CHATHAM — The 50-pound severed tuna head drifted in the water off the back of the research boat like a decaying chew toy, dripping blood and oil, begging for a great white shark to emerge from the ocean and give it a taste.
Standing on the back deck, Captain Bob Yates bangs a cleaver down on a small herring, splitting it in two. He collects a handful of fish bits with his hands and throws them into a stained plastic bucket.
The 66-year-old’s forearms carry tatoos from voyages long passed, the ink so old the few words are no longer legible. One arm has an anchor, the other, a whale.
Mike McCallister, a 28-year-old research biologist from the University of North Florida, takes the bucket from Yates and pounds the fish into a thick paste with a shovel. He throws the concoction off the boat, the mush dissolving into the water.
The ship bobs lightly in the calm water a mile off Monomoy Island.
It is just after 10 a.m. and the two men, one a seasoned fisherman, the other a young shark scientist from Florida, are building a chum trail, hoping to coax a great white shark from the deep.
Just another Friday morning at the office for the team of about 20 researchers, fishermen, and videographers on an expedition to tag and collect blood and tissue samples from great white sharks off Cape Cod, before releasing them back into the water.
It was the expedition’s 18th day, and the team had hooked its first great white, a 12-foot-7-inch, 1,400-pound immature female, just the day before.
Now, they are back to the waiting game.
Such is life on a research boat searching for the elusive, fierce shark.
“It is all about patience” said Greg Skomal, a shark expert with the state Division of Marine Fisheries, sitting on a couch on the boat’s wooden deck.
“I don’t look down the road and hope for 20 sharks. I look down the road and I say, one at a time.”
The population of great whites off Cape Cod has exploded in the past 10 years as seals, a favorite meal, have grown in number. But not much is known about the formidable predators.
That is where Chris Fischer, the founder of the innovative if not eccentric ocean research nonprofit OCEARCH, comes in.
Fischer and his crew of expert fishermen, once the subject of reality TV shows, corral sharks all over the globe.
On this expedition, they bring sharks on board using a custom 75,000-pound cradle and give researchers from a dozen different universities and laboratories an unprecedented 15 minutes of access to the creatures.
They apply advanced tags that track where the sharks travel, allowing them to gather data on their behavior and environment.
It is all part of an effort to piece together the puzzle of the great white sharks.
But first you have to catch one.
The same crew was out in these waters last year and caught two sharks. With two weeks to go in this year’s search, they want to increase their sample size.
Leaning against the railing on the upper deck of a 126-foot Alaskan crab boat turned research vessel, Fischer, the expedition’s leader, was clearly exhausted, after a fruitless morning of fishing. Fischer took a break to call into a summer camp in Park City, Utah, via Skype and offer the latest on the expedition.
In South Africa, it is common for divers to drop into cages and let sharks swim up to them. Not here.
“These sharks here are totally wild, totally untouched,” Fischer said. “They are picky, they are nervous, they are genetically wary, and that has forced us to evolve and grow.”
“And that is great,” he said with a shout.
Fischer and his crew relish a challenge. This is their 17th expedition, and joining them is an eclectic group of researchers from the University of Massachusetts Dartmouth, the Woods Hole Oceanographic Institution, and the Mote Marine Laboratory in Florida.
OCEARCH provides a rare opportunity to get close to a live great white shark, said Robert E. Hueter, an associate vice president at Mote Marine.
“I’ve been doing this for 4o years, and I never laid my hand on a living great white” until working with the research team, he said.
Fischer’s unofficial slogan for OCEARCH, which he shouts all over the boat, is “inclusion!”
Then, as if on cue, Fischer excused himself to go include some more people.
“The Kennedys are coming,” he said on his way to the wooden deck of the ship.
Edward M. Kennedy Jr. and some of his family and friends were quickly approaching on a military-style work boat to attend a daily science briefing.
Kennedy was a summer intern at Woods Hole while studying for his master’s in forestry and environmental studies at Yale University and has remained an environmental advocate.
“My father would take us sailing and fishing, and we really learned at a young age that we need to protect these natural resources,” he said in an interview after the briefing, sitting atop a cooler full of rotting tuna used to bait sharks. “There is so much we don’t know about the ocean.”
The group toured the ship for a few hours, talking to researchers while fishermen in a separate, smaller boat continued the search for great whites.
It was just another day with OCEARCH.
Maria Shriver, Kennedy’s cousin, paid a visit the week before, while the soap opera star Joshua Morrow came aboard when the crew came to Cape Cod last year.
Celebrities can bring interest to shark research — Shriver tweeted about the expedition to her 2.2 million followers — but they are not the only ones who visit.
Community members and high school students are invited to come aboard, too.
But on this day, there would be no shark.
Back on the pier in Chatham, Fischer looked at Skomal.
Soon, he pledged, there would be a shark.
“Damn straight,” Skomal replied.
Fischer was right. The crew caught their second shark of the trip Tuesday. They named the 14-foot-2-inch, 2,300 pound immature female Katherine.
She swam off the boat’s cradle strong, another piece of the puzzle firmly in place.