Sardine canning production line
The “oily fish” like sardine, herring, mackerel (and tuna, salmon etc.) are prime choices for canning because they are much better in that form than lean fish. They are also popular because they are some of the best fish to eat, health-wise, and before that was fully understood by science, they were still very nourishing and much cheaper than fresh leaner fish. Another reason is that sardine and mackerel Sardine canning production line are very fragile fish (they spoil faster than many other fish). Nowadays with modern technology they travel much better and can be found more widely in fresh form, but traditionally they didn’t fare so well or for very long away from their fishing areas, and they had to be preserved to be sold inland. Salted/cured (which are still used too) made way to canning in oil or brine eventually. This doesn’t exist only in Western countries, by the way. Even in Asia the “oily fish” are very popular as canned fish - and in Japan for instance you’d also find canned mackerel, sardine etc.