page_title: Cod
section_title: Ecology
hierarchical_section_title: Cod / Ecology
caption_attribution_description: Lernaeocera branchialis (Linnaeus, 1767) &amp; Merlangius merlangus (Linnaeus, 1758) English: A parasitical copepod on a Whiting, from the Belgian coastal waters (Kwintebank). Length (including egg sacks): ~14 mm. Lab image. Français&#160;: Lernaeocera branchialis, un copépode parasite récolté sur un Merlan (Merlangius merlangus). Longueur (œufs compris)&#160;: 14&#160;mm. Photo prise au laboratoire.
context_page_description: Cod is the common name for the demersal fish genus Gadus, belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus Gadus is commonly not called cod.
  The two most common species of cod are the Atlantic cod, which lives in the colder waters and deeper sea regions throughout the North Atlantic, and the Pacific cod, found in both eastern and western regions of the northern Pacific. Gadus morhua was named by Linnaeus in 1758.
  Cod is popular as a food with a mild flavour and a dense, flaky, white flesh. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E, and omega-3 fatty acids. Young Atlantic cod or haddock prepared in strips for cooking is called scrod. In the United Kingdom, Atlantic cod is one of the most common ingredients in fish and chips, along with haddock and plaice.
context_section_description: Adult cod are active hunters, feeding on sand eels, whiting, haddock, small cod, squid, crabs, lobsters, mussels, worms, mackerel, and molluscs.
  In the Baltic Sea the most important prey species are herring and sprat. Many studies that analyze the stomach contents of these fish indicate that cod is the top predator, preying on the herring and sprat. Sprat form particularly high concentrations in the Bornholm Basin in the southern Baltic Sea. Although cod feed primarily on adult sprat, sprat tend to prey on the cod eggs and larvae.
  Cod and related species are plagued by parasites. For example, the cod worm, Lernaeocera branchialis, starts life as a copepod-like larva, a small free-swimming crustacean. The first host used by the larva is a flatfish or lumpsucker, which it captures with grasping hooks at the front of its body. It penetrates the fish with a thin filament, which it uses to suck the fish's blood. The nourished larvae then mate on the fish. The female larva, with her now fertilized eggs, then finds a cod, or a cod-like fish such as a haddock or whiting. There the larva clings to the gills while it metamorphoses into a plump sinusoidal wormlike body with a coiled mass of egg strings at the rear. The front part of the worm's body penetrates the body of the cod until it enters the rear bulb of the host's heart. There, firmly rooted in the cod's circulatory system, the front part of the parasite develops like the branches of a tree, reaching into the main artery. In this way, the worm extracts nutrients from the cod's blood, remaining safely tucked beneath the cod's gill cover until it releases a new generation of offspring into the water.
caption: A fish with its gills infested with two cod worms
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