Genetic and meristic variations in the mummichog Fundulus heteroclitus, living in polluted and reference estuaries

Genetic and meristic variations were assessed in mummichogs (Fundulus heteroclitus) living in two sites downstream from a bleached kraft pulp mill in the Miramichi Estuary (Miramichi E.) (New Brunswick, Canada) and in four reference estuaries. Genetic variability detected by electrophoresis of enzymes was low except for EST-3. Geographic distribution of rare alleles at four loci, discontinuity in allelic frequencies at the EST-3* locus and differences in the estimated number of migrants indicated that F. heteroclitus does not form a panmictic population in the study area. Temporal variability in allelic frequencies at the EST-3* locus was detected only at the site closest to the mill (M1). The proportion of fish with high pelvic fin ray counts was consistently higher at site M1 and was correlated at all sites to the proportion of fish with asymmetric fin ray counts. The possible impact of the observed genetic discontinuity on the response of this sentinel species to pollutants should be considered in further studies.