Long, slender fish with long, continuous dorsal (top) and pelvic (bottom) fins.
Olive brown to bronze to dark iridescent purple coloration on back, paler coloring on sides, yellow on belly.
White space under eyes with a black crescent below.
Hundreds of photophores (light-emitting organs) line the underside of their head and body to attract prey.
Can be up to 15 inches long.
Sitka, Alaska to Magdalena Bay, southern Baja California, Mexico.
Two populations: one Oregon northward and one San Francisco southward.
Live from the intertidal (area of shoreline covered at high tide and uncovered at low tide) to the deep sea.
Live over sandy and muddy bottoms.
Males make nests under large rocks or seaweed in intertidal zone, and are sometimes fully out of the water.
Adults are often in deep water but travel to the shallow intertidal in spring and summer to breed.
Males produce a loud droning hum to attract females to their nesting site under large rocks and seaweed.
Females will lay her orange eggs in the nesting site and then leave.
The males will fertilize the eggs and tend to the nest.
The eggs will hatch in approximately four weeks into miniature versions of the adults.
In another 4-6 weeks, the juveniles will leave the nest and swim into the deep ocean.
Crustaceans and other fishes.
Seals and sea lions.
For years, residents of houseboats in Sausalito, California complained of a noise on summer nights that was so loud that they often couldn’t sleep. The droning hum sounded like it was manmade, like a group of motorboats or large submarines, but it was actually the vocalizing hum of male plainfin midshipman! They make the noise by contracting the drumming muscles on their swim bladder.
Plainfin midshipman can make other noises. They can not only hum, but can also grunt and growl.
When adults are out of the water, they can breathe air!
Hear a Midshipman
Sources: Discovery of Sound in the Ocean; FishBase; American Fisheries Society; Elkhorn Slough National Estuarine Research Reserve