Identification of species of fish by gradient-gel electrophoresis

An electrophoretic method is described for distinguishing between fish fillets according to their protein composition. Thaw fluid (4 microL) was applied to one of 14 sample positions of a precast gel, containing a gradient of polyacrylamide of either 2.5 to 27% or 3 to 40%. All reagents and gels are commercially available in ready-to-use form. Either gel provided a distinction between any of the 42 fish types, but the 3 to 40% gel gave better identification because of its superior molecular-sieving properties. Reproducible electrophoretic patterns were obtained for different samples of the same fish type, but small differences were shown for fish of widely different origin, for example Australian and New Zealand ling.