Robert there is the California Butterfly Ray which is fairly common and the Diamond Stingray which is fairly rare, but I think the fish you describe, especially given the area, is the round stingray. Some round stingray are so dark they are almost black. I have only caught one butterfly ray (Ocean Beach Pier, August 1991) and one diamond stingray (Coronado Ferry Landing Pier, July 2007).
California Butterfly Ray
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California Butterfly Ray
Species: Gymnura marmorata (Cooper, 1864); from the Greek word gymnos (bare) and the Latin word marmoratus (marbled).
Alternate Names: stingray, butterfly stingray, eagle ray, diamond ray or butterfly ray. In Mexico it’s called raya mariposa de California. In Denmark it’s apparently called Californisk sommerfuglerokke; not sure why since it isn’t found in that country.
Identification: Butterfly (diamond) shape with the disk almost twice as wide as long. Tail short with a small sting at its base. Brown to gray above with darker and lighter mottling; white below.
Size: Width to 5 feet. Most caught from piers are 2-3 feet wide.
Range: Paita, Peru, and the Gulf of California, to Point Conception.
Habitat: Common in shallow bays and along sandy beaches. Recorded to a depth of 308 feet.
Piers: Most commonly caught at piers in the San Diego area. Best bets: Ferry Landing Pier (Coronado), Embarcadero Marina Park, Imperial Beach Pier, Ocean Beach Pier, Crystal Pier, and Oceanside Pier. (Quite a few show up in the scientific records as being taken from the Scripps Pier in La Jolla. First recorded there in 1945.)
Shoreline: An occasional catch by southern California surf fishermen.
Boats: An inshore species rarely taken from boats.
Bait and Tackle: Light to medium tackle is common; size 4-2/0 hooks with cut bait (anchovies or squid), ghost shrimp, clams and bloodworms all equally productive.
Food Value: Very good if cleaned quickly and kept chilled. The flesh is mild-flavored and the texture is firm. I caught a good-sized butterfly ray one day while fishing at the Ocean Beach Pier, put it on ice before returning north, and it turned out to be delicious when fried up three days later.
Comments: An incidental catch for most anglers; few anglers target them as a species. However, it is apparently a favorite ray for “eating” in Mexican waters with its white flesh considered superior to that of other rays.
Diamond Stingray
This large beast was taken by the San Diego crew in 2006 (and I wish I could remember all the names)
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Diamond Stingray, Dasyatisvdipterura, found at least from Malibu south to Chili. Common from San Diego Bay south. Length to 78.7 inches, width to 48 inches; surf zone down to 355 feet.