Plainfin Midshipman      Porichthys notatus

If you turn over a large rock near the low tide line you might find a fish instead of crabs.  Unlike other intertidal fish that use tidepools or hide under kelp when the tide goes out, this fellow takes refuge in the mud under rocks.  A common species, they are seldom seen because of their habitat of feeding at night while burrowing in mud during the day.  In addition the males guard eggs under intertidal rocks during the spring and early summer.

The plainfin midshipman is a member of the Toadfish family, a mostly tropical group, that occur in shallow water and produce croaking sounds with their modified swimbladder (usually by males to attract a mate).  They also have venomous spines on their gill covers.

If you find one take a look at the underside.  There you will find a series of lines made up of white dots called photophores.  These dots reminded an old marine biologist of the rows of buttons on a British Navy midshipman hence the name.  The purpose of the photophores is debated but possibly used as countershading when at depth during the day and to startle predators.

This individual is about 10 inches long and can grow to 15 inches.  Ranging from SE Alaska to the Gulf of California, they can be found from the intertidal zone to depths of 1200 ft where they feed on fish and crustaceans.  They are reported to be important prey for seals and sea lions.