Monitoring of metal concentrations in fish is commonly conducted using samples of fish liver or muscle. This becomes problematic when these values are used for environmental status evaluations regarding chemical pollution, as many of the thresholds evaluating environmental status are designed to evaluate concentrations in whole-fish.

In this study, concentrations of cadmium, lead, and mercury in herring and perch are compared between liver, muscle, and whole-fish. The aim is to create conversion factors that can be used to convert metal concentrations between tissues and organs.

Mercury and cadmium were detected in all analyzed organs and tissues, whereas lead concentrations were below the level of quantification for most muscle and liver samples. In general, there was a strong relationship between liver and muscle concentrations and concentrations in whole-fish, indicating that creation of conversion factors between tissues and organs is suitable.

The resulting conversion factor between whole-fish and liver concentrations for cadmium was 0.1 and 0.16 for herring and perch, respectively. The conversion factor between whole-fish and liver concentrations for mercury was 0.52 and 1.66 for herring and perch, respectively, while for whole-fish and muscle concentrations for mercury, the conversion factor was 0.86 and 0.74 for herring and perch. As there was no significant relationship between liver and whole-fish concentrations for lead, a conversion is not appropriate. Conversion factors levels differed significantly between herring and perch, indicating that species-specific conversion factors are necessary.