Like a marine vacuum cleaner, the cod scours the sea bottom for edible morsels — shellfish, marine worms and fish all form part of its diet. This lifestyle is reflected in its appearance; from above the cod appears a mottled, neutral colour, making it very hard to spot against the sea bottom. Its back can vary from reddish brown to grey-green, depending on the type of sea bed and diet, while its belly is a whitish colour.
Follow the feeding
Cod are out and out predators and there is very little they won’t eat. When gutted, some have even been found to have munched their way through a plastic cup just before being caught! However, their usual diet consists of fish. Young cod up to two years old feed mainly on crabs and other crustaceans but as they grow they eat more fish. The large mouth enables these voracious feeders to swallow quite large prey – cod of 7 lb (3.2kg) can swallow whiting of over 1lb (0.45kg) whole!
In most areas of Britain there is a tendency for mature cod to follow the sprat shoals inshore during winter. Good shore fishing can be had at these times as they often feed right up to the water’s edge in pursuit of their prey. They also move to the shore after an onshore gale has stirred up the sea bottom, dislodging many prey species and providing a veritable feast for the hungry cod. Such heavy feeding tends to occur just before spawning, as the cod feed up in preparation, and again afterwards as they recover.
Cod inhabit the continental shelf. They are most common at 30-90m (100-300ft) and are rarely, if ever, found any deeper than 180m (600ft). They tend not to move very far from their spawning grounds, certainly no more than 100 miles (160km), which means that there are several fairly separate populations of cod around Britain, though these do overlap. These groups are to be found in the Irish Sea, West of Ireland, around the Hebrides, the North Sea, as well as towards the Kent and Cornwall ends of the English Channel.
Between January and April cod move into the deeper waters of their spawning-grounds. Up to nine million eggs are released by the female close to the sea bed where they are fertilised by the male. These eggs then drift slowly to the surface. However, only a small percentage of the larvae survive to become adults.
After about a year the codling – the name for young cod up to 6 lb (2.7kg) – move to nursery areas in shallow waters This explains the numbers of codling found around British coasts for most of the year. These fish move out to deeper waters once they mature at three to four years old. Being predominantly bottom-living fish, cod are shy of daylight. They mainly forage close inshore at night or at times when the sea is opaque (such as when the water is highly coloured after a storm) so these are good occasions for fishing.