Sigsy, mackerel horrible things, taste awful, but if you do want to keep some for eating, keeping them in a cold fridge for a couple of days will be ok, after that freeze and the quicker you can freeze them the better, if you have a super freeze on your freezer use it. Another thing, use a good quality cling film and wrap them up well, two or three layers, dont let any flesh be left uncovered or it will suffer freezer burn. If you do it properly you can keep mackerel quite a while. But as they are horrible tasting you had far better just give me all your mackerel.