17 Olive rockfish
Distinguishing characteristics. Olive rockfish have a olive-gray or greenish-gray color with a few light blotches showing through on their backs. This color and relatively spineless head (for a rockfish) will distinguish them from all their near relatives, with the exception of the yellowtail rockfish. Yellowtail and olive rockfish are never easy to tell apart either by first-time fishermen or the scientist; olive rockfish normally have nine soft anal rays while yellowtail rockfish normally have eight. However, on numerous occasions both species have one more or one less ray than typical. Although several other equally relative characters also can be used to separate these two species, the fact that olive rockfish are not commonly caught north of Fort Bragg and yellowtail rockfish are not commonly caught south of Morro Bay, is a great deal of help.
Olive rockfish are often confused for kelp bass and vice versa, but a count of the sharp spines in the dorsal fin will help in determining their specific identity. Kelp bass have only 10 spines while olive rockfish have 13.
Distribution. Olive rockfish are a shallow water form that live near the surface in and around kelp beds and near the bottom in rocky areas where the kelp does not form dense beds that reach the surface. Adults have been taken from Crescent City to Cape Colnett, Baja California. The very small young probably are pelagic as are the young of numerous other kinds of rockfish, Adults are especially common around kelp beds where the water is 40 feet deep or deeper. They have been caught at depths, as great as 480 feet.
Life history notes. Olive rockfish are thought to attain a length of about 24 inches and a weight of at least seven or eight pounds, but fish over 20 inches in length are uncommon. Authentic weight and length records are needed for olive rockfish that are longer than 20 inches. The usual size that is caught is 10 to 14 inches long and weighs about two pounds.
An examination of the earbones of these fish indicates that they mature and spawn for the first time when they are three or four years old. The maximum age they attain is not positively known, but it is believed that some olive rockfish are as old as 25 years.
As with other rockfish, fertilization is internal and live young are born. The main spawning season is from December through March and a 20-inch female may spawn as many as 650,000 young during the season. The young are quite helpless for several days after they have been spawned.
The stomachs of a number of olive rockfish were examined and found to contain principally fish. Some crabs, shrimp and squid were also found in these stomachs but were in a definite minority.
Young specimens up to 1.5 inches long have been found in the stomachs of albacore that were caught more than 100 miles offshore.