Researchers Develop a Key for Identifying Skates from Their
Egg Cases
April 13, 2007
Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334
MOSS LANDING – David Ebert of the Pacific Shark Research Center at Moss Landing Marine Laboratories and graduate student Chante Davis have developed a key for identifying 10 species of eastern North Pacific skates from skate egg cases. All 10 of these species are native to California.
Unlike previous attempts to identify skate egg cases, which females lay on the seafloor, this key is based on characterizations of egg cases removed in utero from skates collected during trawl surveys. “There is no question what species you are talking about when the egg case is removed in utero,” said Ebert, who is program manager of the Pacific Shark Research Center.
Their research has revealed mistakes in published descriptions of skate egg cases for the three species
David Ebert, program manager of the Pacific Shark Research Center
Bathyraja trachura, Raja inornata and R. stellulata. It has also, for the first time, led to descriptions of egg cases of the deep-water skates B. abyssicola and B. microtrachys.
Before, nobody had any idea what these skates’ egg cases looked like, said Ebert, whose research was funded by California Sea Grant and the National Shark Research Consortium.
Their analysis has also confirmed that B. microtrachys and B. trachura are distinct species. Some had considered the skates as synonymous, Ebert said, but their egg cases show otherwise.
“We hope that with better identification of skates, we can begin to evaluate skate ‘takes’ on a species- by-species basis,” he said. Like their cousins the sharks, skates are vulnerable to over-exploitation because they are long-lived, slow-growing and produce relatively few offspring.
Ebert and Davis’ article “Descriptions of skate egg cases (Chondrichthyes: Rajiformes: Rajoidei) from the eastern North Pacific” is published in the Jan. 18, 2007 issue of the journal Zootaxa.
| Species | Egg case (Scale bar 20 mm) | Adult skate |
|---|---|---|
| B. abyssicola |  |
 |
| B. microtrachys |  |
 |
| B. kincaidii |  |
 |
| B. aleutica |  |
 |
To the untrained eye, different species of adult skates look pretty much the same, but their egg cases are obviously different. These differences can be used to identify the parent skate species, as this California Sea Grant research shows. Credit: All photos are from Pacific Shark Research Center at Moss Landing Marine Laboratories.
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