Brown rockfish are a common nearshore rockfish species in California. They, as their name implies, are brown in color with darker brown mottling.

Distribution, Stock Structure and Migration.

Brown rockfish are found along the Pacific coast of North America from southeast Alaska to Hipolito Bay, central Baja California. They live in shallow waters and bays, and have been found as deep as 420 ft, although they are primarily found in waters less than 175 ft. Sub-adult and adult brown rockfish are residential, although they migrate into deeper water in the winter. Brown rockfish have a home range and tagging studies generally show no movement or movements of less than 2 km, although one tagging study showed a brown rockfish moving more than 50 km.

Age and Growth

Brown rockfish live less than 25 yr, which is a relatively short life span compared to other members of the genus. The maximum size for an adult is 22 inches. There does not appear to be sexual dimorphism between male and female brown rockfish in relation to length, weight, or age.

Reproduction, Fecundity and Seasonality

Male and female brown rockfish mature from 3 to 10 yr of age, measuring 7.5 in. and 15 in., respectively. Half of the population is mature at 5 yr of age, measuring about 10 inches. As with all members of the genus Sebastes, brown rockfish are viviparous. Larvae are released from the female into the pelagic environment in December and January, and may also be released in May and June. They live in the upper zooplankton layer for a month and then metamorphose into pelagic juveniles. The pelagic juveniles spend three to six months in the water column as plankton and micronekton. As they grow older, they settle in shallow water nearshore and then migrate to deeper water. Young-of-the-year fish commonly migrate into bays and estuaries for use as nursery habitat. The use of the bay as a nursery is an uncommon practice for rockfish species. They may remain in the bay around rocks, piers and other structures in areas of higher salinity for one to two years before returning to the open coast. San Francisco Bay appears to be an important habitat for juvenile brown rockfish.

Natural Mortality

A natural mortality rate (M) was calculated to be 0.112 for brown rockfish from Puget Sound, Washington.

Diseases

No information on disease in brown rockfish was found.

Predator/Prey Relationships

As brown rockfish grow, they feed on increasingly larger prey. As juveniles they feed on small crustaceans, amphipods, and copepods, but at approximately five inches shift to crabs and small fish. Birds, dolphins, seals, sharks, lingcod, cabezon, and salmon have been observed to feed on juvenile and adult brown rockfish.

Competition

There was no information available on brown rockfish competitors.

Critical Habitat

Brown rockfish are typically found associated with sand-rock interfaces and rocky bottoms of artificial and natural reefs over a fairly wide depth range, and in eelgrass beds. In shallow waters, they are associated with rocky areas and kelp beds, while in deeper waters they stay near the rocky bottom. Sub-adults migrate into both high and low relief reefs and are strongly residential to their home sites.

Status of Stocks

Brown rockfish have long been an important component of the marine recreational fishery and a relatively minor but important component of the nearshore commercial fishery in California, especially north of Point Conception. While there have been studies of local abundance in certain coastal areas and within bays, the population size and structure of this species has not been comprehensively assessed.

The brown rockfish has been identified as a species vulnerable to severe localized depletions in other areas; in Washington state, the Puget Sound stock of brown rockfish was recommended for listing as a threatened species in 1999.