Giant kelpfish tend to keep their distance. I have many images of them taken from several feet away as they pretend to be part of the scenery. Since they can change colors (red, lime green, yellow and brown) and patterns to match the kelp or algae in which they have chosen to lurk, as long as they remain stationary this camouflage works quite well. It is their surreptitious slinking through the water that brings them to your attention.

Years ago while I was diving off San Clemente Island, however, a biological urge overcame the fishes” reluctance to let me come close. Two golden beauties were performing a mating dance just above some red algae. I had a Nikonos with a 1:3 extension tube and framer. In the past, the only fishes I had been able to coax inside the framer in midwater were ever-bold garibaldis and curious sheephead. But these yellow giants were so engrossed in their courtship that they ignored me and the flash of my strobe, allowing me to shoot portrait after portrait.
All kelpfish can change color to match their surroundings. A study done in 1985 by Carol A. Stepien on the “Long-term color change abilities of juvenile and adult kelpfish” came up with some interesting data. Juveniles can quickly change from green to brown and brown to green. Color changes in adults — mainly females — were more subtle and slower. Male and juvenile kelpfish could not turn red and adult males were also apparently unable to change green. The researchers concluded that, “color change ability and assumption of red color may be governed by sex hormones.” Oddly, the researchers did not mention that both sexes can be yellow and were probably unaware this color phase existed. As well as for camouflage and courtship, the giant kelpfish changes color when defending its territory. I would love to know if yellow is mating garb.
The giant kelpfish diet includes a variety of crustaceans, mollusks and other fishes. They, in turn, are eaten by other fishes, soupfin sharks, Brandt’s cormorants and California sea lions. Spawning occurs year-round. The male establishes the territory and, after the female has laid her sticky brown or red eggs on red or brown algae (not necessarily the one that matches the color of the eggs), stays around to protect them until they hatch in 12 to 17 days. The larvae school in shallow water until they reach a length of about 2.5 inches, when they morph into adults and give up group life to go it alone. Giant kelpfish range from British Columbia to Cabo San Lucas and from intertidal waters to depths of 132 feet.
Giant kelpfish and their close cousins are also called kelp blennies and are members of the order Perciformes, which means perch like. It is the largest order of vertebrates and about 40 percent of all bony fishes — 160 families — belong to it. Giant kelpfish (Heterostichus rostratus) belong to the Clinidae family as does the spotted kelpfish (Gibbonsia elegans). The island kelpfish (Alloclinus holderi) is a member of the Labrisomidae family. Two of the fish pictured here are unidentified. Dr. Love suspects they are also members of the genus Gibbonsia.
All kelpfish have an elongated body and cirri above their eyes. Of the Clinidae family’s 26 genera and 85 species, four live off the California coast. As befits its name, the giant kelpfish is the largest member of its family and can be two feet long. It is also the easiest to identify. The species name “rostratus” means “long-nosed” in Latin and this fish does, indeed have a long nose. It has only one tiny, thread-like cirrus above each eye and the cirrus is difficult to see when the fish is in certain positions. In shape, the body resembles a kelp blade, which is effective camouflage for a fish that hangs around (literally) in kelp. It is the only kelpfish with a forked tail, all of the rest have round tails.
Fishes in the Gibbonsia genera are small. The closely related spotted and crevice kelpfish may be six inches long and the striped kelpfish, nine. All three eat isopods, amphipods, crabs, copepods, shrimps, limpets, mollusks, fish eggs and polychaetes.
The striped kelpfish ranges from Vancouver Island to central Baja, in intertidal waters down to 30 feet. The crevice kelpfish ranges from British Columbia to central Baja, from intertidal waters down to 120 feet, and the spotted kelpfish from Central California to southern Baja, from intertidal waters to depths of 185 feet.
Three members of the Labrisomidae family’s 14 genera and 110 species live off the California coast, according to Dr. Milton Love’s Certainly More Than You Want to Know About the Fishes of the Pacific Coast. The one most frequently encountered by divers is the island kelpfish. They are so common it is almost impossible not to see at least one when diving off the Channel Islands. These little fish with big, curious eyes love to recline in vacant bivalve shells. They are not afraid of divers and are willing photo subjects. The island kelpfish can be five inches long and ranges from San Miguel Island to southern Baja down to depths of 300 feet. It has a three-pronged cirrus above each eye. Island kelpfish can also change colors, but judging from my photos, the results are much more subtle than those of its giant cousins. Both island and giant kelpfish have been observed cleaning other fish.
The author wishes to thank Milton S. Love, PhD, for his help in preparing this article. 
Kelpfish Stats
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Superclass: Gnathostomata
Superclass: Pisces
Class: Actinopterygii
Order: Perciformes
Family: Clinidae: Giant kelpfish, crevice kelpfish, striped kelpfish, spotted kelpfish
Family: Labrisomidae: Island kelpfish
Giant kelpfish (Heterostichus rostratus)
Island kelpfish (Alloclinus holderi)
Spotted kelpfish (Gibbonsia elegans)
Striped Kelpfish (Gibbonsia metzi)
Crevice kelpfish (Gibbonsia montereyensis)