OT - A Bunch Of Lemons ...

[ricki]

Sharks, to be more accurate and right here in Jupiter!


From: http://dixiediver.com/

A pretty good UW video appears HERE

"UM professor discovers mysterious gathering of lemon sharks off Jupiter Inlet

By Stephen Deere
South Florida Sun-Sentinel
Posted March 21 2006

For a man who had spent a lifetime researching sharks, what Samuel Gruber saw diving four years ago off the Jupiter Inlet was nothing short of a religious experience.

About 100 adult lemon sharks hovered over the ocean floor in about 90 feet of water.

Throughout his 40-plus-year career, Gruber had seen maybe 15 or 20 adult lemon sharks, distinguished by their yellowish brown tint and dual dorsal fins.

"In one day I saw more adults by a power of five than I have in my whole career," said Gruber, 67, who has visited the site between December and March every year since.

Nowhere else in the world does such a phenomenon exist, Gruber said. And Gruber, among the world's leading authorities on sharks, has been trying to answer a simple question: What brings them here?

Gruber's initial theory is that female sharks are emitting chemical signals called pheromones that attract male sharks. But why they've chosen this particular spot to conduct their courtship remains a mystery. Does it have something to do with a combination of the currents, water temperature, and its salinity?

This year, getting closer to those answers proved more difficult. Not nearly as many sharks showed up.

The number of sharks fluctuates from year to year, Gruber said, and he's confident that more sharks will return. "You have good years and you have bad years," he said.

Next winter, he hopes to start testing his theory. He plans on collecting water samples around some of the female sharks and testing the water chemistry or possibly extracting urine samples from the females.

Juvenile lemon sharks are relatively easy to study. They congregate in nurseries in bays or lagoons. They prefer the safety and plentiful food supplies at mangroves and in warm shallow waters, such as those at the Bimini Biological Field Station, about 50 miles east of Miami, which Gruber owns and runs.

But once the sharks reach about 3 years old, they vanish.

"We really don't know anything about the adult phase," said Tristan Guttridge, one of Gruber's principal investigators. Guttridge, 23, of Leeds, England, is planning on writing his doctoral dissertation on the shark gathering.

Because so many gather in such a small place, the sharks are particularly vulnerable. The aggregation of lemon sharks near the inlet could prove attractive to commercial and recreational fishermen as well as divers. Gruber and others worry this unique occurrence could be exploited.

"This is a natural phenomenon," Guttridge said. "It's something we should be taking care of, preserving rather than destroying."

In some years, the aggregation consists of as many as 50 female sharks that produce 600 to 700 babies per reproductive cycle. If the site gets heavily fished, it could decimate the lemon shark population all along Florida's coast.

"They are all jammed into this one spot," Gruber said. "It makes them vulnerable as hell."

Out at sea one recent morning, Gruber wore a baseball cap, jeans and orange Windbreaker. When the sun was out, a bandana covered his face and neck to protect against skin cancer. Swells rocked the 31-foot boat Friendship as Gruber sat in the back cutting up ballyhoo and tossing them into the water. He hoped to outfit at least one shark with a transmitter so he could track its whereabouts. But the sharks weren't biting.

To catch the sharks, freelance photographer Walt Stearns dives off the boat and spears a couple of barracuda, which are promptly cut up and used for bait or chum.

Stearns first alerted Gruber about the gathering after he witnessed it while diving one day in 2001. Later, he said he called Gruber at his home in Miami to tell him about what he witnessed. Gruber didn't believe it.

"He thought I was on drugs," Stearns said.

Then Stearns e-mailed him pictures.

Although Gruber, a professor at the University of Miami, has been coming to the site for four years, his research is just getting under way. Gruber has only received one $5,000 grant to study the sharks. This past winter he depended on individual generosity to conduct his research. After being approached by a mutual friend, Friendship Capt. Dominic D'Angelo agreed to take Gruber, along with two of his researchers and Stearns, out on the water for free for a couple of days.

Gruber said he will retire from the university next summer. And he is now in talks to transfer ownership of the Bimini Biological Field Station. After those two things take place, he hopes to focus all his efforts on the adult lemon sharks gathering near Jupiter.

"We haven't really started yet," he said.

Stephen Deere can be reached at scdeere@sun-sentinel.com or 561-228-5506."

From: http://www.sun-sentinel.com/news/loc...home-headlines