New Method May Improve Stingray Handling in Research

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New Method May Improve Stingray Handling in Research

©Janet Krenn/VASG

Bob Fisher and Kristene Parsons roll a cownose ray over onto its back, putting it into a deep sleep. ©Janet Krenn/VASG

By Janet Krenn, Staff Writer

Bob Fisher jumps into a tank with cownose rays—and they remain calm. They don’t zip away like other fish would. Instead, the stingrays with blunt noses seem curious. They swim over his feet and flap their wing-like fins on his leg. To an onlooker, these wild animals don’t seem stressed at all, and Fisher has found a technique to keep them that way.

As Virginia Institute of Marine Science (VIMS) extension staff affiliated with Virginia Sea Grant, Fisher has been studying cownose rays for years. In his efforts to understand the species’ migration habits, Fisher has tagged and released dozens of rays, a process that sometimes requires anesthesia.

“You never know exactly how an anesthesia will affect an animal,” says Fisher. What he does know is that he has to hold rays treated with anesthesia for days before they can be released, because the anesthesia stays in their systems and makes them groggy for some time. Those days in the tank can stress the animals and affect their survival when released.

That’s why he wants a more natural way to temporarily put the rays to sleep.

In the tank, Fisher and VIMS student Kristene Parsons demonstrate the low-stress method on a relaxed cownose ray lingering on the tank bottom. They reach down and quickly flip the ray over so its white belly is facing up. The ray starts flapping its wings, splashing enough water that the researchers turn their heads and squint their eyes.

“At first, they don’t like to be in that position,” says Fisher. But flipping the ray could be the key to avoiding anesthesia. For fish related to rays, rolling them over puts them into a deep sleep, called tonic immobilization, or TI.

In no time, the ray stops fighting. VIMS student Cassidy Peterson monitors its gill movements, occasionally updating Fisher and Parsons on the ray’s breaths per minute. Soon, its breathing is slow, steady, and relaxed. Then they flip the ray right side up.

It’s like snapping out of hypnosis.

“You get the swimming action right away,” says Fisher.

The first time the researchers attempted to put a cownose ray in the TI state, the team was nearly giddy when the ray recovered almost immediately. They tried the technique on each of the rays in the tank, and the result was always the same: deep sleep and then immediate wakefulness. Fisher tried the method repeatedly over the summer to determine its effectiveness, timing how long it takes before a cownose ray stops flapping its wings and monitoring its breaths per minute.

He’s optimistic that TI could change how researchers handle rays. Instead of bringing the animals onto land and keeping them in tanks, researchers could potentially put rays to sleep for a brief period without subjecting them to the stress of handling, transportation, anesthesia, and time in a tank. The benefits could extend beyond cownose rays to other ray species, for which anesthesia is currently the only approved method for sedation.

“If we can demonstrate it with this species, future researchers can utilize it and it could be better for the ray,” says Fisher. He is currently working with Parsons to publish this data so that the method can be validated and available for others.