hurt stone crab season
SARASOTA- Red Tide may be out of our Suncoast Waters, but stone crab season could take a hit for years to come.
“With the recent red tide lasting 18 months,” Dr. Gravinese said. “It overlapped with the stone crab reproductive season, and so we were thinking that maybe there’s a chance the red tide toxins might have an effect on the larvae.”
Mote Marine Lab Postdoctoral Research Associate Dr. Philip Gravinese says their research exposed stone crab larvae to different concentrations of red tide.
“Under high concentrations of red tide,” Dr. Gravinese said. “There was100% mortality within 48 hours.”
Larvae did better under medium concentrations with mortality rates between 30 and 40%. But that’s not a good sign for the local population.
“The August-September time line was elevated,” Dr.Gravinese said. “High concentrations over one million cells per liter, even far greater than that, I mean off our docks here at Mote, there were days we recorded, 90 million cells per liter.”
Dr. Gravinese says locally the stone crab catch is down about 60% in recent years, but that
“The larvae take about a year and a half, two years to get to adult size, so if you’re reducing the larval supply that’s in the wild,” Dr. Gravinese said. “Then it’s possible that down the road one or two years from now, we might have less.”
Continued studies are planning to look at the effect of red tide of juvenile populations as well as the effect of hypoxic or oxygen deprived water conditions that follow a red tide bloom.
“During those hypoxic conditions,” Dr. Gravinese said. “We have evidence that the crabs aren’t as tolerant to that hypoxia when it’s prolonged several days in a row.”
Mote Marine Lab says results in field tests could vary because red tide concentrations could change in deeper water.