Latin name

Beringraja binoculata

Identification

The pectoral fin discs of the big skate have a flattened diamond shape, with their width slightly exceeding their length; the snout is elongated and pointed. The eyes are small and located just in front of the large spiracles. The teeth are small with pointed cusps; the upper jaw has 24–48 teeth arranged in rows, while the lower jaw has 22–45. Juveniles have smooth skin, whereas adults possess small spines on the dorsal surface and the upper half of the snout between the gill slits, as well as on the ventral half of the body. It has two or three thorns on the middle of the back, a row of 12-55 (usually 13–17) thorns along the midline of the tail, and an interdorsal thorn. Some older individuals have a thorn above each eye.

Features of Fish Fins

Two small dorsal fins are located on the tail, an anal fin is absent, and the caudal fin is reduced to a simple fold. Each pectoral fin has a weak indentation.

Fish Coloration

The dorsal side of the big skate is colored in brown, reddish-brown, olive-brown, or gray, with scattered small white spots or occasional dark spots. Two large dark spots with light edges are present, one on each "wing." The ventral side is white, sometimes with dark dots or spots.

Distribution

A widely distributed species in the northeastern Pacific Ocean, from the eastern Bering Sea and Aleutian Islands in the north to Cedros Island off Baja California in the south. It is rare south of Point Conception in California. It is an abundant species off the coast of British Columbia.

Habitat

Within its noted depth range of up to 800 meters, these skates are rarely found deeper than 120 meters. Their occurrence progressively increases closer to shore in the northern part of their range. Off the coast of British Columbia, they prefer depths of 26 to 33 meters and temperatures of 7.6 to 9.4 °C. They inhabit coastal bays and estuaries over the continental shelf, usually over sandy and muddy bottoms, but are occasionally found over coastal kelp beds.

Size

The maximum recorded length is 2.4 m (7.9 ft), and the maximum recorded weight is 91 kg (201 lbs), although they typically do not exceed 1.8 m (5.9 ft).

Behavior

Underwater observations show that big skates typically bury themselves in the substrate, with only their eyes remaining visible.

Food and Feeding Habits

They feed on polychaete worms, mollusks, crustaceans, and small benthic fish. The proportion of polychaetes and mollusks in the diet of juveniles is somewhat higher than in adults. The broadnose sevengill shark (Notorynchus cepedianus) is a known predator of these skates. The eyespots on the wings are believed to serve as a distraction for predators. Their egg cases can be consumed by juvenile northern elephant seals (Mirounga angustirostris). The skates are parasitized by copepods (Lepeophtheirus cuneifer).

Reproduction

Egg cases are laid in pairs on sandy or muddy bottoms. There is no distinct spawning season, and egg-laying occurs year-round. Females may use various spawning beds, but most eggs have been found in certain localized areas. The young hatch after 9 months, measuring 18–23 cm (7–9 in).

Females reach maturity at 12–13 years of age and a body length of 1.3–1.4 m (4.3–4.6 ft), while males mature between seven and eight years of age at a length of 0.9–1.1 m (3–3.6 ft). The growth rate of skates in the Gulf of Alaska is comparable to that off California but differs from the growth rate off British Columbia. The lifespan off Alaska is up to 15 years, while off British Columbia it is up to 26 years.

Fishing

Big skates are frequently caught by recreational anglers, who typically release or discard them. These skates adapt well to captivity and are often kept in oceanariums and public aquariums. It is one of the most important commercial skates harvested off California, although it is of minor importance compared to other commercial species. They are usually taken as bycatch in bottom trawl fisheries.

Relationship with Humans

The pectoral fins are sold as "skate wings" and are consumed boiled or fried. In the 1990s, the market price for skate wings rose to $0.40–$1.00 per pound, causing skate landings in California to immediately increase tenfold, as the trawl fishery began marketing its bycatch. In 2003, a targeted fishery for the big skate and the longnose skate (Raja rhina) was opened in the Gulf of Alaska. The consequences of this increased exploitation are unknown, but due to this species' low population growth rate, the International Union for Conservation of Nature has assessed the big skate as Near Threatened.

Interesting Facts

It is an oviparous species with internal fertilization. Unlike other skates in the family Rajidae, the egg cases of the big skate contain more than one embryo. Egg cases washed ashore by storms or tides are called "mermaid's purses." The egg case of the big skate is the largest among skate species, measuring 23–31 cm (9–12 in) in length and 11–19 cm (4–7 in) in width. The cases are oblong with a domed upper surface and an almost flat ventral surface. Parallel ridges are visible on the sides of the case, becoming concave towards the center. Each end of the case has four blunt, broad horns, with the posterior pair being longer than the anterior pair. Each case can contain from one to seven eggs (typically 3–4).