Dive in to the Science Behind Discovery Channel's "Shark Week"

“Shark Week” may only come once a year, enrapturing summer television viewers with hours of footage of the ocean’s most powerful apex predators, but tagging, tracking and studying sharks is a full-time job for researchers at the Harte Research Institute (HRI) for Gulf of Mexico Studies’ Center for Sportfish Science and Conservation (CSSC).

This year, scientists with the CSSC set out with Discovery Channel’s “Shark Week” crew on a 10-day expedition to tag and study the Shortfin Mako shark, one of the fastest shark species in the world, for a special called “Monster Mako.” The show, which airs at 9 p.m. Central Time, Sunday, July 5, will help open the 28th season of “Shark Week” with unprecedented footage of scientific discovery and behaviors of Makos in their natural habitat.

With their high profile and sharp teeth, sharks have long been the celebrities of the ocean. TV viewers will get a glimpse of the work scientists are doing to better understand sharks, but there’s a bigger story to the science behind “Shark Week.” Despite a lot of public interest, scientists still have a lot to learn about sharks’ day-to-day lives in the ocean. Many sharks are pelagic, highly-migratory species and, because of their top predator status, they are necessarily rare. They live long lives (the notorious Great White Shark is thought to live up to 70 years), mature slowly and reproduce less than many other marine creatures. All of this makes it difficult for scientists to closely study sharks.

“Sharks play an important role in our ecosystem keeping things in check. And we know that when we remove these apex predators it can cause things to go out of balance,” said Dr. Greg Stunz, CSSC Director and HRI Chair for Fisheries and Ocean Health. “We know that shark populations are decreasing worldwide due to overfishing and other threats. We are seeing bright spots of recovery in many areas, but we still have a long way to go.”

TAGGING SHARKS

In “Monster Mako,” TV viewers will get to see exciting footage of scientists tagging Makos with some of the latest scientific equipment and cameras. CSSC runs a number of tagging programs to monitor shark populations in the Gulf of Mexico, and has tagged thousands of sharks to help fill information gaps about their lives in the Gulf.

The simplest CSSC tagging program is also its largest. Working with fishermen, CSSC has tagged more than 2,500 sharks along the Texas coast over the past six years, said Megan Robillard, CSSC program manager. This citizen science project gets anglers actively involved in collecting important information about sharks in the Gulf of Mexico. Tagged sharks are identified, measured and released and the catch location is recorded. Each tag has a unique ID number allowing CSSC to track individuals that have been recaptured and reported. As sharks are recaptured and reported, scientists can determine patterns in capture locations and seasons to understand migration and habitat use by sharks. The tags are cheap, at about $1 apiece, and a volunteer force of conservation-minded fishermen means many more sharks can be tagged.

The center also outfits sharks with acoustic tags, surgically-implanted internal tags that regularly sends out sound signals. With the help of a network of “listening” receivers placed in coastal inlets, scientists can track the sharks’ movement patterns over multiple years.

These methods of tagging have limitations, requiring recapture or that fish swim into listening arrays to gather information, Stunz said, and the data they gain can be limited. With passive tagging, for example, scientists only know where a shark was captured and where it was released and acoustic tagging is limited to the extent of the network. A shark may have traveled hundreds of miles in the meantime. But a third, state-of-the-art system of tagging is allowing scientists to track sharks in real time. The center has partnered with the Texas State Aquarium and the nonprofit OCEARCH to attach satellite tags to Hammerhead, Mako and Tiger Sharks, with plans to tag more in the future. The tag, which is attached to the shark’s fin, pings with a location each time the shark surfaces. This provides swift and accurate information about the shark’s current location, which is uploaded to a digital map so millions of shark fans can follow the shark’s movements online. This fall, an interactive exhibit will open at the Texas State Aquarium featuring this work.

“Satellite tagging gives us a much sharper picture of where these animals are going and insights into their behavior,” said Dr. Matt Ajemian, HRI Assistant Research Scientist. “One of the major data gaps out there is understanding where our Texas sharks migrate to and from. We know they’re highly mobile, so understanding their habitat needs and discovering if there are places they’re coming back to will be very important for their future management.”

