Ocearch finds sharks - and much more - in Gulf of Mexico

This story originally aired on November 13, 2015.

Ocearch is wrapping up its first-ever expedition in the Gulf of Mexico. The Gulf has received enormous attention in recent years, mostly for what went wrong -- the Deepwater Horizon oil spill, to start. But five years after that disaster, parts of the Gulf are teeming with life, providing Ocearch a rare chance to study how many sharks are there and where they're going, reports CBS News correspondent Jeff Glor.

Meet Finley. She's a 10-foot long tiger shark, the first Gulf shark to be spot-tagged on Ocearch's crab boat-turned-laboratory.

The group of scientists and fishermen just wrapped an expedition off the coast of Texas.

"Tiger sharks love to come into beaches and estuaries as well as roam offshore," expedition leader Chris Fischer said.

During the Gulf expedition, Ocearch tagged four sharks, two tigers and two hammerheads, with GPS trackers. They are posting all the data to their popular tracking website, in the process bringing global attention to a body of water with an often muddy reputation.

"A lot of people think of the Gulf as a mess -- largely because of the spill. What kind of shape is the Gulf in?" Glor asked Fischer.

"I think the Gulf's in pretty good shape. I mean, if you talk to the people who are out there fishing, it's rebounding, full of life," Fischer responded.

And, he hopes, full of sharks. Remove too many from their natural place at the top of the food chain and second-tier predators would roam, uneaten and unchecked, devouring smaller fish populations and throwing the entire eco-system off-balance.

In the Gulf, Ocearch is cautiously optimistic. Finning, one of the biggest threats to shark populations, is not as prevalent here. Over the past few decades, the influx of oil rigs also has created just as many artificial reefs.

About 30 miles offshore, there are about 4,000 active oil rigs in the Gulf. Above water, they are steel, stark and industrial. But underwater, there's an explosion of life.

"These oil and gas platforms have been in for decades. No one quite realized how great ecosystems would be formed around them," said Greg Stunz, director of Sportfish Science and Conservation at Texas A&M University-Corpus Christi. Stunz is one of the scientists working with Ocearch in the Gulf who has gone diving in the reefs.

"One -- it's just the sheer size is quite amazing. Of course, from the surface of the water it's flat, it looks like nothing, but as soon as you dive down just a few feet and you see a size of a building of, you know, this size underwater," Stunz said. "And then, of course, the next thing you see ... is just the abundance of marine life, particularly fish that are just everywhere."

Over time, man-made structures like oil rigs become artificial reefs by attracting an entire food chain -- microscopic organisms, coral, schools of fish and, eventually, the lions of the oceans: sharks.

The structures also attract controversy, usually when a rig is retired and a decision needs to be made: Should parts of it stay -- and be permanently reefed -- or go?

"Many say it's ocean dumping, you're just leaving the trash. But believe it or not, the oil and gas companies don't necessarily want to do this," Stunz said. "The scrap value of the steel is worth way more for them to bring it in. ... A lot of the concern that some in the general public or environmental community might have is that it's oil and gas, and oil and gas doesn't always have the best reputation."

"Look, ocean first. Great-grandchildren first," Fischer said. "If you want an abundant future for the Gulf of Mexico, it would be an absolute catastrophe to not reef every single one of those rigs you can."

For now, Big Oil's trash is Fischer's treasure. Finley and her friends will provide data scientists have never had -- where Gulf sharks are mating, breeding and traveling; what role artificial reefs play; and what threats are real, versus imagined.

"It's kind of crazy to be pioneering this kind of work in 2015. You know, you would have thought it was done a long, long time ago. ... And it's crucial, because we should all be absolutely terrified of an ocean with no sharks. If that is the case, there simply will not be fish sandwiches for our children to eat," Fischer said.