Mackerel bap is an English fish sandwich originating from River Cottage Canteen restaurant in Axminster, where it's been created by chef Tim Maddams. The sandwich is made with mackerel fillets that are dredged in flour, dipped in beaten eggs, deep-fried in hot oil until golden and crispy, and then placed in a bread roll (bap) with tartare sauce or some mayonnaise with lemon juice.
However, mackerel is no longer considered sustainable by the Marine Stewardship Council, so the customers should be advised that the fish is no longer sustainable, and they can make the informed choice to eat mackerel baps or not, or try alternative dishes such as cod baps or kipper baps.