Lead


Lay summary
Endocrine disruption in Switzerland: Assessment of fish exposure and effects (SAFE).

Endocrine disruption in Swiss brown trout.

Experts assume that endocrine disruptors have already left their mark on Swiss ecosystems and have contributed to population changes in wildlife. In this project the occurrence of these effects is studied in brown trout in specially selected Swiss rivers.

Background
The presence of endocrine disruptors is thought to have already had an impact on Swiss ecosystems and is suspected of being a factor contributing to population changes in wildlife. Earlier projects showed the presence, and in some cases also the effect, of estrogen disruptors on organisms in Swiss rivers. However, to date, the extent of these effects, and whether fish populations are being impaired, is still an open question.

Aim
This project aims to generate scientifically sound data to determine whether disturbances of the estrogen system of fish are occurring in wild fish populations in Switzerland. Firstly, the estrogen contamination of approx. 20 sites will be measured using one standard bioassay for river water samples, and the biomarker vitellogenin will be measured in wild brown trout. Secondly, wild trout from one of these rivers will be studied in detail for disturbances of their estrogen system. We will also explore whether the brown trout population in this river has been disturbed with respect to fertility, age structure or the size of the population. To enable comparison, critical life stages, such as hatchlings or mature fish, will also be studied for their response to estrogens in laboratory experiments. In a future project we will integrate these data into a population model to assess the importance of these changes on the fish population.

Significance
Catches of brown trout in Swiss rivers and streams have decreased by 60% during the last 20 years. The results of the current project should allow better assessment of the role of estrogenic disruptors in this context. This will be of great importance for other countries in which declining fish catches and populations have been observed. The results of the project should therefore have an impact on the management of aquatic ecosystems and fish resources.