Black rockfish (Sebastes melonops) range from range from Amchitka Island, Alaska in the Aleutian Islands to California. Two weeks ago, I wrote about rockfish in Alaska, and I explained that biologists classify rockfish by dividing them into two groups: pelagic and non-pelagic. Last week, I wrote about yelloweye rockfish, a non-pelagic species. This week, I’ll write about black rockfish, a pelagic species and the most common rockfish in Alaskan waters.
Although not related to the bass family, anglers often refer to black rockfish as black bass because their shape resembles a bass. They have a mottled gray-black body, usually with dark stripes extending from the head to the gill cover. The sides are lighter than the back, and the stomach is pale gray. Black rockfish have a large mouth and a spiny dorsal fin. As with other rockfish, venom sacs lie at the base of each spine. The venom is only mildly toxic to humans, but it does cause pain and can lead to infection. Their light-colored stomach, the lack of pores or a knob on the lower jaw, black mottling on the dorsal fin, and their large mouth which extends past their eyes, are all features which distinguish black rockfish from similar species such as dark rockfish and dusky rockfish. Black rockfish grow to a maximum length of 29.6 inches (69 cm) and weigh up to 11 lbs. (5 kg).
Black rockfish are found anywhere from the surface to 1200 ft. (366 m) deep, but they usually inhabit water shallower than 492 ft. (150 m). They are sometimes seen in large schools at the surface when they are feeding, but they most commonly occur in rocky areas or remain above rocky pinnacles.
Black rockfish are much more mobile than yelloweye rockfish, but biologists in Oregon performed a tagging study and learned the average home range of a black rockfish is only .2 square miles (.55 sq. km). A rockfish sometimes travels outside its home range during the reproductive season or to feed.
Black rockfish reach sexual maturity between the ages of six and eight years. After mating, the female stores the male’s sperm for several months before fertilizing her eggs. Then, between January and May, she releases between 125,000 and 1,200,000 larvae. Black rockfish have a maximum lifespan of fifty years.
Black rockfish feed on zooplankton, crab larvae, and small fish species such as herring and sand lance. Predators of rockfish include sablefish, halibut, other fish species, and seabirds such as pigeon guillemots.
Black rockfish populations in Alaska are considered stable, but fisheries managers set conservative limits on all species of rockfish. Because black rockfish grow and mature slowly, live nearshore, and have small home ranges, they are susceptible to overfishing by sport and commercial fishermen. They are easy to find and easy to catch. Like other rockfish species, they have an unvented swim bladder, and when anglers reel them to the surface, they usually do not survive if released.
As I have mentioned several times over the past few posts, both pelagic and non-pelagic rockfish are highly susceptible to barotrauma, physical injuries due to rapid changes in pressure when an angler catches a rockfish and brings it to the surface. In my next post, I will discuss ways to spare rockfish from barotrauma and methods to protect fragile rockfish populations.
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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.
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