Mackerel (saba) is a shiny silver skinned oily fish or hikarimono. Perennially popular, it is considered the quintessential autumn fish. Chub mackerel are in season from September to October in Japan when they reach their peak in size and fat content. Sujime, the process of curing fish in salt and marinating it in vinegar, is commonly used to keep mackerel meat firm and fresh.