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Thursday, May 3, 2012

Bat Ray...Bat Ray...Bat Ray

(Sung to the tune of the Batman theme song)

The wings (pectoral fins) of a Bat Ray (Myliobatis californica) disappearing below eelgrass (Zostera marina) in Bodega Harbor.

These photos were taken from the Spud Point Marina breakwater on 30 April 2012.  Because the breakwater extends 1300 feet into the harbor, it's a great place to look for marine life.

Bat Rays are found along the Pacific Coast from Oregon to Baja (and around the Galapagos).  They prefer shallow bays and estuaries, and can also be seen in kelp forests and over rocky reefs.  They are sizable fish, with a maximum width from wingtip to wingtip of ~1.8 meters (6 feet) across.

Often your first clue to the presence of a Bat Ray is the appearance of the wingtips flapping above the surface.  They are flexed upward synchronously, and look somewhat similar to the dorsal fins of sharks...but they're paired, and are floppy, more like the fin of an Ocean Sunfish (Mola mola).

Bat Rays feed on invertebrates — e.g., molluscs (clams), crustaceans (crabs, shrimp), and worms.  They use their pectoral fins and prominent snout to dig pits in the mud, exposing invertebrates below the surface.

While observing them recently, it was fun to follow the clouds of sediment in the eelgrass bed as the rays were feeding (it reminded me of watching bubble clouds created by humpback whales).

Bat Rays have unusual teeth they're flattened and hexagonal in shape, ideal for crushing and grinding (imagine trying to break a clam shell in your mouth).  It's worth looking at this picture of a Bat Ray jaw and teeth (scroll down to the 5th image).

1 comment:

Hollis said...

I've seen solitary rays move through the shallow water from the road across the street from the BB Post Office and have been told they have entered the harbor to swarm and breed. Does anyone know when this could be expected?