The Gadiformes are an order, or large group of related fishes. Today, they include about 630 living species of cods, hakes, rattails, and their relatives.
The familiar Atlantic Cod is only one branch of this much bigger family tree!
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Beyond Cod
Cod are well known for their culinary use. Buttered, fried, seared, or baked, their white, flaky meat is a favorite seafood in restaurants and homes around the world. But cod and their relatives (collectively the codfishes) such as Atlantic Cod, Pollock, and Haddock are much more than food. For centuries, they have supported fisheries, coastal economies, and livelihoods worldwide, becoming deeply woven into the history and culture of many societies.
Their importance extends beneath the surface. In marine ecosystems, codfishes are both predators and prey, helping connect food webs. Their wide-ranging diets can include squid, fishes, shellfish, sea stars, and crustaceans such as crabs and lobsters. And the familiar cods we know are only part of a much bigger story. Cods are members of the Gadiformes, a diverse group of fishes found from shallow coastal waters to the deep sea, and from pole to pole.
Who are the Gadiformes?
Credit: Joachim S. Müller/Flickr (CC-BY-NC-SA 2.0) 
The Father of Gadiformes
Credit: Photo Courtesy A.V. BalushkinAnatoly N. Svetovidov (1903–1985)
Much of the foundation for how scientists classify cods and their relatives traces back to Soviet ichthyologist Anatoly N. Svetovidov. His landmark 1948 study on Gadiformes synthesized their anatomy, classification, evolution, and distribution, and his framework influenced gadiform systematics (or the scientific study of how living organisms are identified, named, classified, and related to one another through evolution) for decades. Later studies still routinely refer to Svetovidov’s work.
The story did not stop there. Daniel Cohen, Tadashi Inada, Tomio Iwamoto, and Nadia Scialabba produced the influential 1990 FAO Gadiform Fishes of the World, bringing together worldwide knowledge of cods, hakes, grenadiers, and their relatives in one reference document.
Today, gadiform systematics continues to evolve as ichthyologists combine knowledge learned from museum specimens, anatomical studies, fossils, and genetic data to refine and build upon the classifications developed by earlier generations.
In this photo Svetovidov stands to the right of his mentor.
Deepest-Living
Credit: NOAAAbyssal Grenadier — Coryphaenoides armatus
Recorded to about 17,000 ft (5,180 m)
Far below the ocean surface lives the Abyssal Grenadier, a rattail adapted to a world of darkness, cold, and crushing pressure. Food can be scarce at these depths, so it moves slowly and conserves energy while searching for its next meal.
Young fish feed largely on bottom-dwelling invertebrates, while adults prey on fishes, squid and other cephalopods, and sea urchins. Its ability to find food in such an extreme environment helps make the abyssal grenadier one of the great deep-sea specialists of the gadiformes.
One of the Shallowest-Living
Credit: Jujurenoult via Wikimedia CommonsFive-bearded rockling — Ciliata mustela
Intertidal zone — nearly 0 m
In the rocky shallows of western Europe lives the five-bearded rockling, a small cod relative adapted to life where the tide moves in and out each day. It shelters beneath rocks, in crevices, and under overhangs, and often stays close to a familiar “home” area.
It has five barbels: four around the snout and one on the lower jaw, which gives the species its name. It feeds mainly on crabs and other crustaceans, marine worms, and mollusks, and occasionally on small fish.
Largest
Credit: Joachim S. Müller/Flickr (CC-BY-NC-SA 2.0)Atlantic Cod — Gadus morhua
Up to ~ 6.5 ft (2 m) and ~212 lb (96 kg)
The Atlantic Cod is one of the giants among the gadiforms. Large individuals can reach roughly six feet (2 m) in length and nearly 200 pounds (100 kg), making them incredible predators of fishes, crabs, shrimp, squid, mollusks, and other animals living near the seafloor.
Few fishes have shaped human history as profoundly as cod. As Mark Kurlansky recounts in Cod: A Biography of the Fish that Changed the World, Basque fishers were among the early Europeans to build a major trade around Cod, and by the 1500s they were crossing the Atlantic to fish the rich waters around Newfoundland. Cod later helped sustain ports and coastal communities throughout the North Atlantic and became deeply embedded in regional economies, diets, and cultures.
