CSULB Professor, Former Student Studying Sharks…in the Desert, Using Mandalay Bay's Reef Aquarium to Study Eating Behavior

The words “shark” and “Las Vegas” are often equated with clever card players. However, the Mandalay Bay Resort’s Shark Reef aquarium is one of the finest marine exhibitions in the nation and offers an excellent venue for a professor and graduate from California State University, Long Beach to continue a study of sharks’ eating behavior this week.

Yannis Papastamatiou completed his M.S. in biological sciences in May as a student of CSULB Marine Biology Professor Christopher G. Lowe, an internationally recognized shark expert. Papastamatiou began his Ph.D. in zoology at the University of Hawaii at Manoa this August, but he returned this week to travel with Lowe to complete work he started while at Long Beach.
“I’ve always been interested in when, how much and how frequently sharks feed, especially because I used to work for the International Shark Attack File,” explained Papastamatiou. “We’d often hear recommendations of not to swim during the hours of darkness because that’s when sharks feed. When I started looking into this, there is actually very little scientific evidence to support those theories, and in fact, we know very little about when these animals feed, how often they feed or how much they feed.”

He thought that if he could determine when and how much stomach acid is secreted through studying stomach pH, a measurement of acidity, this would help establish when and how much animals ate.

Several years ago, Papastamatiou began his work with captive leopard and nurse sharks at the Long Beach Aquarium of the Pacific to see if his idea was feasible and to compare data between the two species.

“I got a device which measures pH continuously and stores that information on a data logger,” he explained. Hidden in a piece of fish, “the device is about 11 centimeters (4.3 inches) long, so it goes in the shark’s stomach and just sits there.” He later recovered the probes and downloaded the data to a computer.

The 1.6-million-gallon Shark Reef at Mandalay Bay is home to more than 2,000 species and is
accredited by the American Zoo and Aquarium Association. As part of its research and education program under curator Jack Jewell, Lowe and Papastamatiou will feed probes this Thursday to several nurse sharks, “and they’ll stay there as long as the shark want to keep it,” Lowe said. The sharks will probably keep down the probes for around 10 days, at which time either Lowe will return to Las Vegas or Shark Reef staff will collect them and return them to Cal State Long Beach.

Lowe and Papastamatiou will then compare the results between nurse sharks and leopard sharks. “The real question that we want answers to is how often do sharks eat,” Lowe said. “The problem is, for many species, that’s a really hard question to answer without having to kill a lot of sharks.” The probe method enables them to study sharks without harming them.
“This particular trip will hopefully finish off the last bit of data that we need to demonstrate that there are major differences in the gastric physiology of these two different species of sharks,” Lowe continued “What makes this so unique is that most vertebrates show a gastric physiology similar to that of mammals where they maintain low gastric pHs even when their stomachs are empty. The thought is that for organisms that feed on a regular basis, maintaining a low gastric pH may first involve energy saving in that you’re always ready for the next meal. The other advantage is that if you don’t have any food in your stomach, by keeping the pH low, you don’t develop a lot of bacteria.”

Lowe explained Papastamatiou’s earlier research revealed the theory “that nurse sharks may infrequently (maybe only once a week), and may have gastric physiology analogous to some snakes like pythons that also feed infrequently. They may be turning off their gastric pH machinery as a way to save energy. If we find that’s true, then this is the first time this has ever been documented in a fish.”

The study “dramatically increases our understanding of the vertebrate digestive system, sharks being one of the more ancestral vertebrates,” Lowe said. “The fact that they may show species specific differences in their gastric physiology, which has only been seen in reptiles, again gives us some insight into the evolution of this whole gastric system. Sharks were the one of the first vertebrates to evolve stomachs.”

Media Contacts:

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Anne Ambrose, external communications editor, 562/985-2582, aambrose@csulb.edu

Mandalay Bay Shark Reef – Jennifer Ramieh, Marketing Manager, 702/632-4574, jramieh@mrgmail.com