The aptly named big skate (Raja binoculata) is the largest skate in the waters off North America. Big skates range along the Pacific coast from Alaska to Baja California. They inhabit a variety of habitats, from bays and estuaries to the continental shelf. They prefer sandy or muddy bottoms and seem to prefer depths shallower than 390 ft. (120 m). They inhabit shallower water in the northern part of their range.
The largest big skate ever captured measured 7.9 ft. (2.4 m) in length, but they typically reach a maximum of 5.9 ft. (1.8 m) in length and weigh as much as 201 lbs. (91 kg). An average big skate weighs less than 110 lbs. (50 kg).
A big skate has a diamond-shaped, flattened pectoral fin disk. It has a pointed snout, and the eyes are small and sit just ahead of the spiracles. The tail has two small dorsal fins but no anal fin, and the caudal fin is only a simple fold. A juvenile has smooth skin, but an adult’s skin has small prickles on the dorsal surface, the underside of the snout, between the gill slits, and on the abdominal region. An irregular row of approximately 33 middorsal thorns runs down the back and tail to the first dorsal fin. A single thorn protrudes from behind each eye. The back of a big skate ranges in color from mottled reddish-brown to olive-brown to grey, and it is covered with small, pale white spots or dark blotches. The ventral surface ranges from white to gray.
A large dark spot with pale borders appears on each wing of a big skate, and biologists suspect these “eyespots” appear to predators as the eyes of a much larger animal, making a shark or another predator much less likely to attack the skate.
A big skate camouflages itself by partially burying its body in the sand and silt on the seafloor. Between its submerged position and its mottled coloration, a skate appears nearly invisible to predators and prey. When partially buried, it breathes with the aid of the spiracles on the top of its body. It takes water in through these spiracles and pushes it out through the gills on its dorsal surface.
Big skates differ from Alaska skates in that their egg cases may contain as many as seven eggs each. The big skate produces the largest egg case of any skate species, measuring 9 to 12 inches (23-31 cm) long and 4 to 7 inches (11-19 cm) wide. Big skates have a maximum lifespan of 26 years, but most big skates in Alaska don’t live past 15.
Robin Barefield is the author of four Alaska wilderness mystery novels: Big Game, Murder Over Kodiak, The Fisherman’s Daughter, and Karluk Bones. Sign up below to subscribe to her free, monthly newsletter on true crime and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.
Listen to my podcast about true crime and mystery in Alaska.
