This species is highly polymorphic and in Lake Thingvallavatn four phenotypic morphs have evolved (small benthic (SB), large benthic (LB), Murta (limnetic, M) and piscivorous limnetic (PI) morph).
Bleikjan í Þingvallavatni er mjög fjölbreytt, í vatninu finnast fjögur form; dvergbleikjan (e. small benthic: SB), murta (e. small limnetic: M), kuðungableikja (e. large benthic: LB) og sílableikja (e. piscivorous limnetic: PI).