Skate Fish

Generally abundant across the world’s waters, skates are often caught as byproducts by trawlers, so some species are now critically endangered. Skates are also known for having meat that can match a scallop in consistency and flavor when prepared properly. In fact, many Michelin-starred restaurants now feature skate dishes on their menus.

3 Amazing Facts:

• One gigantic liver: The skate fish has one of the largest livers in the animal kingdom. Its liver accounts for a quarter of its body mass. In comparison, the human liver accounts for 2% of body mass. This large liver helps skate fish stay near the ocean floor.
• Thorn-like defense: While stingrays utilize a barbed tail for defense, the body of skates is made of a “thorn-like” material that helps defend them.
• “Mermaid pouches:” Unlike stingrays, which have live births, skates lay eggs. The pouches that contain these eggs are called “mermaid pouches.” It is not uncommon to find them washed up on beaches around the world.

Classification and Scientific Name

Skate fish are cartilaginous fish that are part of the class Chondrichthyes, which also includes sharks, stingrays, and chimaeras. While fish in this class lack bones and thus leave behind limited fossil evidence, it’s believed modern skates began evolving during the Jurassic Period (200 to 145 million years ago).

Over 400 million years ago, the ancestors of all jawed vertebrates, including skates, sharks, and bony fishes, diverged. The first animals to leave the sea and begin walking on land were early tetrapods, which evolved from lobe-finned fishes, a different lineage from skates. Genetic and brain studies show that skates have the makings of a walking animal, and they still “walk” on the ocean floor.

Skate fish belong to the Order Rajiformes, which contains more than 200 species spread across four families. These other families include smooth skates, soft-nose skates, and pygmy skates.

The largest skate fish family is Rajidae, which, as of late 2020, contains 159 described species spread out across 16 genera. An example of a specific skate species’ scientific name would be the big skate, which is named Raja binoculata.

Knowledge of skate taxonomy continues to grow. With these bottom-dwellers often living to depths of up to 8,900 feet, new species and genera may continue to be discovered in the years to come. In fact, during the past decade (2011 to 2020), six new species of skates were discovered.

Species

Most skate fish species have relatively narrow geographic regions. For example, there are eight different skate fish species that are endemic to the water surrounding New Zealand.

Some notable skate fish species include:

• Big skate (Raja binoculata): Found from Baja California to Alaska, the big skate is one of the largest skate species and can reach 8 feet in length and 200 pounds.
• Deepsea skate (Bathyraja abyssicola): A species of skate that lives at the bottom of continental slopes and has been discovered living at depths reaching 8,900 feet.
• Arctic skate (Amblyraja hyperborea): A skate with a wide geographic distribution that lives in cold waters off Greenland and the frigid waters off Antarctica.
• Common skate (Dipturus batis): contrary to its name, it is now critically endangered. Note: Recent research has split the former ‘common skate’ into two species, both of which are threatened.

Appearance

Skate fish species can possess extremely unique body shapes, colors, and even sizes. While big skate have reached 8 feet in length and weigh up to 200 pounds, most skate fish species measure less than 3 feet and weigh in at 10 pounds or less.

With approximately 200 species, skate fish appearance can vary dramatically. The most common color is a “brownish” tint that helps the species blend in with the bottom of the ocean; however, certain skate species have dots or other markings. In addition, skates tend to have a “diamond” or even circular body shape.

Comparison to Stingrays

Skates and rays look very similar, but they have key differences that set them apart into different families.

• Eggs vs. live births: Skates produce eggs that they place in a protective pouch known as a “mermaid pouch”, whereas ray species have live births of offspring.
• Different tails: Rays have sharp barbs at the end of their tails that are used for defense. Skate tails lack this barb, and they instead use “thorn-like” skin as their main defense against predators.
• Dorsal fins: Skates generally have either one or two dorsal fins (fins used for stabilization). Rays either lack dorsal fins or have small remnant fins.
• Size: Skates are generally smaller than rays. The largest ray species — the giant manta ray — can reach a wingspan of 29 feet and a weight of 3,600 pounds. Compare that to the largest skate species, which weighs only about 200 pounds.

Beyond these differences, rays and skate fish also have key differences in their teeth and habitat (skates generally prefer living in deeper waters).

Distribution and Habitat

Skate fish are found in oceans across the globe. Different skate species inhabit environments that range from the shallow mouths of river deltas all the way to outer continental shelves that can reach 8,900 feet in depth.

Skates are found in both cold and temperate climates. Species can be found near the equator all the way to Antarctica in the Southern Hemisphere and Greenland in the Northern Hemisphere. As skate fish lie on the ocean floor, they breathe through spiracles, which are positioned behind their eyes. These specially evolved openings allow skate fish to breathe oxygenated water while buried in sand near the ocean floor.

Reproduction, Eggs, and Lifespan

Skate fish reproduce with eggs that are placed in “mermaid pouches” that are made of collagen proteins and give skate eggs additional protection from predators on the bottom of the oceans. Skate embryos generally live in these pouches for about 3 months (12 weeks) before breaking free. Adolescents grow to about double the size of the pouch (generally about 4″ to 6″) by the time they’re ready to leave its protection.

As skates mostly live in deeper environments and are difficult to observe, it’s a challenge to estimate their exact longevity. However, scientists have placed the common skate fish’s lifespan at 50 to 100 years. Other species may live for shorter periods. For example, estimates of the Winter skate lifespan are listed at about 20 years.

The long lifespan of some skate fish species means it can take 10 or more years to reach maturity, which can make repopulation challenging. Most skate species lay many eggs (common skates will lay approximately 40), but few of these eggs will lead to skate fish that reach maturity.

Conservation Status

Most species of skate fish are considered abundant; however, trawling has led to a decrease in the estimated biomass of a number of skate species.

The common skate is now listed as critically endangered and is offered protection in the European Union. In the United States, the population of Thorny skates is declining, but in 2017, the fisheries service ruled it didn’t warrant protections under the Endangered Species Act. Although the species’ numbers are declining, the final report on its status noted that Thorny skate populations are still estimated to number in the hundreds of millions.

In Cooking

Many skate fish species are abundant and often caught as a byproduct by trawlers. Traditionally, skate fish haven’t been cooked nearly as commonly as other fish species, but their use in cooking is growing.

One of the challenges of cooking skate fish is that, like other cartilaginous fish (like sharks), skates carry urea in their tissues. This can lead to an ammonia-like taste when not prepared properly. Most skates that carry this unpleasant odor are the result of poor storage and mishandling.

Skate is now found on the menu at Michelin-starred restaurants like New York City’s Le Bernardin. In addition, skate fish are seen as a delicacy in other cultures under different preparations. In South Korea, the city of Mokpo has become famous for its skate dishes that have a pungent odor from fermenting the fish.