General Description

Sablefish (Anoplopoma fimbria), also known as black cod, are a groundfish species in the family Anoplopomatidae, which has only one other species, the skilfish (Erilepis zonifer). Sablefish are elongate in shape and are dark gray to black on their upper body with a lighter gray under side. They have two dorsal fins that are well separated which easily distinguish them from skilfish which have two dorsal fins close together. Sablefish have been recorded to reach sizes of 114 cm in length from nose to tip of the tail and a weight of up to 25 kg. An average sized sablefish from the 2010 Southeast Alaska state fisheries is 69.1 cm from nose to fork length and 3.7 kg.

Life History

Growth and Reproduction

Sablefish are a long-lived species with forty-year old fish commonly caught in the commercial fishery. Maturity is reached at around 5 to 7 years; once sablefish reach maturity they spawn annually. They lay 110 eggs per gram body weight, so an average sized sablefish of 3.7 kg will lay about 407,000 eggs. Spawning occurs in deep water (300–500 m) in winter or spring in Alaska, with precise timing dependent on spawning location. Locations of sablefish spawning aggregations in Alaska, and if they aggregate, are unknown.

Eggs develop at depth and larvae in surface waters. Pelagic juveniles drift inshore and remain there until they reach a size of 30 to 40 cm; around age 2 sablefish begin to move into deeper water. They settle into their adult habitat at 4 to 5 years of age, around the time they become mature and capable of reproduction.

Feeding Ecology

Sablefish are opportunistic feeders, consuming a wide variety of organisms. Their diet varies dependent on life stage, geographic location, season, and year. Their diet consists of fish, cephalopods (squid and octopus), and crustaceans. Young of the year (yearling) sablefish have a diet that is mainly euphausidds.

Juvenile sablefish are eaten by a variety of species with adult Chinook and coho salmon as possibly their main predators. A major predator for adult sablefish is most likely sperm whales.

Migration

Federally managed sablefish found in the Bering Sea and in the Gulf of Alaska are considered one population with migration occurring between these regions. In the Gulf of Alaska, small sablefish move westward and large sablefish move eastward. Consequently, large year classes are first noticed in the westward areas. In Southeast Alaska, the Chatham and Clarence Strait fisheries are considered separate populations; however, tagging studies indicate some movement between Chatham Strait and outside waters and between Clarence Strait and British Colombian waters. The degree of migration between inside and outside waters has not been quantified.

Range and Habitat

Sablefish are found along the eastern north Pacific coast from Baja Mexico to Alaska, along the Aleutian Island chain, and the continental slope in the Bering Sea. In the western north Pacific, they occur from Siberia in the Bering Sea to the Commander Islands in Japan.

Adult sablefish are considered to be a groundfish and are associated with the bottom. They occur in deep water, ranging from 150 to 1,500 m (82–820 fm), along the continental slope, in shelf gullies, or in fjords. Sablefish are caught in soft, hard, and mixed substrates; however, they are generally thought to be found in soft substrates. Juveniles tend to be pelagic or semi-pelagic, living in shallower, nearshore waters.

Status, Trends, and Threats

Status

Sablefish abundances in Alaskan waters are relatively low compared to the peak abundances in the late 1980s; however, the sablefish population in federal waters is considered to be neither overfished nor approaching an overfished condition as of 2010. The Chatham Strait population is not considered to be overfished; however the status of other state managed fisheries is uncertain without full stock assessments.

The current stock assessment for sablefish in federal waters can be viewed at the website for the North Pacific Groundfish Assessments.

The U.S. federal longline and the Canadian trap and longline fisheries have been certified as sustainable by the Marine Stewardship Council.

Trends

The domestic sablefish fishery expanded in the early 1980’s. During this time an increase in population abundance occurred due to the exceptional recruitment in the late 1970’s. Catches then fell until 2000 after which there was a modest increase in abundance due to a strong 1997 year class. Since then there has been no evidence of strong recruitment in Alaskan waters.

The federal fishery and state fisheries of Clarence and Chatham Strait began as year round fisheries which shortened down to months and then days in some areas. As a consequence, quota share systems were set up for these fisheries in the 1990’s which increased the fishing season back to several months. In addition, the individual quota share system for federal waters increased catch rates and the spawning potential of sablefish by 9% due to the decrease of harvest of immature fish.

Threats

As of 2010, no sablefish aquaculture operations exist in the United States; however, sablefish farming has begun in nearby British Colombian waters. Sablefish farms which raise fish in ocean pens, raise concerns of possible negative impacts, such as disease, parasites, or genetic threats to wild stocks; habitat destruction of the environment; health risks to consumers; and economic impacts to the fishing industry.

Fast Facts

• Size
  Length up to 114 cm from snout to tip of tail and weight up to 25 kg.
• Lifespan
  Long-lived with maximum ages reported of 55 years in Canada and 94 years in Alaska.
• Range/Distribution
  Deep waters in the western and eastern North Pacific Ocean.
• Diet
  Opportunistic, feeding on both fish and invertebrates.
• Predators
  Juveniles are preyed on by salmon, Pacific halibut, and many other species, and adults likely preyed on by sperm whales.
• Reproduction
  Spawn annually in winter to spring, timing dependent on location. Mass spawners with external fertilization.
• Remarks
  Sablefish fisheries are managed by both state and federal agencies.