Gina, measuring 8 feet 2 inches long and weighing 302 pounds, was tagged in the pass on June 14.
Mote research scientists returned to the Boca Grande Pass on Monday, July 8 to continue the shark-tagging program that is part of Mote Marine's larger shark initiative. Local fishermen hooked the animals and brought them alongside the Boca Barge where Dr. Bob Hueter, Dr. Jack Morris and a small group of interns and staff waited to measure, assess, tag and release the sharks in as little time as possible.
The study, funded by the Guy Harvey Ocean Foundation, will show the location of the animals over time and give scientists a better idea of where great hammerheads and bulls, the two species being studied, go during the part of the year they're not in our passes feeding on tarpon.
Two types of tags were fixed to most of the sharks: A non-electronic identification tag attached to the tip of the dorsal fin that provides instructions to fishermen if the shark is caught and a satellite tag attached at the base of the dorsal fin that collects and stores data.
View More images >>The satellite or “pop-up” tag stores data until a predetermined time, then detaches itself and floats to the surface and reports them.
Another type of tag, a “spot” tag, is available. Unlike the pop-up tags, it reports activity while still attached, Dr. Hueter said, but they have to be used judiciously due to their prohibitive cost. The satellite tags range in price from $1,500 to $4,200. He was hoping to save their last spot tag for a hammerhead, should they catch one.
The great hammerhead proved to be the more elusive of the two species by far, at least on Monday. Five sharks were tagged, all bulls. Two were immature males around 6.5-feet long that were given ID tags only, and the remainder were mature female bulls. The males were caught and tagged before press arrived on board.
The first call came over the radio shortly before 1:30 p.m. A large bull had been hooked. The capture was uneventful and Margaret was tagged for identification, affixed with a 90-day pop-up tag, measured, assessed and released just after 1:30 p.m. She measured 8.5 feet.
Sue and Sharon would prove more troublesome.
Both fought their anglers longer, and resisted efforts to attach a tail- rope, the last step before passing control to researchers on the barge. There was a very real tension, belied by friendly banter between the fishermen and researchers while they fought her. Capt. Robert Moore and anglers Lee Crosby and Bret Theriault hooked all three female bulls, and there was nervous laughter as Sharon missed Theriault's arm by only a few inches several times.
That tension gave way to a different kind after the animals were transferred to the barge.
“Target time for release is under ten minutes,” Dr. Hueter said. “Fifteen if we’re using spot tags.”
Hueter and colleagues use a standardized scale to assess the shark’s condition upon release, depending on how it swims away from the boat, among other things. Hueter could also be seen making related assessments during the measurement and tagging, tapping his fingers around the shark’s eyes, for example, to see if the nictitating membrane was functioning reflexively, an indication of good health.
It was also important to release them in the right place.
“Sharks do what we call ‘yo-yo’ diving when they’re released for up to a few hours, so we try to release them in deep water. It’s sort of like catching their breath,” said Hueter. Sharon had to be transported a few hundred meters to deeper water to be released, increasing the time spent alongside the barge. Neither a long time on the line, nor a quick release in shallow water were ideal; she was hooked 49 minutes before her release and had put up a protracted fight.
“After 30 minutes of fight time,” said Hueter, “it gets a bit dicey.”
But when she swam away she did it with a reassuring thrash of the tail. She was the biggest shark tagged Monday at almost 9 feet, and may have been in the early stages of pregnancy. She was outfitted with an ID tag and a six-month pop-up tag.
Hooks proved too difficult to retrieve from the three female bulls. Dr. Jack Morris said that, for example, when the hook is embedded in the jaw rather than passing through it removal is nearly impossible.
“That cartilage tends to bind around the hook,” he said.
Fortunately Moore, Crosby and Theriault, the same volunteers who caught all three female bulls, used nonstainless hooks that will corrode and dislodge themselves.
The information collected, along with knowledge about gestation times, location of pups and whether or not the sharks are pregnant at the time they’re tagged, will let researchers determine how far sharks range during the year, where they go to give birth and other valuable information such as whether the sharks follow tarpon offshore or stay in the pass. Morris said that though they’ve been collecting data on sharks here in the Charlotte Harbor area off and on for about 10 years, the focus has changed to reveal what they hope will be a better picture of the dynamics of the pass and surrounding waters and how sharks here interact with tarpon.
The data will be available, said Hueter, to inform sensible management among other things.
“Management has been difficult,” Hueter said. “About 95 percent of fishermen can't identify many species.”
That leads to difficulties like inaccurate data reported from anglers to accidental harvest of protected species.Bulls are not currently protected from harvest, though there are limits on size and number that can be taken, and great hammerheads are listed on the FWC’s site as protected under state regulations, though they’re not currently protected in federal waters.
That could change, said Hueter, as the National Fishery Service is considering a change in classification. Hueter said that he hopes data from the study will show whether sharks are staying in safe waters or not, especially the great hammerhead, about which less is known. In the Bahamas, no shark harvesting is permitted, but in Cuba, sharks are not protected at all, he said.
Though the Guy Harvey Ocean Foundation has provided funding through the end of the season, Hueter said, more fundraising efforts will be necessary for long-term study.
“We hope to be here for many more summers,” he said.
Hueter and his team will be in Pine Island Sound netting juvenile black tips to assess their abundance before possibly returning at the end of July for four or five more tagging-days like Monday’s, according to Morris. So far they’ve tagged about 12 large sharks.
They only have one more satellite tag and one spot tag they’re hoping to put on a great hammerhead, Hueter said.
Though none of the sharks was given spot tags Monday, those that were can be tracked via OCEARCH’s website, sharks-ocearch.verite.com/.
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