Caught in local waters and sold in a local market or directly from a boat to the consumer.
This is the freshest fish but volume is very low and you need to live near a local harbour in order to buy. It is boat-caught and returned to shore within a day normally frozen and then sold fresh to you within 2 days of catching.
Fresh fish, which is caught and landed at main UK ports gets sold through the normal distribution chain. This is perceived as fresh fish but it can spend a long time within the food chain before it is sold fresh to you, the consumer, especially with modern chilling techniques.
Boat-caught, allowing sailing to fishing grounds of 3 days, fishing for 3-7 days and 3 days sailing to return to the port. Fish can be 10 days old by the time it reaches a harbour. Later it is sold at market, processed and distributed to the shops within 4 days. Then it is sold as fresh to the consumer up to 14 days (2 weeks old) after being caught, but can be longer depending on packaging and shelf life.
Chilled fish is often frozen fish, which has been defrosted and is then distributed through the chilled food chain. Follows the same chain as fresh and frozen fish. Predominantly frozen fish sold on the defrost. Sold chilled to the consumer.