Immunoassays have been developed to facilitate authenticity testing of fish and seafood products. Three specific authenticity issues were addressed: substitution of canned sardine with other species, adulteration of canned tuna with bonito and adulteration of reformed crustacean meat with white fish. Antisera were raised to water‐soluble protein extracts of canned sardine and canned tuna and, where appropriate, their specificities were adjusted using simple blocking and/or immunoadsorption methods. The antisera were used to construct several immunoassays, one of which allowed discrimination between canned sardine and non‐sardine meat, and could be used to detect substitution of whole sardines with non‐sardine species. A second set of assays allowed discrimination between fish and crustacean meat, and should allow the detection of fish in crustacean products. However, with a third set of immunoassays, only limited discrimination between bonito and tuna could be achieved and these assays require further development.