 Plainfin Midshipmen (Porichthys notatus)
 Distribution of plainfin midshipmen in San
Francisco Bay
Plainfin midshipman are demersal marine
fish found in the Gulf of California and from Gorda Bank, Baja
California northward to Sitka, Alaska.
They reach a maximum length of 380 mm TL and inhabit depths from
intertidal to 3280 m. They are trapped commercially
in San Francisco Bay for striped bass bait, and are a seasonal nuisance to
houseboat owners in Richardson Bay because the humming sound males make to
attract females during the spawning season is audible, especially at night!
Spawning takes place from April through August in
San Francisco Bay. Males excavate nests from under solid structures
in the intertidal zone; females apparently enter the nest to deposit demersal
adhesive eggs which the male fertilizes and subsequently guards until the larvae
are free swimming. Free swimming larvae rapidly develop into juveniles
and settle to the bottom. Spawners of both sexes are believed to die after spawning.
Both juveniles and adults bury themselves in soft bottoms during the day and move
into the water column at night to feed. Juveniles have a tolerance for lower
salinities and are occasionally found in freshwater in the lower Sacramento-San
Joaquin Delta.
Annual abundance indices for young-of-the-year
plainfin midshipmen are generated from the San Francisco Bay Monitoring Program
using otter trawl data.
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