MINIMUM SIZE
None
Species · Moonfish
Opah in Southern California, mostly caught by accident
Lampris guttatus
A deep-water fish shaped like a dinner plate, painted silver and red, and the only fish known to be warm all the way through.
TYPE
Opah (moonfish)
SCIENTIFIC NAME
Lampris guttatus
TYPICAL SIZE
60–150 lb
LIVES
Deep, roughly 150–1,000 ft
NOTABLE
Warm-blooded, whole body
CAUGHT
Mostly by accident, on deep gear
opah regulations
DAILY BAG
10, inside the general limit
OPEN SEASON
Year round
Opah has no entry of its own in CDFW's table, so the general finfish limit is what applies: twenty fish in combination, no more than ten of any one species.
14 CCR 27.60(a), as read on October 9, 2026. Limits, seasons and marine protected area boundaries change, so the CDFW ocean sport fishing regulations are the authority, not this page. Check them before you keep anything.
Meet the opah
Almost circular, flattened side to side, silver with white spots and scarlet fins, with a small mouth and a large eye. Nothing else in the Pacific looks remotely like it. It swims by flapping its pectoral fins, more like a bird than a fish.
The warm-blooded part
In 2015 NOAA researchers showed the opah is the first fish found to be warm throughout its whole body. Tuna and some sharks keep their muscles or eyes warm; the opah circulates warm blood through its gills in a counter-current heat exchanger and keeps its heart and everything else above the surrounding water.
Where opah hang out
Deep and offshore, in the cold water below the thermocline, which is why almost nobody sees one. They are solitary rather than schooling. Most Southern California opah come to boats fishing deep for swordfish or on long-range trips, not to anyone targeting them.
On the plate
Opah is several different fish in one body: the loin is pink and firm, the belly is fattier and paler, and the cheek is different again. It is highly regarded, it does not look or cook like anything else on this coast, and for most anglers it is a once-in-a-career fish.
🐟 FUN FACT
Being warm all over means the opah can hunt in cold deep water without its heart slowing down, which is why it can stay below the thermocline and keep chasing squid while most predators have to come back up to warm themselves.
More species
Bluefin TunaYellowfin TunaYellowtailDoradoCalico BassRockfishMarlinWhite SeabassBarred Sand BassCalifornia HalibutCalifornia BarracudaPacific BonitoLingcodCalifornia SheepheadSculpinOcean WhitefishSpotted Bay BassPacific MackerelAlbacoreShortfin MakoCommon ThresherGiant Sea BassSwordfishSkipjack TunaCabezonPacific Sanddab
Heading out for something we do grade?
This is a profile, not a scored species. Fish or Pass grades seven fish across the Bight every day, so if you are going anyway, see what the water is doing for those.