Choose the substitute based on dish type: sardines or salmon for grilling, herring or smoked trout for smoked dishes, canned tuna for cold salads, jackfruit or tofu for vegan options.
Prepare the substitute: drain canned fish or jackfruit; marinate tofu in seaweed broth for best flavor.
Use the substitute in a 1:1 ratio by weight or volume according to the substitute's notes.
Adjust seasoning to compensate for differences in saltiness or oiliness, especially with herring or tofu.
Taste final dish and ensure desired texture and flavor balance; add oils if needed for mouthfeel.