Abbreviated Life History of Kelp Rockfish
(Sebastes atrovirens)

Kelp Rockfish; Photo by Steve Lonhart of Simon/NOAA

Atrovirens means black and green in Latin, referring to the coloring of kelp rockfish, which varies in hue from tan to kelp-colored, nearly white to mottled brown, green to black-brown, and even reddish. The red variety was described as a separate species early on. They have a distinct up-turned profile.

Distribution, Stock Structure and Migration

Kelp rockfish live in kelp beds and on rocky reefs, ranging from Timber Cove, northern California to Punta San Pablo, central Baja California. They are most abundant between central California and northern Baja. This species is known to occur at depths up to 190 ft but are most common between 15 and 80 ft, in association with giant kelp. Out of all the rockfish, this species is the most dependent on kelp. Juveniles are occasionally intertidal. Adults are solitary but have been known to form aggregations of 20-50 individuals around oil platforms in the Santa Barbara Channel. Kelp rockfish are residential species, making only rare seasonal migrations in response to storms and changes in kelp density. Within a season, individuals occupy a home range with a radius of about 10 feet.

Age and Growth

Kelp rockfish have been aged to a maximum of 25 years, but few reach the age of 20 years. Males and females grow at about the same rate or females only slightly faster. Both sexes reach similar maximum lengths. Based on a calculated age-length relationship, an 8-inch TL kelp rockfish is approximately 4-5 years old, a 10-inch fish is approximately 10 years old, and 12-inch fish are rare. The largest recorded length for this species is 16.8 inches.

Reproduction, Fecundity and Seasonality

Two central California studies yielded somewhat different estimates of size at maturity. One study shows some females are mature at 6 inches and 3 years, 50 percent are mature at about 7 inches and 3.5 years, and all are mature by 9 inches and 6 years. The other study found the smallest mature female was 8.7 inches and 5 years and the largest immature female was 12.8 inches and 7 years.

Off central California, spawning takes place between February and June, with peak spawning in May. Off southern California, spawning occurs between March and June. Females produce between 10,000 and 275,000 eggs. Females are viviparous and the planktonic larvae are 0.16 to 0.17 inches SL at release. Kelp rockfish settle out of the water column as large larvae, not as pelagic juveniles. The settle into the kelp canopy after 1 to 2 months. As juveniles, they first appear in the kelp beds between April and August. Recruitment to the nearshore area in central California generally occurs during June and July.

Predator/Prey Relationships

Juvenile and adult kelp rockfish are considered searchers with respect to their prey, although adults are also known to ambush their prey. Prominent prey items for adults and juveniles include crustaceans, such as shrimp and amphipods, and small fish, particularly juvenile blue rockfish. The juveniles are prey of birds, pinnipeds, porpoises, lingcod, cabezon, salmon, and other rockfish. Predators of adult kelp rockfish include sharks, dolphins, and seals.

Competition

Blue, gopher, black-and-yellow, and olive rockfishes commonly are found in the same habitat with kelp rockfish. The kelp rockfish is excluded from bottom areas of kelp beds by the territorial gopher and black-and-yellow rockfishes.

Critical Habitat

Kelp rockfish occur in rocky reef and artificial reef areas like oil platforms, but most commonly in kelp beds from the canopy to the bottom. They spend their days drifting motionless within kelp blades, sometimes upside down or resting on them. They are more active at night, leaving the kelp beds to search for prey.

Fishery and Status of Stocks

Kelp rockfish were rarely landed in commercial fisheries until the early 1990s with the rise of the nearshore live-fish fishery. Kelp rockfish are taken in small numbers by commercial hook-and-line and traps for this market. Currently, this species is commonly taken in sport fisheries, such as spear fishing. Their restricted habitat and limited movements make them highly exploitable. Therefore, local depressions probably occur in areas where diving, skiff fishing, or commercial fishing is concentrated. Local abundances have been studied for the kelp rockfish. However there has been no comprehensive stock assessment throughout their range.

Information on this page was originally presented in the Nearshore Fishery Management Plan (these profiles updated July, 2010).

Kelp Rockfish