SABLEFISH

SABLEFISH

LIFE HISTORY

Adult Stage:

Adults are benthopelagic (associated with the bottom, but often farther off the bottom than most demersal species) all along the west coast. They mainly occur at depths < 1500 m and are commonly associatedwith soft bottoms, although they also associate with pinnacles.

Composites: non-rocky shelf, rocky shelf, canyons, continental slope/basin

Spawning Stage:

Spawning occurs from fall through winter in waters from 300-700 m.

Composites: continental slope/basin

Large Juvenile Stage:

Large juveniles are benthopelagic and occur at depths from 100-200 m over soft bottom.

Composites: non-rocky shelf, canyon

Small Juvenile Stage:

Small juveniles are pelagic and occur at depths <100 m in the water column over the shelf and slope, and occasionally in estuaries.

Composites: estuarine, neritic, oceanic

Larval Stage:

Larvae are demersal until the yolk sac is absorbed, then they become pelagic at depths <100 m, up to 370 km offshore.

Composites: neritic, oceanic

Egg Stage:

From fall through winter, eggs occur at depths <700 m in the water column over the continental slope/basin.

Composites: oceanic

Range

Sablefish are very abundant in the north Pacific, from Honshu Island, Japan, north to the Bering Sea, and southeast to Cedros Island, Baja California. Large adults are uncommon south of point Conception [114, 197, 232, 233, 260].

Fishery

Sablefish supports an important commercial fishery off the west coast. Bottom trawling, traps and longlines have been the primary methods of capture. Sablefish are not commonly fished recreationally, mostly because they live at depths too great for most kinds of recreational fishing gear.

Habitat

In the North Pacific, sablefish is considered an inner shelf-bathybenthal species. Adults are found as deep as 1,900 m, but are most abundant between 200 and 1,000 m [31, 151, 215]. In survey data for the North Pacific, nearly all sablefish were taken at depths <700 m [12]. However, off southern California, sablefish were abundant to depths of 1500 m [230]. Spawning takes place at depths greater than 300 m [42, 101, 114, 215].

Sablefish eggs, larvae (after yolk sac is absorbed), and age-0 juveniles are pelagic whereas older juveniles and adults are benthopelagic on soft bottoms. Eggs are usually found deeper than 300 m [114, 151, 215]. Eggs and newly hatched larvae are found in these deep waters from January through March [101, 151, 215, 260]. Newly hatched larvae are demersal until the yolk sac is absorbed [215]. At this time, larvae become pelagic and rise to the neuston layer at the surface. Larvae and young juveniles are found up to 370 km offshore often near drifting kelp [260]. Small (age-0) juveniles inhabit the upper 100 m of the water column [230]. Larvae and small juveniles move inshore after spawning and may rear here for up to four years [42, 215]. Older juveniles and adults inhabit progressively deeper waters.

Sablefish are an important groundfish over soft substrates in deep marine waters [197]. Adults and large juveniles commonly occur over sand and mud [232, 260]. They were also reported on hard-packed mud and clay bottoms in the vicinity of submarine canyons [230].

The preferred salinity range of spawning adults is between 33.7l -34.5l [215, 260], although eggs and larvae were occasionally found in less saline waters [260].

The optimal temperature range for egg incubation was 3.8-6.5EC [215]. The temperature range for larvae and epipelagic juvenile growth was found to range between 5.6-16.5EC and 11.7-16.5EC, respectively [151, 215, 260].

Migrations and Movements

Sablefish are not considered to be a migratory species, although some individuals have been recorded as moving up to 1,700 miles. Sexually mature adults do not undergo any spawning migration [31, 114, 215, 232]. Small juvenile sablefish descend to the bottom during the fall and remain in relatively shallow water for about a year before moving into deeper water [230].

Heifetz and Fujioka [116] reported that small fish move much more than do large fish. Hart [114] recognized localized movement from shallow summer waters to deeper waters in the winter.

Reproduction

Sablefish are oviparous with external fertilization [260]. Spawning occurs annually in the late fall through winter in waters greater than 300 m [114, 260]. Spawning occurs increasingly later in the winter in southern waters [51, 260].

A 53-cm female (5-7 years) may produce 100,000 eggs. A 98-cm female (10+ years) may produce as many as 1.3 million eggs [151, 215, 260].

Growth and Development

Fertilized eggs are spherical and about 1.8-2.2 mm in diameter [151, 197, 215, 233, 260]. Embryonic development is indirect and external; eggs hatch in about 15 days at 6EC [215, 260]. Larvae hatch at about 5 mm and metamorphose at about 38 mm [114, 215, 260]. Juveniles join the benthic community after 1-2 years in a pelagic stage. Females grow faster and larger and live longer than males.

Age and size at maturity are difficult to know because sablefish exhibit such a discontinuous growth rate. It was estimated that 50% of females are mature at 5-6 years and 24 inches, and 50% of males are mature at 5 years and 20 inches. However, McFarlane and Beamish [236] found that tagged sablefish experienced significantly depressed growth, so length-age relationships may not be accurate. The growth rate after reaching maturity slows to 0.17-0.26 cm/year for males, and 0.55-0.66 cm/year for females [233].

Trophic Interactions

Sablefish larvae prey on copepods and copepod nauplii. Copepod eggs provide accelerated growth rates [101, 151, 260]. Pelagic juveniles feed on small fishes and cephalopods, (mainly squids [114, 215]. Demersal juveniles eat small demersal fishes, amphipods and krill [260]. Adult sablefish feed on fishes like rockfishes and octopus [114, 232].

Larvae and pelagic juvenile sablefish are preyed heavily upon by sea birds and pelagic fishes. Juveniles are eaten by Pacific cod, Pacific halibut, lingcod, spiny dogfish, and marine mammals, such as Orca whales [51, 114, 197, 215, 260].

Sablefish compete with many other co-occurring species for food, mainly Pacific cod and spiny dogfish [11].

SABLEFISH

SUMMARY TABLE