Use of sex ratio of bream (Abramis brama L.) as an indicator of endocrine effects: Results from the German Environmental Specimen Bank

In field monitoring, sex ratio as an endpoint of possible endocrine effects at population level can only be recorded as the deviation from the natural sex ratio. Unfortunately, data on natural sex ratios of many species cannot be used to control for such effects. This also applies to bream (Abramis brama L.), an important fish species in passive biomonitoring. Here we show that in natural bream populations the sex ratio decreases with increasing age. Age class specific correction coefficients were derived to eliminate age-dependency of the sex ratio.