15 Cod Facts You Didn't Know

Cod: a fish that changed the world

Atlantic cod (Gadus morhua) is not just any fish. Along with herring, it is the fish that has most influenced human history. Wars, discoveries, commercial empires, and gastronomic traditions of dozens of countries revolve around this cold-water animal.

Mark Kurlansky, in his celebrated book "Cod: A Biography of the Fish that Changed the World," argues that without cod, there would have been no Viking trade routes, no industrial revolution in New England, and no Basque democracy. It may sound exaggerated, but historical data supports him.

Let's dive into 15 facts that will make you see this fish with new eyes.

1. It can live for over 25 years

Atlantic cod is a surprisingly long-lived fish. While most commercial fish live between 5 and 10 years, cod can exceed 25 years of life under natural conditions. Specimens up to 27 years old have been documented in Norwegian waters.

Its age is determined by counting the growth rings on its otoliths (small inner ear bones), similar to how tree rings are counted. Each ring represents a year of life. Older specimens are also the largest and produce the most eggs, making the protection of large adults crucial for the species' sustainability.

2. A female lays up to 9 million eggs

The reproductive capacity of cod is simply astonishing. A large adult female can release between 3 and 9 million eggs in a single spawning season. This figure makes it one of the most prolific fish in the ocean.

However, the survival rate is minuscule: it is estimated that less than one in a million eggs will reach adulthood. Eggs, larvae, and juveniles are prey to countless predators, from jellyfish to other fish. This reproductive strategy (many eggs, low survival) is typical of marine fish and explains why overfishing has such devastating effects: when the adult population is drastically reduced, the recovery capacity is very slow.

3. It's a voracious predator

Far from being a passive fish, cod is an active and opportunistic predator. It feeds on almost everything it finds: herring, capelin, shrimp, crabs, marine worms, squid, and even smaller cod (documented cannibalism).

An adult cod can consume up to 3% of its body weight daily. It has a large mouth with a prominent lower jaw and hundreds of small, sharp teeth. Its chin barbel (the "beard" under its jaw) contains chemoreceptors that allow it to detect prey in murky and dark waters.

4. The Vikings used it as currency

Norwegian Vikings discovered that cod, dried in the cold fjord air (stockfish), could be preserved for years without refrigeration. This dried cod became the foundation of their commercial empire starting in the 9th century.

Viking stockfish traveled from Norway to the Mediterranean, exchanged for spices, wine, olive oil, and precious metals. Dried cod literally functioned as currency: it had a stable value, was durable, transportable, and universally demanded. The Hanseatic League, the largest trade network in medieval Europe, was largely built on the trade of Norwegian cod.

5. Portugal has 365 cod recipes (one for each day)

Portugal is, along with Spain, the country that consumes the most cod in the world — even though it doesn't have its own cod fishing grounds. Portuguese tradition says that there are 365 ways to prepare bacalhau, one for each day of the year.

In reality, Portuguese cookbooks document more than 1,000 cod recipes. From the universally known bacalhau à Brás (shredded with straw potatoes and egg) to bacalhau com natas (gratinéed with cream) or bacalhau à Gomes de Sá (with potato, onion, and olives), cod is the soul of Portuguese gastronomy. Portuguese people call it "fiel amigo" (faithful friend) and it is the absolute protagonist of Christmas Eve dinner.

6. The largest specimen weighed 96 kg

Atlantic cod can reach impressive sizes. The largest specimen ever scientifically documented weighed 96 kg and measured 180 cm in length, caught in Norwegian waters in May 1895.

Today, due to fishing pressure, it is very rare to find cod weighing more than 20-25 kg. The average commercial catch size is between 2 and 10 kg. Large cod are increasingly scarce, which has raised concern among marine biologists: without large individuals producing millions of eggs, the recovery of populations slows down enormously.

7. It can live at a depth of 600 meters

Atlantic cod inhabits a surprising range of depths. Although it prefers waters between 30 and 200 meters, specimens have been found at depths of up to 600 meters. This adaptability allows it to occupy different habitats depending on the season, water temperature, and food availability.

In winter, cod migrate to deeper, colder waters to spawn. In summer, they move to shallower waters to feed. These seasonal migrations can cover distances of hundreds of kilometers and have been documented by electronic tagging.

