The big skate is the Pacific's largest skate — a 2.4-metre flatfish-eyed predator of the kelp-edge sands, famous for giant mermaid's-purse egg cases with twins inside.
Walk any storm beach from Alaska to Baja after a winter blow and you will eventually find one: a leathery black capsule the size of a paperback, horned at the corners, washed up among the kelp wrack. Beachcombers call it a mermaid's purse. It is the egg case of the big skate (Beringraja binoculata), and it is one of the most generous packages any fish puts to sea — a single case often holding not one but several embryos, jostling inside like passengers in a tiny lift. Meet the largest skate in North American waters.
| Scientific name | Beringraja binoculata (formerly Raja binoculata) |
| Family | Rajidae (skates) |
| Maximum size | To about 2.4 m long and over 90 kg; the largest skate in the eastern Pacific |
| Range | Eastern Pacific: the Bering Sea and southeast Alaska to central Baja California |
| Depth | Shallow subtidal to roughly 800 m; commonest in shallow soft-bottom bays and kelp-edge sand |
| Diet | Benthic invertebrates — crabs, shrimp, worms, clams — plus small fishes |
| Reproduction | Huge leathery egg cases, each typically containing multiple embryos (3–4, sometimes 7) |
The big skate is a classic diamond — a flattened body with triangular pectoral wings, a pointed snout, and a modest tail armed with small thorns. The back is brown to grey, scattered with dark spots. But the field mark is the name: binoculata, "two-eyed." Each wing carries a large dark eyespot ringed with pale, sitting like a false eye on the shoulder. Flashed suddenly, the spots draw a predator's strike to expendable wing rather than to head — an old trick performed at unusual scale.
Size is the other giveaway. Most skates that a diver or angler meets top out well under a metre; a big skate at full stretch approaches 2.4 metres from snout to tail tip and can exceed 90 kilograms — broad enough to pass for a small scallop dredge gliding over the sand. Among the eastern Pacific skates it is the giant, and among the Pacific's flat hunters it is rivalled for sheer presence only by the bat ray, which is a true ray (and, unlike a skate, carries a sting).
Under the wings the big skate is built like the rest of its family: a mouth full of small pavement teeth for crushing, spiracles behind the eyes for breathing while buried, and a habit of semi-burial in sand that will hide a two-metre animal from a diver's eye to within one slow blink of movement.
Big skates are habitat generalists within one rule: soft bottom, cool water. They live on sand and mud flats, in bays, on the open shelf — and, most importantly for our work, along the sandy aprons that run beside and between rocky kelp reefs. That marginal sand is a hunting corridor. The skate cruises the edge where sand meets rock, taking crabs and shrimps that drift out of the kelp's shadow, and pressing down into the sediment for whatever lies just below it.
The kelp forest food web runs on exactly these exchanges across the sand-rock boundary. What grows on rock feeds the sand; what hunts on sand presses on the reef. The big skate sits on the sand side of that treaty, alongside its cousin the leopard shark and the bat ray, all three of them pressing benthic prey from the fish side. Remove them — as trawl and gillnet bycatch has thinned them locally — and the sand-reef interaction shifts in ways the current monitoring literature is only beginning to map. It is one of the reasons Tidewright's survey frames take pains to log elasmobranchs, not just the photogenic fish: in a kelp forest food web, the flat hunters on the apron are load-bearing.
Skates are the egg-laying branch of the flat cartilaginous fishes — sharks and rays mostly bear live young, but skates armour their embryos in keratin cases and lay them in pairs, one from each uterus, on soft sediment. The big skate's case is the largest in its range, and it holds a biological surprise: multiple embryos per capsule, three or four in a typical case and up to seven recorded. Each embryo has its own yolk but shares the case's capsule space, hatching out through slits at the capsule ends after as long as nine months of development.
The resulting beach record is both conspicuous and confusing to the finder. A big-skate mermaid's purse is big, dark, and solid: rectangular, full of last year's hatchlings' escape slits or, rarely, still heavy with its cargo. Cases turn up on beaches from the Gulf of Alaska to Baja, and beach naturalists can often date a find by the algal growth on the case: a clean black capsule is fresh, a greened and barnacled one has been at sea for months.
The reproduction is slow in every direction — slow to mature, slow embryos, good-sized clutches at modest frequency. It is the classic elasmobranch life-history bet, and it makes the big skate the kind of animal that a population dip hurts for a generation.
The big skate's modern history is the bycatch story of the whole Pacific groundfish enterprise. Through the mid-twentieth century, skates were caught in bottom trawls and discarded in quantity; by the late twentieth, the same skates had begun to look commercially interesting as a wing-meat product, so they shifted from discarded to landed — and the assessment question shifted too. On the US West Coast the big skate has been managed within the groundfish complex, with assessments finding the body of the stock, at time of writing, above its overfished threshold and rebuilding or holding in the main. In Canada and Alaska its story is patchier, shorter, and less well-counted.
The honest summary is that big skate status varies sharply by jurisdiction and by decade. The global red-list assessment has treated it as Near Threatened, the US federal status as not overfished in recent assessments, and the practical reality in any given bay depends entirely on the local trawl footprint and the local observers. It is a species for which careful fishery management actually works — and one for which warming water compresses habitat in exactly the shallow zone the juveniles use.
Divers meet big skates most reliably over sandy bottom near rocky reef in the cooler half of the range: Puget Sound, the inside waters of British Columbia, the sand channels of Monterey Bay, the flats around the Channel Islands. The classic encounter is not a chase; it is a slow fly-past of a winged shape across sand at dusk. They are also a regular bycatch-and-release fish for pier and surf anglers on the US West Coast, and the current consensus among fishers and agencies alike is to return them promptly, unhooked, flat to the water.
For the underwater photographer they are one of the easier elasmobranchs to approach: settle, don't block the light, and let the animal close the distance. A good big-skate shot, like a good encounter with the bat ray, is about posture rather than pursuit. The species is, in short, the kind of neighbour that rewards the habits patient divers already have.
Both are flattened cartilaginous fishes, but skates lay eggs in tough cases, have fleshier tails with small thorns (no sting), and generally have pointier snouts. Rays mostly bear live young, and many carry one or more venomous tail stings. The bat ray gliding beside a big skate is the classic side-by-side comparison.
Essentially no. There is no sting; the risks are the thorns and the sheer mass. Treat any two-metre animal with space and calm, and the big skate is among the most benign large elasmobranchs a cold-water diver can meet.
It is the egg case of a skate (or of some sharks): a leathery keratin capsule that protects the embryo on the seafloor. Big-skate purses are recognisably large and multi-horned, and a single one may hatch three to seven young.
Yes — skate wings are eaten, and the big skate has supported a small commercial and recreational fishery on the US West Coast. Because it is slow-growing and because status varies by area, the responsible choice is to check the current local management advice before keeping one, and to return them as a default.
Cold Pacific sand next to rock, in the shallower half of the depth range: Puget Sound, British Columbia inside waters, Monterey Bay, and the Channel Islands sand channels. Dusk is your friend. Lie still on the sand and let it come to you.
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