A non-synonymous single nucleotide polymorphism (SNP) underlies a diallelic allozyme polymorphism at the mitochondrial NADP-dependent mMEP-2* locus in Atlantic salmon (\textit{Salmo salar} L.). The resultant amino acid substitution, which alters the charge of the allelic products, matches the differential mobility of the two allozyme alleles, while allozyme and SNP assays revealed genotyping concordance in 257 of 258 individuals. A single mismatch, homozygous allozyme vs heterozygote SNP, suggests the presence of a second, less common null allele