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By Jim Westhoff

Every week is shark week for David McElroy.

Tucked away in a corner of Lewes, near the Coast Guard station, the young scientist has been conducting research on brown sharks, or Carcharhinus plumbeus.

The doctoral student from the University of Maine spent all summer catching small brown sharks and observing their diet and digestion rates. He use large tanks to strictly control their diet and monitor how fast they digest the food.

He came to Delaware because he said Delaware Bay is a hot spot for brown sharks. “Delaware Bay is a major nursery for them,” he said.

“The theory for that is the large number of estuaries provide protection for the young from predators.” He said there are probably thousands of brown sharks in the Delaware Bay.

But before you leap for the spear gun, he said they hardly ever attack humans. “Their favorite food is menhaden,” he said.

McElroy said he spent all summer walking in the tank among the sharks, handling them, and he has nary a scratch.

He studies their digestion rate by first tagging each shark, then feeding each one a specific amount of fish. A few days later he will then check the contents of each shark’s stomach.

There are probably more dramatic methods of checking what is in a shark’s stomach, but McElroy catches each shark with a net, then, inserts a PVC pipe past the mouth of the animal into its stomach.

He uses a technique called “everting” to turn the shark’s stomach inside out, so it is at the shark’s mouth.

The contents will then fall onto a screen. McElroy then weighs and examines the contents – and while the process sounds unusual, he says it does not injure the shark.

“They probably don’t like it, but it doesn’t cause any damage. Some of them eat a few hours after I evert them.”

Their durability is one reason McElroy likes brown sharks so much.

“They are beautiful, amazing creatures,” he said. “They are incredibly adaptive to the environment. They were here before dinosaurs. Their senses are highly developed and they are very successful predators.”

McElroy is working cooperatively with Apex Predators Program of the National Oceanographic and Atmospheric Administration fisheries division, University of Rhode Island, University of Delaware and the National Aquarium in Baltimore.

To catch the sharks, he uses a 1,000-foot line with 50 hooks and heavy wire leaders.

He said the heavy leaders scare away most other species of fish. “I guess the brown sharks don’t care,” he said.

He studies sharks that are relatively young, about 2 1/2 feet long. He said brown sharks mature in about 15 years and can grow to 8 feet in length.

With a story to tell, the sharks were released Sept. 6, and McElroy headed back to Rhode Island, where he’s a student, to write his dissertation and start student teaching.

His parents are probably glad he will leave the shark tanks for now.

“My mom would prefer that I studied starfish or something, but they’re just glad I enjoy what I do,” McElroy said.

Source - Cape Gazette