Electrophoretic Analysis of Gizzard Shad from the Lower Mississippi River and Ohio

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Abstract
Horizontal starch gel electrophoresis was used to analyze allozyme variation among subpopulations of gizzard shad Dorosoma cepedianum collected from the Mississippi River near Eudora, Arkansas in May and September, 1980. Fish from five river habitats (dikefield, natural bank shoreline, revetment shoreline, abandoned channel, and oxbow lake) were compared to those taken from Acton Lake, Ohio and Lake Erie. Of the 32 enzyme and protein loci that were examined, only esterase‐2, 6‐phosphogluconate dehydrogenase, aspartate aminotransferase‐1, and hemoglobin were polymorphic. Chi‐square contingency analyses of allele frequencies showed homogeneity among the Mississippi River habitats; significant heterogeneity was observed between the Mississippi River and Ohio populations. Allele frequencies between male and female fish were homogeneous. However, the allele frequencies of the esterase‐2 locus were significantly different between age‐I and age‐II fish. Genic variation was estimated for gizzard shad from average heterozygosity (1.72–3.44%) and percent polymorphism (6.25–9.38%). The homogeneity of allele frequencies among the Mississippi River habitats and the low amount of genic variation may be related to the broad ecological niche of the gizzard shad.