Identification of Pacific rockfish (Sebastes) species by isoelectric focusing

Isoelectric focusing (IEF) is currently the most reliable method available for the identification of fish species. The high resolution of this method usually allows discrimination between even closely related species. One genus, the Sebastes, does present a problem however. Using both low and high resolution, IEF is unable to differentiate several species. Disc electrophoresis, used in an AOAC official final action method, does not differentiate the rockfish reliably. Using IEF, identical protein patterns were obtained for Pacific Ocean perch (Sebastes alutus), Bocaccio rockfish (S. paucispinis), and yelloweye rockfish (S. ruberrimus). A second group, comprised of silvergray rockfish (S. brevispinis), yellowtail rockfish (S. flavidus), black rockfish (S. melanops), and canary rockfish (S. pinniger), also has identical protein patterns. Widow rockfish (S. entomelas) and chilipepper rockfish (S. goodei) each had a unique pattern, different from the above 2 groups and from each other. The actual taxonomic relationships of these rockfish species are not clear and further work with IEF may help in this regard. Users of IEF and disc electrophoresis for identification purposes should be aware of this problem when working with the Sebastes.