Looking out for leopard sharks, Birch Aquarium completes their annual check-up

A leopard shark swims at Birch Aquarium in La Jolla.

July 31, 2022 4 PM PT

Though the popularity of “Shark Week” on the Discovery Channel draws attention to sharks from around the world, a team of veterinarians at Birch Aquarium in La Jolla has been examining the sharks found right in our backyard.

In late July, Birch’s leopard sharks got an annual check-up during which aquarists measured their total weight, length and girth; examined their eyes, gills, fins and skin; and drew blood and collected data on each one.

“The value of understanding the sharks’ physical condition as well as chemical makeup is really important for their life cycle as a whole,” said Jenn Moffatt, senior director of animal care, science and conservation at Birch Aquarium, part of UC San Diego’s Scripps Institution of Oceanography. “We track their weight over time just to make sure our animals are stable and have good body conditions.”

A team measures a leopard shark in Birch Aquarium's care as part of an annual check-up.

According to Birch, most sharks, including leopard sharks, have five gill slits on each side of their body, which the team checks to make sure they are working properly.

The experts also check the caudal (tail) fin, which sharks use to generate power and swim forward; the pectoral fins, on the sides of the body, which are used to steer; and the dorsal fin, on top of the body, which is used for stabilization.

They also look for abnormalities in the skin.

Each check-up takes only 10 to 15 minutes, but an immense amount of coordination goes into the planning.

“It’s interesting for us to have all the team players — the divers, veterinarians, curators, members of our husbandry team — all working together to achieve a goal as quickly and safely as possible,” Moffatt said.

First, they have to catch the sharks.

“We use divers, nets and barriers to move them from their habitat to a secondary pool, where we put them in a state of tonic immobility, which is basically when a shark is rolled upside down and goes to sleep. It’s a natural function for a majority of sharks to do that, so we can limit restraint and have it be a natural process,” Moffatt said. “When we’re done, we roll them over and they are instantly back awake. Within 30 minutes they are eating again.”

But catching and calming them isn’t the hardest part.

The biggest challenge, Moffatt said, is drawing blood, given the different sizes of the sharks and the density of their tails.

“Sometimes the ‘meat’ of the tail of one shark is different from the meat of another shark tail, so getting the needle in to actually draw the blood can be a challenge. Once you hit the blood, you’re set, and when we get the blood work back, we see they are doing great.”

With the blood work, the team can track the sharks’ nutrition and figure out whether any adjustments need to be made to their diet.

Birch aquarist Maddy Tracewell said leopard sharks are one of the most common sharks off the coast of California — especially in La Jolla Shores during the summer, when pregnant females go to shallow waters — so having them in a nearby aquarium provides valuable opportunities for people to learn more about them. Then they can go into the water and see them up close, which “fosters a connection between people and sharks,” she said.

“A lot of people are scared of sharks, but leopard sharks are not one to fear,” Tracewell said. “They are very docile and safe. I think they are really cool animals, but they are misunderstood, so I enjoy getting up close and personal with them. It is fun to interact with them.”

Snorkelers swim with leopard sharks in the clear, shallow water of La Jolla Shores in 2019.

Leopard sharks get their name from their spotted skin and average about 5 feet long, Tracewell said.

“They are what is known as benthic animals, meaning they dig for their food at the bottom of the ocean,” she said. They give birth to live pups.

“We can use them to see what is happening in the ocean,” she added. “Their migration and breeding habits could suggest changes to the availability of prey items.”

La Jolla Shores is considered a Marine Protected Area, and seeing large groups of pregnant females in the shallow waters “shows what a successful MPA looks like,” Tracewell said.

Moffatt said she appreciates that sharks are prehistoric and are “so efficient and resourceful as predators. And they are strikingly beautiful.” ◆