8. Its swim bladder was used to make glue

The cod's swim bladder (the organ that regulates its buoyancy) has a high collagen content. Historically, it was processed to obtain isinglass, a gelatinous substance used as high-quality glue and as a clarifier for wines and beers.

Cod isinglass was the preferred adhesive of European luthiers for centuries. Stradivarius, Guarneri, and Amati violins were assembled with cod swim bladder glue. Today, some artisanal luthiers still use this traditional material for its flexibility and durability, superior to synthetic adhesives.

9. It caused a war between Iceland and the United Kingdom

The so-called "Cod Wars" were three conflicts between Iceland and the United Kingdom (1958-1976) over fishing rights in Icelandic waters. Iceland, whose economy depended almost entirely on cod, unilaterally extended its exclusive economic zone from 4 to 200 nautical miles.

Although they were called "wars," there were no deaths, but there were collisions between warships, cutting of trawl nets, and a diplomatic crisis that threatened to break NATO. Iceland won all three disputes, and its 200-mile model became the international standard enshrined in the United Nations Convention on the Law of the Sea (1982).

10. It's one of the few fish with a "beard"

Cod possesses a unique distinguishing feature: a chin barbel, a kind of "beard" that hangs from its lower jaw. This sensory appendage, present throughout the Gadidae family, is packed with chemoreceptors and mechanoreceptors.

The barbel allows cod to detect prey hidden on the seabed, "tasting" the water and sediments. It functions as an external tongue that complements its limited vision in the cold, murky waters where it lives. It is one of the easiest identifiers to distinguish cod from other white fish.

11. Its liver is more valuable than its meat

Cod liver oil was for centuries one of humanity's most important nutritional supplements. Rich in vitamins A and D and omega-3 fatty acids, it was used to prevent rickets (vitamin D deficiency) and strengthen the immune system.

In the pre-industrial era, cod liver was worth more by weight than the fish's meat itself. Norwegian and Scottish fishermen carefully separated the livers to sell them at a higher price. Today, cod liver oil remains a popular supplement in Nordic countries, where vitamin D deficiency due to lack of sunlight is endemic.

12. It was the first globalized fish

Long before the concept of "globalization" existed, cod was already traveling from one continent to another. From the 15th century onwards, salted cod became the first food traded on a global scale.

Basque fishermen pioneered cod fishing in Newfoundland (Canada) — some historians argue they arrived there before Columbus reached America. Basque salted cod fed Spanish, Portuguese, and English armies, was currency in the transatlantic triangular trade (along with slaves and sugar), and allowed European colonies in America, Africa, and Asia to be fed.

13. It can change color depending on the seabed

Cod has a limited but real ability to alter its coloration to blend in with its environment. Its natural color varies greatly depending on the habitat: cod living on rocky bottoms tend to be mottled brown, while those inhabiting sandy bottoms are lighter and greener.

This color change is not instantaneous like in an octopus or cuttlefish, but it occurs gradually over weeks when the fish moves to a new habitat. The chromatophores (pigment cells) in its skin expand or contract in response to environmental stimuli.

14. Spain consumes more cod than any other non-Nordic country

After Portugal, Norway, and Iceland, Spain is the largest per capita consumer of cod in the world. It is particularly popular in the Basque Country, Catalonia, and Galicia, where it is part of the regional gastronomic identity.

The Spanish tradition of cod has religious roots: for centuries, the Catholic Church prohibited meat consumption for up to 166 days a year (Lent, Fridays, vigils). Salted cod, which could be preserved without refrigeration, became the perfect substitute. Today, although religious reasons have disappeared, cod remains one of the most consumed fish in Spain, with emblematic recipes such as pil-pil, brandade, bacalao al ajoarriero or cod fritters.

15. Its population collapsed in 1992 and has not fully recovered

In July 1992, the Canadian government declared a total moratorium on cod fishing in the Grand Banks of Newfoundland. What had been the world's most productive fishing ground for 500 years had been emptied.

Industrial overfishing, with trawlers capable of catching more cod in an hour than a traditional boat in an entire season, reduced the population to less than 1% of its historical level. The 1992 moratorium represented the largest job loss in Canadian history: 40,000 people were left jobless overnight.

More than 30 years later, the Northwest Atlantic cod population has still not fully recovered. This collapse is today the most cited example in marine biology of the dangers of overfishing and the importance of sustainable management of marine resources.

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