The use of bioindicator fish species in monitoring programmes is widely accepted as a means of assessing marine environmental health. In such approaches, the effects of pollutants and other anthropogenic impacts on the health of individual fish is evaluated and compared to that of non-exposed reference fish. However, not all fish are the same. Genetic diversity between individuals translates into variance on how and when individuals respond to pollution, and the combined response of interbreeding individuals is reflected on how a population is affected by exposure to environmental stressors such as pollutants.
Whether due to natural causes or the result of previous pollution exposure and selection, some populations may be more tolerant to pollutant exposure than others. If not corrected, comparisons of disease profiles among populations with differing pollution tolerance levels will affect the interpretation of results from biomonitoring programmes.
In the UK, dab, Limanda limanda, and flounder, Platichthys /Jesus, are routinely used as environmental bioindicators of pollutant exposure; however, little information exists on population structuring among sampling locations. Here, the development of neutral microsatellite markers for dab and flounder is described. A novel approach for reducing the cost of labelling microsatellite primers in combination with multiple amplification of several loci in a single tube is then devised. Next, the development and preliminary evaluation of adaptive genetic markers to detect selection imposed by pollution is reported. No definitive
evidence of strong and recent selective pressures at the analyzed genes is found, but suggestions for future research are made. Estimating genetic differentiation between populations is central in population genetic studies. Several new and traditional estimators of genetic differentiation are compared empirically. Consecutively, the genetic structure of dab around the British Isles is analysed and described. Two main dab subpopulations, subtly but significantly differentiated, have been identified, corresponding to the North Sea and Irish Sea basins, though there is also evidence of structuring at other scales. The implications for biomonitoring programmes are considered. Finally the combination of both genetic and biomonitoring information is explored. No evidence of increased relatedness or inbreeding among individuals afflicted with liver nodules is found, however, for some samples with abnormally high frequency of liver nodules, the incidence can be explained by recent
immigration from other locations. Genotyping of assessed individuals provided important information not available by other means and the incorporation of population genetic data is encouraged for biomonitoring programmes studying mobile species.