Ten whale sharks gathered Friday, June 18, about 23 miles offshore and southwest of Sarasota, giving Mote Marine Laboratory scientists a rare chance to satellite-tag three whale sharks in our own blue backyard.
"People who have lived here 30 years have never seen anything like this. Usually whale sharks come to our waters transiently in ones and twos. This time we had 10 and we stayed with them for four hours," said Dr. Robert Hueter, Director of Mote's Center for Shark Research, who led a team to tag the sharks.
But this thrilling sight, an unusually large grouping for local waters, brings concern that large fish such as whale sharks might be changing their ranging patterns because of the Deepwater Horizon oil spill.
"We don't know that the spill is pushing large animals into our waters, but this unusual grouping of whale sharks suggests that we should consider that hypothesis."
The sharks showed no distress or unusual behavior. They were feeding on large clusters of what appeared to be fish eggs and other plankton. Whale sharks are plankton-eaters that strain food from the surface using a fine mesh of tissue in their throats.
Of the 10 whale sharks, Hueter and his team tagged two males and one female, each more than 20 feet long.
One of the sharks was a 23-foot female named "Sara" that Mote scientists had previously satellite-tagged on May 28. Now the researchers - and you - can follow Sara in real time from the link at the bottom of Mote's earlier release on Sara: www.mote.org/sara.
During her second tagging Friday, Sara was fitted with another kind of tag that will store location data for 180 days before it "pops up," floats to the surface and sends the data to Mote scientists via satellite. This tag is designed to last longer than the real-time tag and it will store data on water temperatures and how deep Sara dives, building a richer picture of her habits and environment in the wild.
"Sara is wearing a lot of jewelry now," Hueter said. "Having two tags is an insurance policy to make sure we get long-term data from her."
Hueter added that Sara's tagging may provide highly valuable information: "She looked pudgy, so she might be pregnant. If she is, we hope she will lead us to her pupping grounds - the area where she gives birth."
Learning where whale sharks mate and give birth is crucial to protecting the important habitats that support the survival and reproduction of this rare, highly vulnerable species.
Not far from Sara on Friday was Sota, a 25-foot male also satellite-tagged by Mote scientists on May 28.
Mote scientists satellite-tagged two more whale sharks on Friday - a mature male 25 feet long named "Dylan" and an immature male 22 feet long named "Gilbert."
Dylan's tag, which trails behind the shark on a tether, will beam out location data each time it surfaces. Gilbert's tag will store data for 120 days before detaching and beaming its findings to scientists.
Mote scientists don't know where these sharks migrated from, so cannot say whether they were driven near Southwest Florida's coast by oil in the northern Gulf of Mexico.
Whale sharks' travels are poorly understood, but Mote research has been shedding light on their migrations with 35 satellite taggings since 2003.
Mote's satellite tracking studies - mostly conducted near a summer feeding spot where whale sharks gather near Isla Holbox, Mexico - have revealed that some do travel to the northern Gulf. Others have cruised to the western Gulf of Mexico, waters between Florida and Cuba, the outer reaches of the Caribbean and other locations, even ranging south of the equator.
"It's unusual for so many whale sharks to appear near Sarasota, but not necessarily bad for their survival," Hueter said. "It's not what we expect to see in their life cycle, but they were finding food and appeared to be healthy. We don't know if the oil spill brought us this large group and we don't know how the spill will affect whale sharks in the future. But these are adaptable creatures and highly migratory. If the spill seriously threatens their range elsewhere, this area may provide a refuge."
If you see a large shark or large fish species abnormally close to shore, or if you see a large shark or large fish that appears to be in distress or behaving abnormally, please contact Mote's Center for Shark Research at 941-388-1827.
If you see a whale shark, please do not touch the shark from either a boat or in the water, as this could interfere with their feeding. Please do not interfere with scientific tags.