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Senior aquarist Colleen Hill shared this story of about the newly hatched skates. We thought you'd enjoy it too.
Occasionally at Hatfield Visitor Center beachcombers find “strange plastic-looking brown items” on the beach. These are skate egg cases that have washed up on the shore. Visitors often bring them into us and want to learn more about these strange things they have found. We enjoy the opportunity to teach the visitors about the skate egg cases.
Big skate egg cases are large (~12” X 4” X 2”), rectangular, dark brown, and made of thick collagen proteins that have an appearance and feel like thick plastic. Each egg case of the big skate can contain 2 to 7 eggs. Usually, when these egg cases arrive at the Hatfield Visitor Center, they have been rolled around in the surf so much that the eggs inside are liquid due to being shaken up and therefore they are not viable. In other cases, the egg cases come to us completely dry due to being in the sun on the sand. Again these egg cases are not viable. It is rare for a viable big skate egg case to be found and come to us in good condition, but it can happen!
On January 14, 2019, we were fortunate to have a donation to the Hatfield Visitor Center of a viable big skate egg case that was found locally, but it was not without a little drama at first. One of our very own Hatfield Visitor Center Interpretive Volunteers and an avid beachcomber stumbled upon a big skate egg case during a walk along the ocean in South Beach.
When she arrived at the Visitor Center with the egg case in hand I gave her my normal public service announcement that it probably isn’t viable, the eggs inside may have been shaken too much, and it may be dried up depending how long the egg case had been on the sand. When I picked it up from her bucket, I noticed it did not smell like many of the unviable ones I have encountered. That smell is usually the telltale sign that the egg case has gone bad. No smell was a very good sign. Upon inspection, I noticed there was a crack in the egg case, and when I lightly shook it, there was no sloshing of liquid inside indicating that it was dried up. Now, this was a bad sign.
I decided to cut a small opening in the egg case to get a better look. Inside there were three small one inch-sized embryos each attached to their own golfball-sized yolk sac. However, they were completely dry, covered with sand, and their little bodies were listless. The liquid probably leaked out of the crack that was found on the outside of the egg case, and this also allowed sand to enter the egg case. I was even more concerned now, and while I started to explain my concern to our volunteer, I started rinsing the sand out with a gentle stream of cold seawater. To our surprise, after about a minute, the little embryos rehydrated and started squirming.
They were alive! Our volunteer had rescued them from completely drying out and dying on the beach.
An acrylic window was put in place where the initial opening was cut, and it has allowed our staff and visitors to watch the embryos develop inside the egg case while on exhibit for the past four months. Three healthy male big skate juveniles were born on April 30, 2019. They are now about 2.5 “ across in size and are currently housed in the estuary exhibit in the Hatfield Visitor Center.
Take a look at this amazing video of this big skate's first moments swimming in the tank.
The common name for the skates that we have at Hatfield Marine Science Center (HMSC) is big skate. The scientific name is Raja binoculata. The Latin word raja means skate or ray, and the Latin word binoculata means two-eyed.
They are identifiable by their large size as adults (up to 6-8 feet across from wingtip to wingtip) and their “eye spots” on their pectoral fins (also known as wings). Big skates are found along the West Coast from Alaska to southern California. They are bottom dwellers and reside mainly in sandy substrate.
They eat crustaceans and bottom fish such as sculpins that are found on or in the sand. They will cover themselves up with sand to rest and hide from their predators. The “eye spots” hidden in the sand can make the big skates appear to be even larger animals than they are with very large heads and therefore can protect them from predators.