The scientific name for the Atlantic cod is Gadus morhua. This compound word has a double origin: 'Gadus' comes from the Greek "gados", meaning fish, while 'morhua' is derived from "morua" in Latin, meaning cod. This suggests that cod was known and highly valued by the Ancient Romans.
The origin of the word “bacalao“ (cod) is more uncertain. The Real Academia Española (RAE) dictionary states that it comes from the Basque word “bakallao“, which may in turn derive from the Dutch word “bakeljauw“.
There are around 60 species of cod, the most common of which in the North Atlantic is Gadus morhua. In turn, cod is part of a wider family of marine fish called Gadidae, from the order Gadiformes, which also includes hake. This family gives cod its more general features: a slender and elongated body, rounded tail, and thin caudal peduncle.
Cod possess a large mouth, small eyes, a barbel (or “beard“) below the lower jaw, a soft curving lateral line, three spineless dorsal fins, two pelvic fins, and a truncated caudal fin. Its skin is a greeny-brown colour, characterised by small specks on the upper part, and a whiteish belly. If found in an area with a lot of algae, its tones will vary to reddish. If found next to seagrass, the skin will become more greenish; or greyer if next to sandy seabeds.
Cod feed on smaller fish and are fairly selective in their choices. One of its favourite foods is the small fish capelin, but in times of scarcity it can feed on smaller fish from its own species. Although cod is a medium-sized fish (usually from 50 to 80 cm long and 4 to 5 kg), it can reach up to 90 kg in weight and 160 cm in length.
Its growth depends on the area in which it is found: the growth rate is lower in populations in the north, but greater in southern populations. It is thought that cod in populations in Canada can grow by around 10 cm per year. Most individuals reach sexual maturity between the ages of 6 and 8, and their average lifespan is 20 years. For this reason, they must be at least 30 cm in the North Sea and 35 cm in the Cantabrian Sea when fished.
Mature cod is one of the most fertile marine species; each female can lay between 1,000,000 and 18,000,000 eggs in successive batches. The spawning season occurs between winter and spring. In order to support this activity, cod feed intensively in summer and autumn. Cod populations usually migrate, forming large shoals. There are currently 11 populations or stocks in the Northeast Atlantic, and a few others in the Northwest Atlantic.
Cod is a cold-water species, and can be found in the North Atlantic, North Sea, Baltic Sea, as well as in the Bay of Biscay and the English Channel. However, the fishing grounds containing the greatest number of specimens are situated on both sides of the North Atlantic, from southern Canada to Newfoundland and the north of Greenland, and from Iceland via the North Sea to Norway and the Svalbard Archipelago. Cod usually lives at temperatures ranging from 2°C to 8°C, but can also be found at temperatures of up to 20°C.
It lives on muddy, sandy or gravelly marine beds. It is known as a 'demersal' species of fish because it lives very close to the sea beds. However, depending on the conditions of the water and its biological cycle, it can also live nearer the top. For example, in exceptional cases in the Baltic Sea, cod can often be found in the pelagic zone (open sea) due to a lack of oxygen at the bottom. In this way, although cod can be fished from a depth of between 1 and 600 metres, it is usually found at a range of between 10 and 200 metres.
Cod is a migratory species, and migrates annually from feeding grounds to specific spawning areas. Some of these migrations can be very long, up to 800 kilometres. The high season for cod fishing is therefore in winter and spring.
The most typical way to preserve codfish is to salt it. Salting is a very old method of preservation, which, alongside drying, took place on Bay of Biscay beaches for the first time during the Middle Ages. This discovery meant that more cod could be caught and traded than other fish.
Once caught, the fish changes rapidly due to the action of microorganisms, autolytic enzymes, chemical reactions (mainly in the presence of atmospheric oxygen) and physical processes. For this reason, salting has been used as a method of preservation for generations. Combining salting and drying methods creates a product that lasts even longer: the salted cod (bacalao) that we know today.
Cod is the main lean fish to be salted using the dry method. The quality of the final product depends on whether the process is followed properly, the quality of the salt, and the freshness of the cod itself.
Once caught, the fish usually bleeds to death and is kept cold until arriving at port. Salting takes place in the factory a few days after the catch. The cod is butterflied and distributed according to its weight, in order to apply the correct amount of salt. The fish are then stacked up, alternating layers of fish skinside down with layers of salt. The fish-to-salt ratio is usually 6/10. Once in contact with the salt, the cod begins to mature. This process lasts around three weeks. The fish is periodically restacked and new salt is added.
The purity of the salt concentration affects the organoleptic characteristics of the product, because if the salt penetrates and reduces its wetness quickly, this will prevent possible impurities, rancidity, or darkening on the surface. The calcium and magnesium salts produce a whiter product, but also give it a more bitter taste. Pure salt creates a softer, yellower product with a more intense flavour.
A mixture of fine, medium and coarse salt is recommended for the salting process. It is advisable to leave a small gap between the fish and the floor in order to help drain the brine that is gradually formed during the process. This helps to prevent the fish from becoming waterlogged on the lower layers and thus altering as a result of microbiological contamination. Moreover, the total height of the stacked fish should be no greater than 1.5 metres.
Drying the cod (semi-curing) takes place in drying rooms: The fish is brushed with coarse salt, fine salt is added, and the fish then proceeds to be dried in a forced air tunnel.
Bacalao (salted cod) produced this way offers white meat that is only slightly damp and has an intense flavour. It reacts very well to cooking, as it produces a lot of gelatine and thickens sauce very well. Despite various methods of conservation such as freezing, salted cod is still consumed in abundance because of its ever-changing flavour and texture. The meat of salted cod is presented in sheets or flakes that give it a unique texture compared to other fish.