Identification of freshwater fish commercially labelled "perch" by isoelectric focusing and two-dimensional electrophoresis

Isoelectic focusing (IEF) and 2-dimensional electrophoresis (2-DE) were used to distinguish 4 freshwater fish species which are sold under the generic label of "perch": Perca fluviatilis (European perch), Lates niloticus (Nile perch), Stizostedion lucioperca (European pike perch) and Morone chrysops x saxatilis (sunshine bass). These species have different com. values but are easily "interchangeable" because they are sold already filleted, in view of the numerous bones of the whole fish. IEF of the water-sol. proteins extd. from fish muscle resolved in species-specific patterns. Intra-species polymorphism was low, and did not concern the bands identified as characteristic of the species. As well, 2-DE maps showed numerous species-specific protein spots. Interestingly, while none of the IEF bands was common to all 4 species, several major 2-DE spots were similar. Therefore, IEF of water sol. sarcoplasmic proteins is sufficient to unambiguously discriminate among the 4 species considered. Anal. by 2-DE, which has a higher resoln. power but it is more expensive and time consuming, may be applied to obtain further knowledge of the proteome of poorly characterized species.