Sadly, intense fishing drove major declines in Atlantic cod during the late twentieth century, and several stocks remain far below their historical levels today.
Smallest
Credit: Saksena & RichardsStellate Codlet — Bregmaceros houdei
Up to 0.6 in (~1.6 cm)
At little more than half an inch long, the Stellate Codlet is one of the tiniest members of the gadiforms—about 125 times shorter than the largest Atlantic cod! It lives in tropical waters of the western Atlantic, including the Gulf off Texas and the Caribbean Sea.
Despite its tiny size, it has an unmistakably unusual body plan. Like other codlets, it carries a single greatly elongated dorsal-fin ray on top of the head. Several pelvic-fin rays are also exceptionally long and can fold along the body. Codlets are small pelagic fishes of tropical and subtropical seas, occupying habitats from shallow coastal waters to the mesopelagic zone.
Most Commercially Important
Credit: By George Berninger Jr. - Own work, CC BY-SA 4.0Alaska Pollock (aka Walleye Pollock)— Gadus chalcogrammus
Alaska Pollock supports one of the largest fisheries on Earth—and its Bering Sea fishery is often considered a model of science-based fisheries management. Huge schools are harvested across the North Pacific, especially in the Bering Sea and Gulf of Alaska.
Even if you have never ordered Alaska Pollock by name, you have probably eaten it. Its mild white meat is used in fish fillets, fish sticks, and surimi—the ingredient behind much of the imitation crab sold around the world. Pollock is also processed into roe, fish meal, and oil, meaning remarkably little of the catch goes to waste.
In 2023, 1.43 million metric tons of pollock were harvested for a total worth of $1.7 billion. Pollock's worth extends beyond the dock, supporting nearly 17,000 jobs through affiliated industries like processing plants and shipping, among others.
Oldest Known Fossil
Credit: Modified from Schwarzhans et al., 2022“Protocodus”
~63–62 million years old
The oldest known gadiform represented by a skeleton is “Protocodus,” an ancient cod relative discovered in Paleocene rocks aged about 63 million years old from western Greenland. It lived only a few million years after the asteroid impact that ended the age of dinosaurs.
But the gadiform story goes back even further. Fossils reveal that the evolutionary history of cods, hakes, rattails, and their relatives stretch back to the time of the dinosaurs. Researchers identified tiny fossil otoliths—the mineralized “ear stones” fishes use for balance and hearing—from Late Cretaceous rocks as belonging to gadiforms. These fossils show that the lineage was already swimming in the oceans before the mass extinction of dinosaurs 66 million years ago. This photo shows otoliths from many ancient gadiforms.
The Weirdest
Credit: JAMARCInflated whiptail — Macrouroides inflaticeps
Found from 2,450 to 13,120 ft (~750 to 4,000 m) depth
With its enormous balloon-like head, tiny eyes, short trunk, and long strap-like tail, the inflated whiptail looks unlike almost any other gadiform. It also lacks pelvic fins, a chin barbel, and a light organ, and has a small swim bladder.
This bizarre deep-sea fish can grow to nearly 48 cm (19 in) long and has been recorded across tropical regions of the Atlantic, Indian, and Pacific oceans.
At the Smithsonian
Credit: Courtesy Adela Roa-VaronBehind the exhibitions at the National Museum of Natural History are thousands of cods, hakes, rattails, and their relatives collected from oceans around the world. The gadiforms collection includes more than 16,000 individual fishes, preserving a remarkable record of the group’s diversity. Some of these specimens have been at the Smithsonian for more than 170 years, with collection records dating back to the early 1850s.
Among them are hundreds of type specimens—the official reference specimens scientists use when a new species is named and described. Together with tissues, skeletons, radiographs, and other preserved material, these specimens allow scientists to revisit species described decades ago and ask entirely new questions using modern tools such as genomics (an organism’s complete genetic material) and 3-D imaging.
In this photo, Smithsonian scientist Adela Roa-Varón, who has studied the gadiforms for more than 15 years, examines a specimen from the museum’s collection.