Shiner Surfperch   Cymatogaster aggregata

Shiner Surfperch occur in schools around the floats at the Boston Harbor Marina as well as other floats and docks in protected areas.  Also called the Shiner Perch or Yellow Striped Surfperch, this small member of the Surfperch family only grows to a maximum of 7 inches.  The specimen in the photograph is a young individual about two inches long.  It can be separated from other surfperches by its small size and the presence of three vertical yellow stripes on its sides.

These fish swarm around piling and floats facing into the current snatching small animal prey such as larval crab or shrimp as they drift by.  The fish act like a giant bio-filter that sweeps the water column of the small eatable animals as the current moves by.  As they grow older they also feed on mussels, small crab and, reportedly, algae as well as the filtering appendages of barnacles.  

Surfperch are one of the more commonly seen and caught fish families in the North Pacific.  Eighteen species occur from California to Alaska.  They occur in the nearshore area ranging from low energy areas around docks and kelp beds to more exposed conditions in the coastal surf zone.  Larger surfperch species, such as the Pile Surfperch or Pile Perch (Damalichthys vacca) and the Striped Surfperch, are the species more commonly caught around piling and floats.

Many fish don't protect their young, instead they expel thousands of eggs and sperm into the water column or bury the fertilized eggs in sediment letting the young begin life entirely on their own.  The Surfperch are different.  They retain a few fertilized eggs inside the body where the young develop in a protected condition. These small fish are pregnant for about six months. The young are born in June or July.

See a video of the Shiner Perch filmed by Phil Sconce on YOUTUBE