Fish populations

Population studies carried out over many years take dynamic processes and fish responses into account. Density and biomass change over time.

We are examining the temporal pattern of population fluctuations, using studies on population dynamics. We focus particularly on brown trout populations.

Current projects

Population dynamics and reproduction of brown trout in the River Lützelmurg: effects of hormonally active substances

Hormonally active substances (endocrine disruptors – natural and synthetic chemicals, which are capable of disrupting the hormonal system) have long been suspected to be partly responsible for anomalies during sexual development and decreasing fishing yields. Reports, especially from England, but also from Switzerland, make a connection between the feminisation of male fish and wastewater from sewage treatment plants. To date, only little is known about the behaviour of hormonally active substances in the environment and their effects on organisms, in particular, on populations. The SAFE project (“Endocrine disruption in Switzerland: assessment of fish exposure and effects”), which is a part of the national research programme NRP50, addresses these issues.

The study at the Lützelmurg aims to determine the effects of hormonally active substances on the fish fauna and, in particular, on the population dynamics and reproduction of brown trout. The results gained will be used to determine better the role of hormonally active substances as a potential cause of the decrease in fish yields.

• Contact person: Sara Schubert (PhD thesis), Armin Peter
  
• Funding: SNFS, Eawag, University of Basel
  

Publication

• Schubert, S., A. Peter, R. Burki, R. Schönenberger, M.J.-F. Suter, H. Segner & P. Burkhardt-Holm. 2008. Sensitivity of brown trout reproduction to long-term estrogenic exposure. Aquatic Toxicology 90:65-72.