My dad used to go cockleling in the late seventies and early eighties between Leasowe and Harrison Drive, and there was an abundance of them.
If I remember correcly, it was banned for a long time because the Mersey was so full of s**t.
You need a permit to do it now.
Also, it says it is closed for cockles at the moment but the West Kirby Mussel Bed is open.
BYELAW NWSFC 13A - COCKLES AND MUSSELS - MANAGEMENT OF THEFISHERY. Byelaw confirmed 29.03.96
1. The Committee, may close any cockle (Cerastoderma edule) or mussel (Mytilis edulis) bed or part of a bed for the purposes of fishery management or for controlling the rate of exploitation with regard to cockles and mussels.
2. Such closure shall be for a specified period and be undertaken only after the Joint Committee has consulted such persons or bodies appearing to them to represent local cockle or mussel fishermen, and provided the Committee has been advised by fishery scientists who appear to them to be suitably qualified, as to the need for such action.
3. No person shall, without the consent of the Committee, under the written authority in that behalf signed by the Clerk, remove, take or disturb any cockle or mussel from a bed or part of a bed of cockles or mussels which has been closed pursuant to this byelaw."
https://www.nw-ifca.gov.uk/cockle-fisheries/