Atlantic cod

The Atlantic Cod can grow to 2 meters in length and weigh up to 96 kilograms (212 lb). It can live for 25 years and usually attains sexual maturity between ages two and four.  It has a colouring of brown to green, with spots on the dorsal side, shading to silver ventrally. A lateral line is clearly visible.   Its habitat ranges from the shoreline down to the continental shelf.  The   Atlantic cod   is labelled VU (vulnerable) on the IUCN Red List of Threatened Species. Several cod stocks collapsed in the 1990s (declined by >95% of maximum historical biomass) and have failed to recover even with the cessation of fishing.  Adult cod form spawning aggregations from late winter to spring. Females release their eggs in batches, and males compete to fertilize them. Fertilized eggs drift with ocean currents and develop into larvae.  Atlantic cod are a shoaling species and move in large size-structured aggregations led by larger scouts who lead the shoals direction, particularly during post-spawning migrations inshore for feeding. Cod actively feed during migration and changes in shoal structure occur when food is encountered.   Atlantic cod are apex predators and adults are generally free from the concerns of predation. Juvenile cod, however, may serve as prey for adult cod, which sometimes practice cannibalism. In the southern North Sea, 1 to 2% (by weight) of stomach contents for cod larger than 10 cm consisted to juvenile cod. In the northern North Sea, cannibalism was higher, at 10%. Other reports of cannibalism have estimated as high as 56% of the diet consists of juvenile cod.  Atlantic cod have been recorded to swim at speeds of a minimum of 2 to 5 cm/s and a maximum of 21 to 54 cm/s with a mean swimming speed of 9 to 17 cm/s. In one hour, cod have been recorded to cover a mean range of 99 to 226 square meters. Swimming speed was higher during the day than at night. This is reflected in the fact that cod more actively search for food during the day.