Scientists took their work a step further for “Shark Week,” and employed a brand-new technology known as the “Shark Eye.” Scientists tagged Makos with state-of-the-art scientific instrumentation, including front and rear cameras equipped with night vision, and equipment to track the shark’s movement, depth, speed and acceleration. The instrumentation was designed to release from the shark after a day so scientists could retrieve the data. The goal was to capture the behavior of the Mako, a shark that tends to stay out at sea, and to measure its speed and acceleration.

“Prior to this, nobody had really attached cameras or instrumentation to a Mako shark to see what these animals do on a day-to-day basis. We wanted to capture social behavior and feeding behavior. Also, Makos are known for breaching, routinely jumping 30-40 feet out of the water to eat,” Stunz said. “Because of their speed and power, they’re a charismatic animal and a good ambassador for the ocean. We can use this interest in sharks like the Mako to convey a message about the importance of stewardship and conserving our ocean.”

ARTIFICIAL REEFS

During the “Monster Mako” expedition, researchers tagged nine Mako sharks ranging in size from 7 feet to 10 feet long at artificial reef sites off the Texas coast.

It wasn’t just a coincidence that CSSC scientists targeted artificial reefs to find Makos. After years of observation, scientists and fishermen alike know that these artificial reef structures, made of current and decommissioned oil and gas platforms, sunken ships and other manmade materials, attract an array of marine life — including the preferred prey species of the Mako Shark.

“It’s interesting because you have an animal that has the capability of traversing the entire Gulf of Mexico, but already from our own work we’re seeing that they can return, time and time again, to these artificial reefs,” Ajemian said.

Traditionally, the Gulf of Mexico is characterized by a sandy, muddy-bottomed environment without a lot of reef habitat. But oil and gas exploration in the Gulf of Mexico has changed that. Housing more than 3,000 oil and gas platforms, the northwestern Gulf of Mexico has developed one of the largest artificial reef systems in the world. These manmade reefs attract diverse communities of marine life, from coral colonies to the mighty Mako, and CSSC research has shown that they may add real productivity to the Gulf.

Since the 1990s, Texas Parks and Wildlife Department (TPWD) has operated an Artificial Reef Program, converting decommissioned oil platforms, ships and other material into a flourishing network of artificial reefs that enhance recreational and commercial activities such as fishing and diving. For the last three years, CSSC scientists have partnered with TPWD to conduct the first-ever large-scale monitoring program of life on Texas’s artificial reefs through both dive and ROV (remotely operated vehicle) surveys.

“One of the questions we have had is about shark habitat. Where are they feeding? Where are they breeding and raising their pups?” Stunz said. “Repetitive use of these structures provides evidence that we see sharks using them as stepping stones as they migrate throughout the Gulf, a phenomenon that we call connectivity. It makes sense because we’ve recognized over time that these structures definitely attract fish.”

Because these reefs are manmade, it’s important to develop a set of scientifically-based best practices for creating them, something that CSSC researchers are doing right now. Are there ways to increase populations of targeted species? How many reefs do you need in an area? And how do you maximize the goals of your program when placing a reef in terms of depth, geographic location or even reef orientation?

There’s a lot to learn. But researchers have already had some exciting results. In May, CSSC scientists published a study identifying a potential “sweet spot” on artificial reefs 150-200 feet below the surface where prized Red Snapper and other marine life flourish.

WANT TO KNOW MORE?

Still can’t get enough “Shark Week” science? HRI will host an encore screening of “Monster Mako” and a Q&A session with our shark experts at 6 p.m. Monday, July 6, in the Harte Research Institute building, conference room 127. This session is open to the public. Join us and learn more about the science that goes on behind the scenes to study these enigmatic sharks.

You can also chat with our CSSC scientists during “Monster Mako” (9 p.m. Sunday, July 5) on Twitter and Facebook with #MonsterMako.