Aquarium of the Pacific - Online Learning Center - Species Print Sheet
California halibut are flatfish that usually inhabit relatively shallow water. They have been described as a nearshore waters species and also as an estuarine-inner shelf species due to their use of estuarine wetlands as nurseries. Although members of the left-eyed flounder family, they are predominately right-eyed. Targeted by commercial fisheries and recreational fishermen, common names used by these groups are fly swatter for small halibut and barndoor for large halibut.
Quillayute River, British Columbia, south to Magdalena Bay, Baja, California Most common south of Bodaga Bay, California. There is an isolated population the northern Gulf of California. The California stock is divided into two populations, southern California and central California.
Adult halibut prefer nearshore waters with soft flat bottoms of sand or mud. They are also found in kelp beds and occasionally in rocky areas. Although they may be found in ocean waters as deep as 183 m (600 ft), they more commonly inhabit water at depths from outside the surf line to 60 m (198 ft)
California halibut are flatfish. They have an oblong, compressed body with a distinctive high arched lateral line above the pectoral fin. They have a relatively small head but their twisted mouth is large with many sharp conical teeth. Their eyes may be on the right or left side of their head.
Adults are usually uniformly brown to brownish-black on the eyed (top or dorsal) side but occasionally they may be mottled and or have some whitish spots. The non-eyed (ventral or bottom) side of these fish is usually white to creamy- white, and may have some mottling. This coloration, dark on the top and white on the bottom is called countershading. It serves to decrease the visibility of the fish to predators. When viewed from below, the white side of the fish blends into the lighter water above. When viewed from above, the dark side blends into the darker water or substrate below the fish.
Usually 38-76 cm (15-30 in) in length
Diet and Feeding
Adult halibut feed primarily on Pacific sardines, northern anchovy, other small nearshore fish species that swim in the water column, and squid. Juveniles inhabiting bays and estuaries eat crustaceans including copepods and amphipods.
California halibut are ambush predators. They usually hunt during the day but will also do so at night. When foraging, they typically lie partially buried in the sand or mud in a stationary position, watching prey until the prey comes to within striking distance. They then dart forward and slightly upward to seize the prey. If the lunge is initially unsuccessful, the halibut may vigorously pursue prey all the way to the surface of the water. Large individuals have been observed jumping clear of the water as they make passes at schools of fish.
Males may mature as early as two or three years of age; females not until four or five. Fertilization is external. Spawning season is February through September, peaking April through July. During this time spawning adults leave deeper waters for shallower inshore areas where broadcast spawning of sperm and eggs takes place. The number of eggs released by the female at one time is dependent on her size. At five years of age about 300,000 eggs are spawned. Larvae free drift for a few weeks before settling to the floor of bays and wetlands that may serve as nurseries. Here they metamorphose to a juvenile form.
Halibut are bottom dwellers, occasionally approaching surface waters when feeding. They are primarily ambush predators that lie quietly on the bottom, often with only their mouth and eyes visible, waiting for small prey to swim within striking range.
While most flatfishes are either right or left eyed, California halibut can be either. When born, halibut larvae look like most other fishes–with one eye on each side of the head. After about five days to several weeks, they move down the water column to settle on the floor of bays and wetlands where metamorphosis begins to adapt them to the life style of a bottom dwelling flatfish. Over a period of 20-29 days, one eye migrates across the head to join the other eye so both are on the same side of the fish’s head, most often in the case of California halibut, on the right side. The body turns sideways to the flatfish form. The mouth twists; and a color change occurs.
The basic color of these fish is much like that of the substrate they rest on. When their bottom habitat changes, they change their dorsal side coloration, effectively camouflaging themselves.
Maximum life span is about 30 years
Predators of this species include bottlenose dolphin, angel sharks, Pacific electric rays, sea lions, and humans. California halibut are a target fish both commercially and recreationally. While the California Department of Fish and Wildlife does not have a management plan in place for the fisheries, catch is regulated. These regulations cover season, size, and gear used. Commercial fisheries use gill nets, trawl nets, and hook and line. Recreational fishermen use hook and line and divers’ spears. The legal size for a halibut catch to be kept is 56 cm (22 in).
While the central California population appears somewhat stable, the southern California population has declined at least 14% since 1999. Overfishing may be a factor but scientists believe the most severe impact is caused by coastal development that has resulted in a severe loss of the wetland habitats that serve as nurseries where juvenile halibut develop into adult fish.
In Pacific halibut (Hippoglossus stenolepis), the jaw extends only to the front edge of the eye. In California halibut it extends beyond the eye. Pacific halibut have more than 80 soft dorsal rays and the eyes are always on the right side of the head. California halibut have less than 77 soft dorsal rays and the eyes may be on the right (60%) or left side (40